Casaabiertaaltiempo

Casaabiertaaltiempo
UNIVERSIDAD AlJTONOMA METROPOLITANA- IZTAPALAPA
/
D I S E Ñ O E I M P L E M E N T A C I O N DE UN S I S T E M A DE MONITOREO DE
I N T E R C A M B I O GASEOSO E N P L A N T A S
/MARTHA
REFUGI
/
POSADAS
P R O Y E C T O
P r e s e n t a d o como requisito
para obtener
e l grado de:
/
L I C E N C I A T U R A
E N
I N G E N I E R I A BIOMEDICA
Av. Michoacán y Purísima. Col. Vicentina. Iztapalapa. D.F. C.P. 09340. Tel. 686-03-22
I
E s t e p r o y e c t o f u e r e a l i z a d o en e l L a b o r a t o r i o d e F i s i o t e c n i a en e l Centro d e G e n é t i c a d e l C o l e g i o d e P o s t g r a d u a d o s
b a j o l a d i r e c c i ó n d e l D r . V e c t o r A . González Hernández, acept a d o como r e q u i s i t o p a r a l a o b t e n c i ó n d e l g r a d o d e :
LICENCIATURA
EN
I N G E N I E R I A BIOMEDICA
A S E S O R I N T E R N O (UAM):
A S E S O R EXTERNO ( C P ) :
Chapingo,
M.C.
MA. ESTHER D I A Z T R E V I R O
D R . V I C T O R A . G O N Z A L E Z HERNANDEZ
México,
Septiembre de 1988.
882155
A G R A D E C I M I E N T O
A todas aquellas personas que estuvieron
cerca d e m i
y que de alguna u otra m a n e r a contribuyeron e n este
trabajo.
CONTENIDO
Pág.
.
INDICE DE FIGURAS
.
.
INDICE DE ANEXOS.
I. INTRODUCCION.
.
1.1 EL INTERCAMBIO GASEOSO .
Conceptos Generales. . .
INDICE DE CUADROS
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Sistemas de análisis de gases.
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.......
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Unidad de suministro y acondicionamiento
de aire
.................
Cámara de asimilación . . . . . . . . . .
Sistema de muestre0 del gas . . . . . . .
Configuraciones de sistemas de análisis de
gases.
-
1.2
...................
Sistema cerrado . . . . . . . . . . . . .
Sistema abierto . . . . . . . . . . . . .
LA FOTOSINTESIS Y TRANSPIRACION COMO PROCESOS
DIFUSIVOS.
..
.
.......
Capa frontera . . . . . . . . . . . . . .
Estomática. . . . . . . . . . . . . . . .
Naturaleza de las resistencias
1.3
METODOS DE MEDICION DE COZ Y VAPOR DE AGUA
.
..............
Analizador de gases de rayos infrarrojos
(IRGA). . . . . . . . . . . . . . . . . .
Principio. . . . . . . . . . . . . . .
Construcción . . . . . . . . . . . . .
Calibración. . . . . . . . . . . . . .
Medición del COZ
i
iv
vi
viii
1
3
3
4
4
4
7
8
8
11
12
14
14
15
16
16
16
16
18
20
Pág.
Calibración absoluta
.......
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Medición del vapor de agua . . . . . . .
Física del vapor de agua. . . . . .
Temperatura de punto de roclo. .
Calibración diferencial.
Déficit de saturación.
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Sensores de humedad . . . . . . . . . . . .
Psicrometrla de bulbo hGmedo y seco. . .
Sensores de humedad relativa . . . . . .
Higrometría de punto de rocío. . . . . .
Humedad relativa
11. DISEfJO E IMPLEMENTACION DEL SISTEMA DE MEDICION
....................
Características del sistema. . . . . . . . . . .
Determinación de l a tasa fotosintética (FC02). .
Determinación de la tasa transpiratoria (TT) . .
Descripción del sistema. . . . . . . . . . . . .
Sensores de COZ y vapor de agua . . . . . .
Sensor de COS. . . . . . . . . . . . . .
Sensor de humedad. . . . . . . . . . . .
Sistema de muestre0 del gas . . . . . . . .
Sistema de acondicionamiento del aire . . .
Cámara de asimilación . . . . . . . . . . .
1II.PRUEBA DEL SISTEMA . . . . . . . . . . . . . . .
Evaluación de la cámara sin planta . . . . . . .
DE GASES
Mediciones hechas en planta de maíz y cártamo.
.
Evaluación experimental de la resistencia de capa
frontera (ra).
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-I
--?
--"--
_ I -
20
21
22
22
22
22
23
24
24
26
27
28
28
28
30
30
30
30
32
32
33
34
36
36
38
43
Pág.
Cálculo d e l a r e s i s t e n c i a e s t o m a t a l
50
M e d i c i ó n d e tasa t r a n s p i r a t o r i a y o t r o s parámetros
c o n b a s e e n porometría.
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52
Cálculo d e l a r e s i s t e n c i a e s t o m a t a l (rs) con b a s e
en porometría
54
IV. CONCLUSIONES.
V.
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BIBLIOGRAFIA.
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57
58
I N D I C E DE CUADROS
Cuadro
1
Pág.
M e d i c i o n e s h e c h a s a l a cámara d e a s i m i l a ción s i n planta.
37
E v a l u a c i ó n d e l a cámara s i n p l a n t a .
38
M e d i c i o n e s h e c h a s a una p l a n t a d e m a í z .
39
M e d i c i o n e s h e c h a s a una p l a n t a d e c á r t a m o .
40
Tasas t r a n s p i r a t o r i a s (TT)
promedio a d i s -
t i n t o s f l u j o s d e a i r e a t r a v é s d e l a cámara
-
d e a s i m i l a c i ó n e n una p l a n t a d e m a í z y c á r -
41
tamo.
6
M e d i c i o n e s h e c h a s a un s í m i l d e p l a n t a d e
45
maíz de papel f i l t r o .
7
M e d i c i o n e s h e c h a s a un s í m i l d e p l a n t a d e
cártamo de p a p e l f i l t r o .
8
Tasa d e e v a p o r a c i ó n (TE)
46
a distintos flujos
d e a i r e a t r a v é s d e l a cámara d e a s i m i l a c i ó n
e n un s i m i l d e p l a n t a h e c h o c o n p a p e l f i l t r o . 47
iv
Cuadro
9
Pág.
R e s i s t e n c i a d e l a c a p a f r o n t e r a (ra) a
distintos flujos a través d e la cámara
de* a s i m i l a c i ó n e n u n s í m i l d e planta d e
m a í z y cártamo h e c h o s c o n papel filtro.
48
10
R e s i s t e n c i a e s t o m a t a l (r ) .
51
11
V a l o r e s o b t e n i d o s d e TT y o t r o s parámetros
S
c o n b a s e e n porometría.
12
53
R e s i s t e n c i a e s t o m a t a l (r ) c o n b a s e e n
S
54
porometría.
-
V
I N D I C E DE F I G U R A S
Figura
Pág.
1
Sistema de análisis de gases.
2
Diagramas de las dos configuraciones
5
más usuales para los sistemas de aná-
9
lisis de gases.
3
Modelo eléctrico de la hoja que ilustra
el proceso difusivo del C02.
13
Construcción de un analizador de gases
4
-
de rayos infrarrojos ( I R G A )
con cámaras
de absorción en paralelo.
5
19
Carta psicrométrica ilustrando las relaciones entre temperatura de bulbo seco y
temperatura de bulbo húmedo, humedad relativa (RH), razón de humedad y presión
de vapor.
25 .
6
Diagrama de bloques.
31
7
Cámara de asimilación.
35
vi
Figura
8
PSg.
Tasa t r a n s p i r a t o r i a (TT)
a distintos flu-
j o s d e a i r e a t r a v é s d e l a cámara d e asim&
l a c i ó n en una p l a n t a d e m a í z y c á r t a m o .
9
Tasa de evaporación (TE)
l a capa f r o n t e r a ( r a ) .
42
/ R e s i s t e n c i a de
49
I N D I C E DE ANEXOS
Anexo
1
Tabla meteorológica Smithsoniana No. 108.
2
Información técnica del analizador de gases
de rayos infrarrojos marca Beckman, Modelo
865.
3
Información tdcnica del higrómetro de punto
-
de rocío marca EGG Environmental Equipment,
Modelo 660.
4
Manual de operaciones e instrucciones de man
tenimiento de las bombas de vacío marca Felisa,
Modelos 1500 y 1600.
5
Manual de instrucciones de instalación y operación de l o s flujómetros marca Dwyer, series
RMC y V F B .
viii
1
1
I.
INTRODUCCION
Las plantas constituyen los elementos fundamentales para
la transformación de la energía radiante a energía qufmica a
través de la fotosíntesis, que es la base del proceso productivo en la agricultura.
La eficiencia en la producción de un
cultivo depende de cuanta energía química se elabora y que
proporción de esa energía se transforma en productos de impof
tancia económica para el productor, lo cual a su vez, es función del genotipo y de la disponibilidad de factores ambientales en cuanto a cantidad, calidad y oportunidad.
Ortiz
e$ al. (1985).
- Estos mismo autores señalan que durante el desarrollo de
una planta, existen numerosos pasos bioquímicos y físicos-químicos que se integran a través de esquemas complejos que originan procesos fisiológicos, como son la fotosíntesis, la respiración, la absorción y el transporte de minerales, la transpiración, la floración y otros muchos.
L a obtención de altos
rendimientos económicos requiere de la optimización de dichos
procesos, cuya expresión es determinada genéticamente y modificada por los factores ambientales.
Estos Cltimos pueden ser
manipulados por el hombre a través de las prácticas culturales
(fertilización, control de plagas, riego, etc.)
afectando de
esta manera al microclima en el sistema agrícola bajo producción; es decir se afecta l a circulación de C o p , la humedad relativa
y
la temperatura; se modifica la penetración de energía
2
radiante,
tética.
alterándose l a e f i c i e n c i a de l a actividad fotosin-
De e s t a f o r m a ,
pueden a p r e c i a r s e l a s abundantes re-
l a c i o n e s e n t r e los p r o c e s o s f i s i o l ó g i c o s y los f a c t o r e s ambientales.
En l a a c t u a l i d a d e x i s t e i n s t r u m e n t a c i ó n y m é t o d o s q u e
b a j o c o n d i c i o n e s a m b i e n t a l e s c o n t r o l a d a s s o n c a p a c e s d e monit o r e a r p r o c e s o s como l o s a n t e s d e s c r i t o s ,
dentro de los cuales
s e d e b e o p t a r p o r a q u e l l o s q u e además d e ser p r e c i s o s , r e s u l t e n á g i l e s y p e r m i t a n l a e v a l u a c i ó n d e un número d e p l a n t a s
q u e r e p r e s e n t e n a l a s p o b l a c i o n e s q u e se r e q u i e r e n a n a l i z a r .
Por l o anterior,
e 1 , o b j e t i v o de este proyecto c o n s i s t i ó
e n d i s e ñ a r e i m p l e m e n t a r un s i s t e m a p r e c i s o y á g i l p a r a m e d i r
el i n t e r c a m b i o g a s e o s o e n p l a n t a s ; e s d e c i r , l a m e d i c i ó n d e l
f l u j o gaseoso entre l a planta y l a atmósfera,
-
producido a t r a
vés d e l a f o t o s í n t e s i s ( f i j a c i ó n C o n ) y l a t r a n s p i r a c i ó n (péf
d i d a d e agua en forma d e v a p o r ) ;
l o q u e p e r m i t e t e n e r una es-
t i m a c i ó n d i r e c t a d e l a m a g n i t u d y e f i c i e n c i a d e ambos p r o c e -
sos.
3
1.1
EL I N T E R C A M B I O G A S E O S O
Conceptos Generales
E l intercambio de gas f o t o s i n t s t i c o
(C02),
se r e f i e r e a l
f l u j o de gas e n t r e l a p l a n t a y l a atmósfera producido a 'través d e
l a f o t o s í n t e s i s , l o q u e p r o p o r c i o n a una m e d i d a d i r e c t a
de e s t e proceso.
S i m u l t á n e a m e n t e se pueden h a c e r m e d i c i o n e s
d e l v a p o r d e agua y
02,
l o s c u a l e s también son parámetros que
proporcionan información sobre l a s limitaciones d e l proceso
fotosintético.
En l a a c t u a l i d a d e x i s t e n m é t o d o s e i n s t r u m e n t a c i ó n q u e
p e r m i t e n m o n i t o r e a r c a m b i o s muy p e q u e ñ o s e n l a c o n c e n t r a c i ó n
-
d e C O Z p r o d u c i d o s e n una a t m ó s f e r a d a d a p o r una p l a n t a c o m p l e ta,
una h o j a o un s e g m e n t o d e h o j a .
E s t a s m e t o d o l o g i a s pue-
den s e r usadas p a r a e s t u d i a r l a c o n t r i b u c i ó n f o t o s i n t é t i c a d e
l a p l a n t a o d e Ó r g a n o s d e l a misma ( e n d i f e r e n t e s e t a p a s d e
su d e s a r r o l l o o b a j o d i f e r e n t e s c o n d i c i o n e s a m b i e n t a l e s ) a
l a productividad,
e n d i v e r s o s campos o a m b i e n t e s c o n t r o l a d o s
en e l L a b o r a t o r i o .
E l m é t o d o más p r e c i s o p a r a m e d i r e l i n t e r c a m b i o d e CO,,
e s m e d i a n t e e l uso d e un a n a l i z a d o r d e g a s d e r a y o s i n f r a r r o jos
(IRGA:
I n f r a Red Gas A n a l i z e r ) .
La c a n t i d a d de C O P asimk
l a d o p o r l a p l a n t a p u e d e s e r m e d i d o s i S s t a s e a i s l a e n una
L@"
I Z T P P A L A P
d
SERYlCtOS DOCUMErCrMEQ
4
cámara, haciendo pasar un flujo de aire y detectando el cambio de concentración de C O Z en la atmósfera de la misma. Long
(1982).
Sistemas de Análisis de Gases
Los sistemas abiertos de análisis de gases, y l o s sistemas cerrados de flujo circulante, consisten de cuatro partes
fundamentalmente:
una unidad de suministro y acondicionamien
to de aire, una cámara de asimilación, la red de tuberías para gas y el sensor del gas a medir
(COZ
y/o
vapor de agua),
(Figura 1 ) .
Unídad de suministro y acondicionamiento de aire.
-El aire que circula a través de la cámara de asimilación
puede ser tratado previamente para tener l o s niveles de concentración de CO
y en algunos casos de O
,
humedad y tempera
tura previamente determinados, puede ser aire natural homogeneizado.
En ambos casos, se requiere conocer con la mayor
precisión tales características para asegurarse que el ambieo
te dentro de la cámara de asimilación es adecuado.
Esta uni-
dad incluye bombas de presión-vacío, tubería, flujómetros y
el equipo acondicionador u homogeneizador del aire.
CImara de Asimilación.
Una cámara de asimilación, no
es
más que un recinto ais-
lado y transparente donde se introduce la planta completa
o
5
@
VOOI0
\
L
A
M
b
I
L
N
T
a
t!
FIGURA I . Slstemo de A&lisk
de
008m8,
I-
.I
. ’. .
,.I
,
.<
~
,
6
p a r t e d e e l l a para o b t e n e r i n f o r m a c i ó n acerca d e l a s tasas d e
i n t e r c a m b i o g a s e o s o , ya sea f o t o s í n t e s i s o t r a n s p i r a c i ó n .
Es
-
t a s cámaras s o n u t i l i z a d a s e n d o s f o r m a s p r i n c i p a l m e n t e :
En e l l a b o r a t o r i o , l a s p l a n t a s s e a i s l a n e n d i c h a s cáma-
r a s para i n v e s t i g a r l o s n i v e l e s d e e s o s p r o c e s o s f i s i o l ó g i cos, mediante l a observación de l a respuesta de s u intercamb i o g a s e o s o y e l b a l a n c e d e e n e r g í a e n un a m b i e n t e " c o n t r o l a en f u n c i ó n d e l o s cambios que se produzcan en e l ambien-
do";
te externo a l a planta (radiación,
t e m p e r a t u r a , humedad, con-
c e n t r a c i o n e s d e C O Z y 0 2 ) o e l a m b i e n t e i n t e r n o d e l a misma
(contenido de sal y azúcar, n i v e l hormonal, estado h í d r i c o de
l a planta, etc.).
En e l c a m p o , l a s p l a n t a s s o n a i s l a d a s e n cámaras p o r t á t i l e s p a r a p r u e b a s donde se d e s c r i b e n c o m p o r t a m i e n t o s f i s i o -
l ó g i c o s generalmente en respuesta a variaciones naturales d e l
ambiente,
E l o b j e t i v o . d e t a l e s e x p e r i m e n t o s es p o d e r d i l u c i d a r
c i e r t o s p r o c e s o s e n c o n d i c i o n e s que s i m u l e n l a s n a t u r a l e s ,
p e r o q u e p u e d e n s e r t a n a r t i f i c i a l e s como e l i n v e s t i g a d o r l o
desee.
L a s c o n d i c i o n e s a m b i e n t a l e s d e n t r o d e l a cámara, p a r -
t i c u l a r m e n t e e l movimiento d e l aire y e l f l u j o de r a d i a c i ó n
(de onda c o r t a y l a r g a ) ,
nunca podrán ser i d é n t i c a s a l a s na-
t u r a l e s ; s i n e m b a r g o , p u e d e n s i m u l a r s e e n f o r m a muy p a r e c i d a .
A
7
El diseño de una cámara de asimilación dependerá del tamaño y forma del material vegetal a investigar, y del grado
de control deseado en factores como la concentración de C o p y
vapor de agua, la temperatura y la energía radiante, todos
ellos en relación con el movimiento de aire a través de la
C&
mara de asimilación.
A s í pues, es deseable que las condiciones ambientales que
estén afectando a la fotosíntesis
y la transpiración, y por
ende a la planta, sean conocidas y de preferencia estén bajo
el control del investigador.
incluyen:
Estas condiciones ambientales
-
la densidad de flujo de la radiación fotosintgtica
mente activa(que
es aquella que tiene una longitud de onda en-
tre 4 0 0 a 700 rim), incidente sobre la hoja de todas las dire2
cienes, temperatura de la hoja, concentración de C 0 2 , 02, vapor de agua, y presión y flujo del aire en la cámara.
Adicio
-
nalmente, es conveniente lograr una distribución homogénea
del aire circulante dentro de la cámara para evitar gradientes
indeseables.
Sistema de muestreo del g a s .
Muestras del aire circulante deben ser transferidas al
sensor de C 0 2 o de vapor de agua en el estado requerido; es
decir, con la cantidad, temperatura, presión, humedad y pureza adecuadas.
El sistema de muestreo puede variar considera-
blemente en estructura.
Generalmente cuando se usa en la me-
,
8
dición del intercambio d e C 0 2 en plantas, este sistema está
compuesto por: tubería, hiombas de presión-vacío, flujómetros,
reguladores de presión
y
dispositivo de secado de aire con
filtro y, válvulas; para medición de transpiración se pueden
usar además filtros para impurezas.
Configuraciones de sistemas de anslisis de gases
Existen varias configuraciones para la implementación de
un sistema de an’álisis de gases.
Dos de ellas son las más
usuales: sistema cerrado y sistema abierto.
S i s t e m a cerrado.
Este sistema descrito por Long (1982) es el más simple y
el más apropiado para trabajos de laboratorio con bajo costo,
sin requerir mucha especialización en técnicas de análisis de
gases; también trabaja con la menor sensibilidad del sensor del
gas a medir ( C o p
o
VA).
En un sistema cerrado, el aire fluye
de la cámara de asimilación hacis el sistema de tubería del sen
s o r ; después el aire es reciclado del sensor nuevamente hacia
la cámara, lo que implica que el aire no entra ni sale del sig
tema, Gnicamente se está reciclando internamente (Figura 2a).
Si la hoja aislada en la cámara está fotosintetizando,
entonces la concentración de C o p en el sistema tendrá un decremento, que continuará hasta que el punto de compensación‘
r
A
T
M
O
8
r
I
R
A
10
de COZ d e f o t o s í n t e s i s sea a l c a n z a d o ,
Por e l contrario, s i
l a p l a n t a u h o j a e s t á t r a n s p i r a n d o , l a c o n c e n t r a c i ó n d e VA a s
mentará progresivamente h a s t a provocar cierre estomatal o l a
saturación del aire interno.
t é t i c a para C O Z
La tasa de a s i m i l a c i ó n f o t o s i n -
( F C 0 2 ) p u e d e s e r c a l c u l a d a c o n la s i g u i e n t e
ecuación :
FC02=
'
t*A
'
donde:
A C a = Cambio d e c o n c e n t r a c i ó n d e C o p e n un i n
t e r v a l o de tiempo,
-
V = Volumen d e l sistema
(cámara d e a s i m i l a ción).
t = I n t e r v a l o de tiempo
e n que s e tomaron l o s
cambios en l a concent r a c i ó n d e COZ.
A = Area f o l i a r .
A s í p u e s , s e t i e n e q u e l a t r a n s p i r a c i ó n e s la p é r d i d a d e
agua d e l a s p l a n t a s en forma de v a p o r , donde:
Tasa t r a n s p i r a t o r i a = T r a n s p i r a c i ó n p o r u n i d a d d e t i e m p o y p o r
unidad de área f o l i a r .
P
F
AVA
AF
F = Flujo de aire.
AVA = D i f e r e n c i a d e c o n c e n
t r a c i ó n de
VA a n t e s
y d e s p u é s d e pasar
p o r l a cámara.
AF = A r e a f o l i a r .
A
11
Adicionalmente, debe mencionarse que tanto para fotoslfr
tesis como para transpiración los sistemas deben contar con
una fuente de luz de intensidad y calidad adecuadas, puesto
que los estomas generalmente se cierran en la obscuridad.
Sistema a b i e r t o .
En un sistema de este tipo, fluye aire a través de la c&
mara de asimilación donde se encuentra la planta con una concentración de
mados de
l a
COZ
y vapor de agua conocidos, generalmente to-
atmósfera.
El aire se hace circular por la cáma-
ra para posteriormente salir; el sensor medirá entonces, la
diferencia de concentración de C o p
o
de VA contenidos en mueg
tras de aire, antes y después de haber circulado por la cámara (Figura 2b), Long (1982).
--
.I*
12
1.2.
LA FOTOSINTESIS Y TRANSPIBBCION COHO PROCESOS DIFUSIVOS.
Por analogía con la Ley de Ohm, tanto fotosíntesis (Fs)
como transpiración (Tr) se pueden considerar como procesos directamente relacionados con los gradientes de concentración
del gas que difunde (GO2 o vapor de agua) entre la hoja y la
atmósfera, e inversamente proporcionales a la resistencia total que deben vencer para difundir.
Como ambos procesos ocu-
rren a través de los estomas, pueden visualizarse como sigue:
Durante la fotosíntesis, entra el C02 a la hoja a través
de los estomas debido a la existencia de un gradiente de difu-
sión entre las células del mesófilo de la hoja que están foto-
-
sintetizando y la atmósfera.
La tasa de fotosíntesis, conside
rada como un flujo de C o p , está dada por la magnitud del gradiente, y la resistencia total a la difusión del C o p a lo largo del gradiente.
El flujo de gases entre regiones de concentraciones diferentes, e s análogo al flujo de electricidad a través de un cog
ductor eléctrico.
Haciendo una analogía a la Ley de Ohm, se
tiene:
FC02 =
AC
Ir
donde:
FC02 =
bC
Tasa fotosintética.
= Gradiente de concentración de
COZ
Cr
=
entre la hoja y el aire.
Resistencia total de la hoja a
difusión de C 0 2
.
Modelo el8ctrico da la hoja quo fiwtro 01
FIGURA 3
el proceso dlfusivo del COO
Gaastra (1959) consideró que la vía de difusión para el
Cop entre la atmósfera y el punto de carboxilación consistía
de tres resistencias en serie:
la resistencia de l a capa
la resistencia estomatal (r S ) y la resistencia
frontera (r,),
del mesófilo (rm) (Figura 3 ) .
Por expansión de la ecuación
anterior:
-
FC02
-i
Ca
r
ra+rs+rm
,
donde
Ca = Concentración de COZ
en la atmósfera.
L a concentración d e C02 en el sitio de carboxilación es
desconocida, pero es asumida en el modelo de Gaastra como cero.
En modelos posteriores el punto de compensación de Cop
de fotoslntesis
(r)
ha sido considerado como una mejor esti-
ción de la concentración dentro d e la hoja.
.14
Similarmente, para tasa de t r a n s p i r a c i ó n ,
q u e es l a p é r
d i d a d e v a p o r d e a g u a d e l a h o j a a t r a v é s d e los e s t o m a s :
TT =
-
VAhoja
VAaire
r + r
a
S
Note que e l v a p o r d e agua p e r d i d o p o r t r a n s p i r a c i ó n es
e l evaporado en l a s s u p e r f i c i e s de c é l u l a s d e l m e s ó f i l o ,
por
l o q u e l a s r e s i s t e n c i a s a l a d i f u s i ó n s o n sólo l a s d e l e s t o m a
(r ) y d e l a capa f r o n t e r a (ra).
S
Naturaleza de las resistencias
Capa frontera
Cuando e v a p o r a una s u p e r f i c i e ( t a l como una h o j a ) ,
se
f o r m a una p e q u e ñ a c a p a d e m o l é c u l a s d e a i r e y d e v a p o r d e
agua a d y a c e n t e a e s t a s u p e r f i c i e ,
frontera.
l a c u a l s e c o n o c e como c a p a
La profundidad depende d e l a geometría de l a s u p e r
f i c i e , de l a v e l o c i d a d de evaporación y de l a v e l o c i d a d d e l
viento.
Cuando l a c a p a e s p r o f u n d a , e n una g r a n s u p e r f i c i e
o en a i r e e s t á t i c o ,
mayor
l a r e s i s t e n c i a a l a d i f u s i ó n d e gas es
Long (1982).
E l l o i m p l i c a que l a r e s i s t e n c i a d e capa f r o n t e r a (ra)
puede d i s m i n u i r s e m e d i a n t e el i n c r e m e n t o d e l f l u j o d e a i r e
s o b r e l a p l a n t a y p o r l a disminución del á r e a f o l i a r .
4
15
Los valores d e r
3 0 sm-l,
a
o s c i l a n n o r m a l m e n t e e n e l r a n g o 10 a
y p u e d e n s e r una f r a c c i ó n p e q u e ñ a o g r a n d e d e l a
resistencia total.
Estomática
L a o t r a r e s i s t e n c i a a l a c u a l se e n f r e n t a e l p r o c e s o d e
d i f u s i ó n d e l vapor está causada p o r e l g r a d o d e a p e r t u r a o
c i e r r e d e l o s estomas,
l o q u e r e p r e s e n t a una r e s i s t e n c i a v a -
riable.
Los p o r o s d e l o s e s t o m a s p u e d e n ser c o n s i d e r a d o s como
p u e r t o s de i n t e r c a m b i o e n t r e e l medio e x t e r n o y e l i n t e r i o r
de l a hoja;
por e l l o ,
l o s f a c t o r e s f í s i c o s que i n f l u y e n so-
b r e l a d i f u s i ó n d e v a p o r de agua a t r a v é s d e d i c h o s p o r o s
son importantes en e l e s t u d i o de l a t r a n s p i r a c i ó n
(1982).
Long
16
1.3
METODOS DE MEDICION DE COZ Y VAPOW DE AGUA
M e d i c i ó n d e l COZ
A n a l i z a d o r d e gases d e r a y o s i n f r a r r o j o s
(IRGA).
Principio
E l p r i n c i p i o e n e l q u e se b a s a n l o s a n a l i z a d o r e s d e
g a s e s d e r a y o s i n f r a r r o j o s y que a c o n t i n u a c i ó n se i n d i c a ,
e l que s e ñ a l a Long (1982):
es
E l a n á l i s i s de substancias en e l
-
e s p e c t r o d e l a r e g i ó n i n f r a r r o j a e s uno d e los m é t o d o s más c o
munes b a s a d o e n l a i n t e r a c c i ó n d e l a m a t e r i a y l a r a d i a c i ó n
electromagnética.
E s t a e s una r e l a c i ó n d i r e c t a e n t r e l a ab-
s o r c -i ó n d e l a s u b s t a n c i a e n e l e s p e c t r o i n f r a r r o j o y s u estructura molecular,
l a c u a l e s t á determinada por e l tiempo,
e l número y l a masa d e á t o m o s ,
l a s f u e r z a s mutuas d e f r o n t e -
r a y l a simetría de l a molécula (diferentes moléculas tienen
diferente espectro).
G a s e s y v a p o r e s q u e u s u a l m e n t e e x h i b e n e s p e c t r o s muy comp l e j o s son e s p e c i a l m e n t e adecuados para e l a n á l i s i s i n f r a r r o jo.
L a llamada r e g i ó n i n t e r m e d i a i n f r a r r o j a d e l e s p e c t r o ,
e n c u e n t r a e n t r e 2.5
se
y 2 5 um y e s u s a d a e n d i c h o a n á l i s i s .
La vibracíón y rotación d e l espectro de l a s moléculas,
c o n s i m i l i t u d e s y d i f e r e n c i a s e n t r e e l l a s p e r m i t i e n d o l a me-
17
diciÓn s e l e c t i v a de mezclas de gases,
gitud.
-
caen d e n t r o d e e s t a l o n
En p r e s i o n e s y t e m p e r a t u r a s n o r m a l e s ,
estos e s p e c t r o s
e s t á n c a r a c t e r i z a d o s p o r e s t r u c t u r a s muy f i n a s d e m o l é c u l a s
i n d i v i d u a l e s formando bandas d e a b s o r c i ó n con l í n e a s c a r a c t e rzaticas,
d e forma que son r e g i s t r a d a s p o r e s p e c t r o s c o p i o s de
r e s o l u c i ó n moderada,
l o q u e a s e g u r a una b u e n a s e l e c t i v i d a d e n
l a medición de mezclas.
HCN,
"3,
CS2,
L o s g a s e s C O Z , H 2 0 , C O , S 0 2 , NO,
N20,
CH4 y t o d o s l o s h i d r o c a r b o n o s a l t o s e s t á n e n t r e
l o s c o m p o n e n t e s más comunes c o n a b s o r c i ó n e n l a r e g i ó n i n f r a -
rroja.
Por o t r o lado,
i g u a l e s (02,
N2,
He,
m o l é c u l a s c o n s t i t u i d a s p o r d o s átomos
etc.)
y g a s e s q u e no e x h i b e n momento d i -
p o l a r , no absorben r a d i a c i ó n i n f r a r r o j a .
E l d i ó x i d o d e c a r b o n o e s uno d e l o s g a s e s c o n m a y o r i n t e n
sidad de absorción y por l o tanto,
p a r t i c u l a r m e n t e adecuado
p a r a l a d e t e r m i n a c i ó n d e c o n c e n t r a c i o n e s muy p e q u e ñ a s p o r anl i s i s infrarrojo.
L a b a n d a d e m a y o r a b s o r c i ó n d e l COZ e s e n
h = 4.25 pm c o n p i c o s s e c u n d a r i o s e n X = 2 . 6 6 ,
2.77
y 1 4 . 9 9 pm.
Es i m p o r t a n t e h a c e r n o t a r q u e e l Ú n i c o g a s p r e s e n t e normalment e e n e l a i r e c o n un e s p e c t r o d e a b s o r c i ó n q u e s e e x t i e n d e sob r e e l e s p e c t r o d e l C O 2 es e l v a p o r d e agua,
diación i n f r a r r o j a en l a región 2.7
pm.
que a b s o r b e r a -
E l v a p o r d e agua se
p r e s e n t a u s u a l m e n t e e n e l a i r e e n c o n c e n t r a c i o n e s mucho mayores que e l COZ.
significativo;
E s t a i n t e r f e r e n c i a r e p r e s e n t a un p r o b l e m a
s i n embargo,
s e puede v e n c e r h a c i e n d o e l s e c a -
do d e l a i r e que v a a s e r examinado o b i e n ,
-
filtrando l a radia
c i d n e n l a l o n g i t u d d e onda donde l a a b s o r c i ó n d e los d o s ga-
ses coincide.
Construcción
E l a n a l i z a d o r d e g a s e s d e r a y o s i n f r a r r o j o s con-
siste de t r e s partes básicas:
l a fuente de rayos i n f r a r r o j o s ,
l a s cámaras d e muestre0 y e l d e t e c t o r .
La Figura 4 i l u s t r a
l a c o n s t r u c c i ó n d e un I R G A c o n d o s c á m a r a s d e t e c t o r a s d e abs o r c i ó n en p a r a l e l o ;
e s t e e s e l t i p o d e c o n s t r u c c i ó n más c o -
múnmente u s a d o J a n a c
e t uk?. ( 1 9 7 1 ) l a d e s c r i b e n :
Dos e s p i r a l e s d e n i c r o m i o ( o uno c o n e l r a y o d i v i d i d o
p o r e s p e j o s ) c a l e n t a d o s p o r una c o r r i e n t e d e b a j o v o l t a j e a
una t e m p e r a t u r a d e 600-800°C ( r o j o v i v o ) ,
d e r a d i a c i ó n (1,2).
s i r v e como f u e n t e
L a r a d i a c i ó n d e un c a l e n t a d o r
a t r a v é s d e l tubo de muestra (4),
(2)
c o n t e n i e n d o e l a i r e que v a
a s e r a n a l i z a d o y e n t r a a una c á m a r a d e a b s o r c i ó n ( 6 ) .
d i a c i ó n d e l o t r o c a l e n t a d o r (1)
pasa
L a rg
p a s a a t r a v é s d e l t u b o d e re-
f e r e n c i a ( 3 ) , l l e n a d o con n i t r ó g e n o o con a i r e l i b r e de COZ y
H20 y e n t r a e n o t r a cámara ( 5 ) .
das d e l d e t e c t o r (7)
cidn de aluminio)
Las d o s cámaras e s t á n s e p a r a
p o r una membrana f i n a ( h e c h a
d e 5 a 1 0 pm d e e s p e s o r ,
c o n una a l e =
l a c u a l f o r m a uno
d e l o s e l e c t r o d o s d e l condensador d e l diafragma.
Las v f a s de
r a d i a c i ó n s o n i n t e r r u m p i d a s p o r . un o b t u r a d o r r o t a c i o n a l (10)
q u e t i e n e una f r e c u e n c i a c o n s t a n t e e n t r e 2 y 20 Hz, c a u s a n d o
cambios d e p r e s i ó n p e r í o d i c a en e l d e t e c t o q c o n v i b r a c i o n e s
s i m u l t á n e a m e n t e d e l a membrana.
19
a
n
FIGURA
an parotelo.
Im
8
Puontam da Radia&
4
.
-e>
20
La amplitud de l a v i b r a c i ó n está determinada por l a d i f e
r e n c i a d e p r e s i ó n e n t r e l a s d o s cámaras,
l a cual está deter-
minada p o r l a d i f e r e n c i a d e c o n c e n t r a c i ó n d e COZ e n t r e l o s t u bos de a n á l i s i s y de r e f e r e n c i a .
E l cambio en l a amplitud de
l a v i b r a c i ó n d e l a membrana p r o d u c e un c a m b i o e n l a c a p a c i d a d
d e l condensador e l c u a l e s i n v e r s a m e n t e p r o p o r c i o n a l a l cambio
de v o l t a j e a t r a v é s d e l condensador.
Calibración
Aunque l a c o n s t r u c c i ó n d e l IRGA d e s c r i t o t i e n e a l t a
s e n s i b i l i d a d y capacidad de monitoreo continuo de concentrac i ó n d e CO2,
c a r e c e d e e s t a b i l i d a d en su c a l i b r a c i ó n p o r l a r -
gos p e r í o d o s de tiempo.
Para cualquier trabajo e s esencial
calibrar e l analizador diariamente.
E l r e q u e r i m i e n t o mínimo
p a r a una b u e n a c a l i b r a c i ó n e s una f u e n t e d e g a s l i b r e d e C O Z
( g e n e r a l m e n t e Ne)
y una f u e n t e d e a i r e q u e c o n t e n g a una c o n
c e n t r a c i ó n c o n o c i d a d e C02 e n e l r a n g o a s e r a n a l i z a d o y c o g
t e n i d o p r e f e r i b l e m e n t e e n un c i l i n d r o d e a l u m i n i o ( é s t e no
d e b e a b s o r b e r C O Z e n s u s p a r e d e s como l o h a r í a un c i l i n d r o d e
acero).
1.
E x i s t e n d o s f o r m a s d e c a l i b r a r e l IRGA:
Calibración absoluta.
Cuando e l a n a l i z a d o r v a y a a s e r
usado p a r a d e t e r m i n a r l a c o n c e n t r a c i ó n e x a c t a d e CO2 en
una m u e s t r a d e a i r e ,
absoluto;
es d e c i r ,
b r e d e C02.
é s t e d e b e s e r c a l i b r a d o e n e l modo
l a m u e s t r a es c o m p a r a d a c o n g a s li-
Para dicha calibración,
e l g a s l i b r e d e C02
21
es pasado a través de ambos tubos, (el de referencia y
el de análisis), haciendo el ajuste del cero en el galvanómetro.
Posteriormente, muestras de aire con conceo
tración de COZ conocidas también se pasan a través de
ambos tubos y la deflexión de la aguja en el galvanómetro deberá ajustarse con la ganancia de amplificación.
2.
Calibración diferencial.
Cuando el analizador vaya a
ser usado para determinar un cambio en la concentración
de C02; por ejemplo, la diferencia de concentración de
COZ en una corriente de aire antes y después de haber
pasado sobre una hoja, el analizador deberá ser calibra
do en modo diferencial.
En este modo es posible detec-
tar cambios muy pequeños de concentración de C02 (por d e
~ algunos modelos).
-bajo de 100 ~ g m -con
Para una Cali-
bración precisa se requiere que los tubos de análisis y
referencia sean llenados con un mismo aire de una conce2
tración conocida de COZ; el cero es entonces ajustado en
el galvanómetro
Long (1982).
Posteriormente se hace pasar un flujo igual de aire pero
con mayor concentración (conocida también) de C02 por el
tubo de referencia, al mismo tiempo que el otro gas de
menor concentración de C O Z pasa por el tubo de análisis;
en estas condiciones se ajusta la ganancia deseada en el
galvanómetro.
Este tipo de calibración permite versati-
lidad en la precisión de la calibración.
22
M e d i c i ó n d e l v a p o r d e agua
L o s c o n c e p t o s s o b r e l a s c a r a c t e r í s t i c a s f í s i c a s d e l vap o r d e agua que s e i n d i c a n a c o n t i n u a c i ó n ,
s o n l o s que s e ñ a l a
Ludlow (1982) :
F í s i c a d e l v a p o r d e agua.
E l v a p o r d e a g u a e s un g a s q u e e j e r c e una p r e s i ó n p a r c i a l en e l a i r e .
Esta presión en a i r e saturado (Presión de
vapor saturada),
e x p r e s a d a e n k i l o p a s c a l e s (1 KPa = 75 mmHg
a 0°C = 1 0 mbar)
se i n c r e m e n t a c o n l a temperatura.
bargo,
S i n em-
e l a i r e generalmente no está saturado y l a p r e s i ó n de
v a p o r es menor q u e l a p r e s i ó n d e v a p o r s a t u r a d o .
Temperatura de punto d e r o c í o
Es l a t e m p e r a t u r a a l a c u a l l a p r e s i ó n d e v a p o r i g u a l a
l a presión de vapor saturada,
s i e l a i r e es e n f r i a d o s i n ga-
n a r o p e r d e r agua.
Deficit de saturación
Es l a d i f e r e n c i a e n t r e l a p r e s Ón d e v a p o r y l a p r e s i ó n
de vapor saturada a l a temperatura d e l a i r e .
bras,
En o t r a s p a l a -
e l d é f i c i t d e s a t u r a c i ó n es un í n d i c e d e l p o d e r d e se-
cado d e l a i r e ;
sa de evaporación.
es l a misma,
-
e n t r e mas a l t o e l d é f i c i t más g r a n d e es l a t a
Si l a temperatura d e l a i r e y de l a h o j a
e l d é f i c i t d e s a t u r a c i ó n es e q u i v a l e n t e a l a d i -
-
4
23
ferencia de presiones de vapor de aire y de la hoja (e -e
h a
y está directamente relacionado con la tasa de transpiración
TT :
TT =
eh - e
a
r + r
a
s
,
donde
r
a y rs = son respectivamente
la resistencia de la
capa frontera y la
resistencia estomatal a la transferencia de vapor de agua.
Humedad relativa
Es la razón de la'presión de vapor y la presión de vapor
saturada a la temperatura del aire (e/eo) y se expresa como
un porcentaje.
La humedad relativa se usa principalmente p a
ra describir el contenido de humedad en el aire, y como no
tiene influencia directa en ningún proceso biológico,es preferible que en su lugar se usen uno
metros descritos anteriormente.
o
mls de los otros pará-
Un error comGn en estudios
de ambiente controlado es el de mantener constante la humedad
relativa con el fin de mantener constante la tasa de evaporación mientras se varía la temperatura experimentalmente.
Es-
to da como resultado un déficit de saturación, y por lo tanto
la tasa de evaporacibn se incrementa con la temperatura.
Todos estos parámetros, que describen el contenido de
vapor de agua en el aire, están estrechamente interrelaciona
dos, de tal forma que si se conoce la temperatura del aire
(del bulbo seco) pueden conocerse cualquiera de ellos. Estas
24
interrelaciones se muestran en la carta psicrométrica de la
Figura 5; por ejemplo, si las temperaturas de bulbo húmedo
y seco son 1 0 y 2 0 ° C respectivamente, la humedad relativa
es 5 0 % , la tasa de humedad es 7 . 5
g
agua kg-I y la presión
de vapor es 8.5 mmHg.
Sensores d e humedad
Los sensores de humedad trabajan sobre uno de tres pri;
cipios: de presión de bulbo húmedo, humedad relativa
o
tempe
-
ratura de punto de rocío.
Psicrometrfa d e b u l b o húmedo y seco.
- Un psicrómetro de este tipo consiste de d o s sensores de
temperatura, uno de los cuales está cubierto con muselina que
se humedece.
La evaporación enfría el sensor humedecido a la
temperatura de bulbo húmedo.
La presión de vapor de agua (e)
es calculada por la siguiente fórmula:
donde T 1 y T son, respectivamente, las temperaturas de bulbo
húmedo y seco; e
S
(TI) es la presión de vapor saturada a la
temperatura de bulbo húmedo, y y es la constante psicrométrica, valor del cual depende que elpsicrómetro sea ventilado
no.
Los valores obtenidos con psicrómetros ventilados son
o
4
25
+amporo+uro
do
bulbo
8080
PC)
-
Carta PaIcromÓtrica iiustrarndo las rela
cionea entre tempuaturu da bulbo seco y tuno
peratura de bulbo húmedo, hummdod r e l a t i
vo ( RH l. rozón de humedad y- prm8iÓn d e vo-
-
por.
*
26
g e n e r a l m e n t e más p r e c i s o s q u e c o n l o s d e l t i p o n o v e n t i l a d o s .
L o s p s i c r ó m e t r o s d e b u l b o húmedo y s e c o s o n r e l a t i v a m e n t e b a -
ratos y simples.
S e n s o r e s d e humedad r e l a t i v a .
E s t o s v a r í a n d e s d e l o s s i m p l e s d i s p o s i t i v o s d o n d e l a humedad r e l a t i v a i n f l u y e e n l a s p r o p i e d a d e s m e c á n i c a s d e l m a t e r i a l , h a s t a l o s más c o m p l e j o s d o n d e l a humedad a f e c t a l a s p r o
-
piedades e l é c t r i c a s de l o s sensores.
E l s e n s o r d e c l o r u r o d e l i t i o es e l t i p o más común d e
s e n s o r e l é c t r i c o y es r e l a t i v a m e n t e b a r a t o .
E l cloruro de
l i t i o e s h i g r o s c ó p i c o y e l c o n t e n i d o d e humedad d e l a i r e d e t e r m i n a cuanta agua a b s o r b e ,
c i a AC d e l s e n s o r .
l o c u a l i n f l u y e en l a r e s i s t e n -
E s t e t i p o d e s e n s o r es s e n s i b l e a c o n t a -
minación por polvo y o t r a s p a r t í c u l a s higroscópicas.
Todos
l o s s e n s o r e s e l é c t r i c o s s o n s e n s i b l e s a ' c a m b i o s e n l a temperatura,
p o r l o c u a l d e b e h a c e r s e una c o r r e c c i ó n y a s e a e l é c -
tricamente o por cálculo.
Otro método s i m p l e y b a r a t o está basado en e l c o l o r d e l
c l o r u r o d e c o b a l t o impregnado en p a p e l ,
e l c u a l cambia a a z u l
p a r a humedad r e l a t i v a b a j a y d e l i l a a r o s a p a r a humedad r e l a
tiva alta.
E s t o s i n d i c a d o r e s son u s a d o s c o m e r c i a l m e n t e p a r a
c u b r i r v a r i a c i o n e s d e l 10 a l 1 0 0 % d e humedad r e l a t i v a .
J
27
Higrometría de punto d e rocío.
Existen básicamente dos tipos de sensores de punto de
rocío:
de sal saturada e higrométro de condensación.
Los del tipo de sal saturada son ampliamente usados por
su bajo costo y simplicidad; además de no ser afectados por
iones contaminantes.
Su mayor limitación es una baja respues
ta en tiempo e incapacidad de medir humedad relativa menor a
10%.
Los del tipo de condensación operan en una amplia gama
de puntos de rocío y son más rspídos, precisos y confiables,
por lo que son más costosos y complejos.
El aire que va a ser medido, se circula a través del apa
rato, el cual lo enfría hasta que el rocío empieza a tomar
forma; este es detectado Óptica
o
eléctricamente, haciendo ce
-
sar el enfriamiento; cuando el rocío se está evaporando, el
enfriamiento recomíenza.
El equilibrio de temperatura a la
cual justamente el rocío se está formando y evaporando es la
temperatura de punto de rocío, y es a esta temperatura a la
cual el sistema deberá estar calibrado antes de iniciar las
mediciones.
28
XI. DISEBO E IMPLEHENTACION DEL S I S T E M A DE M E D I C I O N DE G A S E S
C a r a c t e r í s t i c a s d e l sistema
L a c o n f i g u r a c i ó n usada p a r a e s t e p r o y e c t o fue l a d e l s i c
tema a b i e r t o ;
en e l cual,
como y a s e d e s c r i b i ó ,
se s u m i n i s t r a
a i r e d e l a a t m ó s f e r a c o n c o n c e n t r a c i ó n d e C02 y v a p o r d e a g u a
conocidas,
a t r a v é s d e una c á m a r a d e a s i m i l a c i ó n d o n d e s e en-
cuentra e l material v e g e t a l .
diseño fueron:
Los sensores u t i l i z a d o s en este
un a n a l i z a d o r d e g a s e s d e r a y o s i n f r a r r o j o s p a
r a e l C O Z y un h i g r ó m e t r o d e p u n t o d e r o c í o d e l t i p o c o n d e n s a c i ó n p a r a e l v a p o r de agua.
L o s s i s t e m a s a b i e r t o s p u e d e n ser d i s e ñ a d o s e n d i v e r s o s
tamaños,
como e l d e B e a d l e
uno p a r a h o j a s s o l a s .
e t al. ( 1 9 7 4 )
quienes diseñaron
E s t o s a u t o r e s t a m b i é n a f i r m a n que l o s
h i g r ó m e t r o s de punto d e r o c í o s o n i n s t r u m e n t o s p r e c i s o s y
c o n f i a b l e s para medir f l u j o s de gases.
Determinación d e l a tasa f o t o s i n t é t i c a
(FC02)
A l m e d i r FC02 una m u e s t r a d e l a i r e q u e e n t r a a l a cámar a pasa a t r a v é s d e l tubo d e r e f e r e n c i a y o t r a muestra d e l
a i r e que s a l e d e l a cámara es p a s a d o a t r a v é s d e l t u b o d e
análisis.
tenído.de
E l I R G A m o n i t o r e a e n t o n c e s l a d i f e r e n c i a d e l conCOZ e n e l a i r e a n t e s y
l a cámara d e a s i m i l a c i ó n .
después d e haber entrado a
29
Para calcular la tasa fotosintética FC02 se tiene la siguiente relación:
FC02 = F hCa
A
donde:
F = flujo del aire a través
de la cámara.
ACa
=
diferencia de concentración de C 0 2 antes y después de pasar por la cámara.
A = Area foliar.
Para determinar FC02 en un sistema abierto los requerimientos son: que el IRGA pueda ser calibrado en modo diferen
cial; que el flujo del aire a través de la cámara sea constan
te y conocido en forma precisa y que el área foliar sea determinada también en forma precisa.
L a s ventajas en el uso de un sistema abierto son:
1.
Se puede determinar simultáneamente la concentración
de C02 en un número n de cámaras de asimilación, mediante el uso de un interruptor.
2.
Mediante el acoplamiento de otros instrumentos, es
posible medir otros procesos en forma simultánea,
como la transpiración.
30
D e t e r m i n a c i a n d e l a t a s a t r a n s p i r a t o r i a (TT)
Con e l s i s t e m a d e s c r i t o a n t e r i o r m e n t e e s p o s i b l e c a l c u l a r también l a t a s a de t r a n s p i r a c i ó n d e l a s p l a n t a s .
Así,
temperatura o b t e n i d a con e l h í g r ó m e t r o d e punto d e r o c í o ,
t o a l a e n t r a d a como a l a s a l i d a d e l a c á m a r a ,
marse a densidad d e v a p o r d e agua,
v a p o r d e a g u a (CVA)
es d e c i r ,
la
tag
debe t r a n s f o r -
concentración de
u t i l i z a n d o l a s T a b l a s M e t e o r o l ó g i c a s Smith-
s o n i a n a s ( T a b l a s No.
108) A n e x o 1.
Una v e z o b t e n i d o s e s t o s
d a t o s se c a l c u l a en forma d i r e c t a l a t a s a t r a n s p i r a t o r i a :
F l u j o x AVA
TT = Area f o l i a r
donde
AVA =
CVA s a l i d a CVA e n t r a d a
Descripción d e l sistema
A c o n t i n u a c i ó n s e p r e s e n t a e l diagrama d e b l o q u e s (Figur a 6),
e n e l c u a l se m u e s t r a n e n f o r m a e s q u e m á t i c a a t o d o s
los c o n s t i t u y e n t e s d e l s i s t e m a , a s í como l a s r e l a c i o n e s ent r e e l l o s y e l f l u j o que e l p r o c e s o d e m e d i c i ó n d e g a s e s
tie
n e e n e l mismo.
Sensores d e C O Z y v a p o r d e a g u a .
Sensor d e C02
Se p r e t e n d . i Ó u t i l i z a r un a n a l i z a d o r d e g a s e s d e r a y o s
infrarrojos
(IRGA) m a r c a Beckman M o d e l o 8 6 5 ( A n e x o 21, e l
31
ISTLMA
ATMO8tLRA
DL
O821 55
D
I
A
G
R
A
M
A
A -
ROTAMETRO
f
DE
ASIMILACION
n
HIOROMETRO
D E
R
PUNTO
G
D E ROCIO
A
B*
L
O
E
S
T
R
.
Q
U
E
S
I
.a
R O>
TAMETRO
(
i
(AMslENTe)
FIGURA 6
:
n
i
4
32
cual determina continuamente la concentración de C O Z en una
mezcla de gases.
El análisis está basado en una medición
diferencial de la absorción de energía infrarroja.
Para convertir las lecturas en valores de concentración,
es necesario utilizar una curva de calibración, elaborada en
el mismo instrumento y por investigador en función de los objetivos del experimento con base en gases de concentración conocida de C o p con precisión.
Sensor de humedad
Se utilizó un higrómetro de punto de rocko del tipo condensación, con detector Óptico, marca EGG Environmental
Equipment
Modelo 660 (Anexo 3 ) , cuyo sensor consiste de un
espejo capaz de detectar temperaturas de punto de rocío en el
rango - 4 0 ° C a +lOO°C.
Similarmente, como en el caso de las concentraciones de
C o p , las temperaturas obtenidas deben transformarse a vapor
de agua, es decir, concentración de vapor de agua (CVA),
y
una vez obtenidos estos datos, se calcula en forma directa la
tasa transpiratoria.
Sistema de muestre0 del g a s .
Para este sistema s e utilizaron básicamente tres elementos: bombas de presibn-vacío, flujómetros y tubería.
33
I
L a s bombas d e v a c í o f u e r o n F E L I S A M o d e l o s FE 1 5 0 0 ( c a p a c i d a d 50 l / m i n )
y FE 1 6 0 0 ( c a p a c i d a d 80 i / m i n ) ,
modelo (Anexo 4 ) .
dos de cada
L a s d e mayor c a p a c i d a d se e m p l e a r o n p a r a
suministrar e l a i r e de l a atmósfera hacia e l sistema y l a s
d e menor p a r a m u e s t r e a r e l a i r e d e l a cámara q u e s e r í a a n a l &
z a d o p o r e l IRGA o s e n s o r d e VA a una t a s a d e 1 l / m i n p a r a e l
p r i m e r o , y d e 1.8 l / m i n para e l segundo s e n s o r .
L o s rotámetros u t i l i z a d o s ,
d e marca Dwyer, t a m b i é n fuel / m i n ) y s e r i e VFB
r o n d e d o s c a p a c i d a d e s : s e r i e RMC (30-300
(0-10
i/min)
(Anexo 5) para m o n i t o r e a r e l f l u j o s u m i n i s t r a d o
d e l a a t m ó s f e r a y e l m u e s t r e a d o d e l a cámara,
En r e l a c i ó n a l a t u b e r í a ,
(material
se u t i l i z ó :
respectivamente.
tubería de cobre
i m p e r m e a b l e a l C o p ) y t u b e r í a f l e x i b l e (manguera)
d e d i v e r s o s tamaños d e p e n d i e n d o d e l a n e c e s i d a d d e l f l u j o d e
aire.
Sistema d e acondicionamiento d e l a i r e .
E s t e s i s t e m a c o n s i s t i ó d e un c i l i n d r o d e m e t a l c o n c a p a
c i d a d d e 200 I t , a l c u a l s e l e i n s e r t a r o n e n l a t a p a s u p e r i o r
4 t u b o s d e 1 . 5 cm d e d i á m e t r o ; d o s d e e l l o s e r a n p a r a e l i n greso d e l a i r e de l a atmósfera hacia e l i n t e r i o r d e l c i l i n d r o
c o n e l o b j e t o d e h o m o g e n e i z a r l o , y l o s o t r o s t r e s e r a n salidas,
d o s d e l o s c u a l e s s e c o n e c t a r o n d i r e c t a m e n t e a l a cámara
y a l s e n s o r d e C o p o d e VA
(IRGA o HPR)
ner l a referencia d e l a i r e atmosférico.
con e l o b j e t o d e te-
34
Cámara de a s i m i l a c i ó n .
P a r a e l d i s e ñ o d e l a cámara d e a s i m i l a c i ó n , se tomaron
en cuenta básicamente tres a s p e c t o s : m a t e r i a l ,
tamaño d e l a
muestra a i n t r o d u c i r y c i r c u l a c i ó n d e l a i r e .
Dado q u e l o s e l e m e n t o s a a n a l i z a r s e e r a n e l C 0 2 y e l VA,
e l m a t e r i a l d e b l a ser impermeable a e l l o s ,
p o r l o que se u t i -
t r a n s p a r e n t e d e 5 mm d e e s p e s o r ,
l i z ó acr'ilico
u n i d o s c o n pe-
g a c r i l y s e l l a d o s con s i l i c ó n .
L a cámara s e d i s e ñ ó e n p r i n c i p i o p a r a p l a n t a s d e m a í z y
s o r g o d e s d e a p r o x i m a d a m e n t e 4 a 8 semanas d e e d a d .
mismo,
Por l o
s e c o n s i d e r ó l a a l t u r a y nGmero d e h o j a s c o m p l e t a m e n -
t e d- e s a r r o l l a d a s d e m a t e r i a l e s d e e s t a e d a d .
Así,
l a cámara
d e b e r í a ser d e l a s s i g u i e n t e s d i m e n s i o n e s aproximadamente
7 0 x 7 0 ~ 2 0cm ( F i g u r a
Además,
7).
como e n e s t o s e s t u d i o s e s n e c e s a r i o g a r a n t i z a r
e l c o n t a c t o uniforme y constante d e l a i r e con l a s u p e r f i c i e
foliar,
s e d e b í a p r o c u r a r una b u e n a c i r c u l a c i ó n d e l a i r e d e 2
t r o d e l a cámara; con t a l o b j e t i v o ,
á n g u l o s d e 90"
s e c o n s i d e r ó e l i m i n a r los
e n l a p a r t e s u p e r i o r d e l a misma,
c i d n d e un v e n t i l a d o r (marca SF, M o d e l o CK-120,
l a instala-
178 m3/hora)
en l a p a r t e i n f e r i o r para impulsar l a c o r r i e n t e d e a i r e que
ingresaba,
y t e n e r una s a l i d a d e a i r e d e l a c á m a r a d e l d o b l e
d i á m e t r o que l a d e l i n g r e s o .
35
CAMARA
DE
ASIMILACION
vol (opro%j
S S t . 6 Ita.
FtGURA 7
111.
PRUEBA DEL SISTEMA
La prueba del sistema se llevó a cabo para el proceso de
transpiración, mediante tres mediciones: de una planta de maíz,
de una de cártamo y una sin planta.
Esta Última sirvió para
detectar posibles fugas as€ como para estimar la precisión del
sistema
.
Se colocó la muestra en la cámara de asimilación y hacieg
do circular por ésta un determinado flujo de aire, se cuantificó la temperatura de punto de rocío del aire que entró y salió a través de la cámara, mediante el empleo del higrómetro
de punto de rocío.
-
Estas temperaturas se transformaron a concentraciones de
vapor de agua ( C V A )
utilizando las tablas meteorológicas Smith
sonianas (Tabla No. lo$),
para finalmente calcular en forma
directa la tasa transpiratoria (TT):
flujo
TT = AVA
Area foliar
donde,
CVA salida= CVA entrada.
Evaluación d e la cámara sin planta
Para esta primera prueba se tomaron 15 lecturas (Cuadro 1)
a un flujo de aire constante d e 7 8 . 2 l/min, obteniéndose los
resultados que se presentan en el Cuadro 2 .
C u a d r o 1.
Mediciones
Temperatura
Entrada
Salida
("CI
("C
1
hechas a l a c á m a r a d e a s i m i l a c i ó n s i n planta.
Concentración de vapor de agua
Salida
ACVA
Entrada
(9
m-7
Flujo:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
7.1
7.0
7.0
6.9
6.9
7.1
7.2
7 .O
7.1
7.0
7.0
7.0
7.0
6.9
6.9
7.1
7.1
7 .O
7.0
7.1
7.2
7.2
7 .O
7.1
7 .O
7 .O
7 .O
7 .O
6.9
6.9
7.801
7.750
7.750
7.699
7.699
7.801
7.851
7.750
7.801
7.750
7.750
7.750
-7.750
7.699
7.699
(h-9
(9i
-
.
,
'Tl-11
()lg an-2s-1)
1
78.2 l/min
7.801
7.801
7.750
7.750
7.801
7.851
7.851
7.750
7.801
7.750
7.750
7.750
7.750
7.699
7.699
o. o51
0.051
0.102
0.050
-
O
O
O
O
O
D
O
o
.
O
-0
O
O
.
38
Cuadro 2 .
E v a l u a c i ó n d e l a cámara s i n p l a n t a .
(LPM)
CVA (entrada)
gm-3
CVA ( s a l i d a )
-3
gm
78.2
7.753
7.770
Flujo
f
0.045
f
0.046
CVA
0.017
f
0.03
-.
Como s e p u e d e o b s e r v a r , l a d i f e r e n c i a
de concentra-
c i d n d e v a p o r e n t r e l a e n t r a d a y s a l i d a f u e mucho menor que l a
d e s v i a c i ó n e s t á n d a r d d e l a s mismas,
l o que i m p l i c a que e l
e r r o r d e d i s e ñ o o c o n s t r u c c i ó n de l a cámara e s menor a l e r r o r
e x p e r i m e n t a l y p o r t a n t o s e p u e d e c o n s i d e r a r como una cámara
e f i c i e n t e y p r e c i s a en c u a n t o a f u g a s d e l s i s t e m a .
dos p o s i b l e s f u e n t e s de e r r o r ,
De e s t a s
s e c o n s i d e r a que l a c o n s t r u c -
c i d n e s p r á c t i c a m e n t e l a d e mayor i n f l u e n c i a .
M e d i c i o n e s h e c h a s en p l a n t ; a a . d e ma42 y . c b r t a m o - - - -
En e s t a s d o s p r u e b a s s e tomaron 1 0 l e c t u r a s p a r a t r e s
flujos distintos
(Cuadros
3 y 4 ) con l a s c u a l e s s e c a l c u l a r o n
l a s t a s a s t r a n s p i r a t o r i a s a d i f e r e n t e s f l u j o s que s e p r e s e n t a n
en e l C u a d r o 5 y s e i l u s t r a n g r á f i c a m e n t e en l a F i g u r a 8 .
Se p u e d e n o t a r que e l s i s t e m a e s s u f i c i e n t e m e n t e s e n s i b l e p a r a d i f e r e n c i a r t a s a s d e t r a n s p i r a c i ó n b a j a s como l a d e l
maíz y más e l e v a d a s como l a d e c á r t a m o y aún m á s i m p o r t a n t e
s e puede a p r e c i a r que l a t a s a t r a n s p i r a t o r i a (TT) en ambas
p l a n t a s tuvo cambios s i g n i f i c a t i v o s conforme s e v a r i ó e l f l u -
_-
,
39
Mediaianes .hechas a una p l a n t a d e m a í z .
C u a d r o 3.
A r e a Foliar:
1 5 6 5 em2.
Temperatura
Entrada
Sal ida
("C
1
("C)
Entrada
(9m-
Concentración de vapor de agua
ACVA
Salida
(sm- 9
(h3'
,
Flujo: 118.2 l / m i n
1
2
3
4
5
6
7
8
9
10
6.3
6.3
6.6
7.1
7.0
7.0
6.4
6.7
6.4
5.8
7.2
7.2
7.3
7.7
7.4
7.7
6.4
7.3
6.9
6.7
7.404
7.404
7.550
7.801
7.750
7.750
7.452
7.600
7.452
7.165
7.851
7.851
7.902
8.110
7.954
8.110
7.699
7.902
7.699
7.600
0.447
0.447
0.352
O. 309
O. 204
O. 360
O. 247
0.302
O. 247
0.435
O. 563
O. 563
0.445
O .389
0.257
O .453
0.31 1
O. 380
0.311
O. 547
O. 305
O. 253
0.354
O. 302
0.302
0.402
0.453.
0.354.
o.354
0.354
O. 254
0.211
O. 235
O. 251
O. 251
O. 334
O. 377
O. 295
O. 295
O. 295
0.36
0.621
0.514
O. 357
0.413
O. 621
O. 567
0.517
O. 464
0.517
O. 204
0.352
O. 291
o. 202
O. 234
0.352
0.321
O. 293
O. 267
O. 293
Flujo: 78.2 i / m i n
1
2
3
4
5
6
7
8
9
10
6.8
6.8
6.7
6.7
6.7
6.5
6.5
6.7
6.7
6.7
7.4
7.3
7.4
7.3
7.3
7.3
7.4
7.4
7.4
7.4
7.649
7.649
7.600
7.600
7.600
7.501
7.501
7.600
7.600
7.600
7.954
7.902
7.954
7.902
7.902
7.902
7.954
7.954
7.954
7.954
.
Flujo: 53.2 l/min
1
2
3
4
5
6
7
8
9
10
7 .O
6.8
6.8
6.9
7.0
6.8
6.8
6.9
6.9
6.9
7.7
8.0
7.8
7.5
7.8
8.0
7.9
7.9
7.8
7.9
7.75
7.649
7.649
7.699
7.75
7.649
7.649
7.699
7.699
7.699
8.11
8.27
8.163
8.006
8.163
8.27
8.216
8.216
8.163
8.216
40
2uadro 4 .
M e d i c i o n e s h e c h a s a una p l a n t a d e c á r t a m o .
Temperatura
Entrada
Salida
("C)
("C)
Entrada
(9m-
3,
Area F o l i a r :
1181 c m 2
Concentraci6n de vapor de agua
1qq-t'
Salida
ACVA
(b
(9m(yg cm-'s-')
F l u j o : 118.2 l/min
1
2
3
4
5
6
7
8
9
10
7 .O
7.2
7.2
7.2
7.3
7.3
7.0
7.1
7.3
7.1
10.6
1 1 .o
1o.a
10.9
10.6
10.7
10.5
10.5
9.8
9.9
7.750
7.801
7.851
7.851
7.902
7.902
7.750
7.801
7.902
7 .SO1
9.763
10.01
9.887
4.949
9.763
9.825
9.702
9.702
9.280
9.339
2.013
2.204
2.036
2.098
1.861
1.923
1.952
1 .go1
1.378
1.538
3.36
3.68
3.40
3.50
3.10
3.21
3.26
3.17
2.30
2.56
1.378
1.548
1.557
1.608
1.668
1.640
1.690
1.690
2.053
1.76
1.48
1.66
1.67
1.73
1.79
1.76
1.82
1.82
2.19
1.89
2.390
2.501
2.580
2.710
2.580
2.549
2.789
2.831
2.840
2.941
1.79
1.88
1.94
2.03
1.94
1.91
2.10
2.13
2.13
2.21
F l u j o : 76.2 i/min
1
2
3
4
5
6
7
8
9
10
7.3
7.2
7.3
7.2
7.2
6.96.8
6.8
6.8
6.9
9.8
10.0
10.1
10.1
10.2
9.9
Y .9
9.9
10.5
10.1
7.902
7.851
7.902
7.851
7.851
7.699
7.649
7.649
7.649
7.699
9.280
9.399
9.459
9.459
9.519
9.339
9.339
9.339
9.702
9.459
Flujo: 53.2 l / m i n
1
2
3
4
5
6
7
8
9
10
7 .O
6.9
7.0
7.0
7 .O
7.2
7.1
6.9
7 .O
6.8
11.2
11.3
11.5
11.7
tl.5
11.6
11.9
11.8
11.9
11.9
7.750
7.699
7.750
7.750
7.750
7.851
7.801
7.699
7.750
7.649
10.14
10.20
10.33
10.46
10.33
10.40
10.59
10.53
10.59
10.59
Cuadro 5.
F l u j o (LPM)
Tasas t r a n s p i r a t o r i a s (TT) promedio a d i s t i n t o s
f l u j o s d e a i r e a t r a v é s d e l a cámara d e a s i m i l a c i ó n e n una p l a n t a d e m a í z y c á r t a m o .
CVA ( e n t r a d a )
gm -3
TT
l.ig cm - 2 s - 1
Rango
C A R T A M O
53.2
7.7420.05
2.0020.13
1.87-2.13
76.2
7.7720.11
1.7820. 18
1.60 1.96
118.2
7.8320.59
3.1520.42
2.73
3.57
M A 1 2
53.2
7.6920 .O4
O . 2820.05
O . 23-0.33
76.2
7.5920.05
O . 2820.05
O . 23-0.33
118.2
7 .5320.20
O .42+0.11
O . 31-0.53
j o de aire,
l o c u a l p u d i e r a d e b e r s e a l a s v a r i a c i o n e s en l a
r e s i s t e n c i a d e l a c a p a f r o n t e r a a s o c i a d a s c o n l o s aumentos
d e l f l u j o de a i r e ,
y a que n o se d e t e c t a r o n c a m b i o s e n l a con-
c e n t r a c i ó n d e v a p o r d e agua en e l a i r e c i r c u l a n t e .
G o n z á l e z (1982)
e m p l e a n d o una c á m a r a d e f l u j o a b i e r t o
p a r a p l a n t a s c o m p l e t a s d e 200 dm3 d e c a p a c i d a d y un h i g r ó m e t r o d e p u n t o d e r o c í o como s e n s o r d e humedad,
d e t r a n s p i r a c i ó n d e 0.9
g o a 3OoC y 800 pEm-2s'1.
a 1.3 p g cm-2s'1
encontró tasas
para plantas de sor-
Las d i f e r e n c i a s c o n l a s d e l p r e -
s e n t e t r a b a j o pueden d e b e r s e a l a e s p e c i e ,
a l a temperatura
y sobre todo a l a radiación fotosintéticamente activa.
I
42
1.0
F I G U R A 8 . T a s o Trancrpiratorio (TT)
de aire a través de
a di8tintOS
flujos
la cámara
de asimilación
en uno planta
de m a k y córtame.
&
I Z T A P A L A P ~ '
&RVlCiQ QOCUMENiALQ
J
43
Con una c á m a r a d e 760 dm
de capacidad recubierta de
l i e t i l e n o y p a r a f i l m L i v e r a (1985)
plantas completas de sorgo,
0.09
pg c m - l C 2 e n
PO-
midió transpiración de
encontrando v a l o r e s de 0.01 a
donde e l á r e a c o r r e s p o n d e a l s u e l o donde
estaban l a s plantas.
A c e r c a d e e s t a t é c n i c a c o n c l u y e que,
d e s s i b i e n pueden r e p r o d u c i r r
te natural,
ción,
r
S ,
a
e s t a s cámaras g r a n
d i s t i n t a s a l a s d e l ambien-
dan r e s u l t a d o s e x c e l e n t e s p a r a m e d i r t r a n s p i r a -
f o t o s í n t e s i s y r e s p i r a c i ó n d e l o s c u l t i v o s en e l
campo; a g r e g a q u e e s t a t é c n i c a d e b e s e r Ú t i l p a r a g e n o t i p o s
a d i f e r e n t e s n i v e l e s d e agua y temperatura.
Por o t r o lado,
c o n una c á m a r a d e a s i m i l a c i ó n d e 1 dm
a p l i i a d a en h o j a s s o l a s ,
e s t e mismo a u t o r d e t e c t ó d i f e r e n c i a s
s i g n i f i c a t i v a s e n t r e g e n o t i p o s d e s o r g o y m a í z p a r a T T que
v a r i a r o n d e 0.06
rencias en r
S
a 0 . 1 0 v g cm'1s'2,
d e 2.4
a 4.3
asimismo e n c o n t r ó d i f e -
s cm-l.
E v a l u a c i ó n e x p e r i m e n t a l d e la r e s i s t e n c i a d e c a p a f r o n t e r a ( r a )
Considerando que l a s v a r i a c i o n e s o b t e n i d a s en l a t a s a d e
t r a n s p i r a c i ó n d e l a s p l a n t a s d e maíz y cártamo pudieron deber-
se a l a d i s m i n u c i ó n d e l a r e s i s t e n c i a d e c a p a f r o n t e r a p o r e l
h e c h o d e h a b e r v a r i a d o l o s f l u j o s d e l a i r e a t r a v é s d e l a cá-
-
mara d e a s i m i l a c i ó n , s e p r o c e d i ó a e v a l u a r e n f o r m a e x p e r i m e n
t a l esta resistencia.
44
Con un slmil de cada planta de área conocida, hechos a
-
base de papel filtro humedecido, se procedió de la misma for
ma que con las plantas naturales; se introdujo en la cámara,
se circuló aire con distintos flujos
a
través de ésta y se
tomaron lecturas de temperatura de punto de rocío en la entrada y salida (Cuadros 6 y 7 ) .
Con el uso de papel filtro humedecido s e elimina la rs
(la resistencia estomatal) y se logra una tasa de evaporación
(TE), de tal forma que a partir de la ecuación para calcular
transpiración como proceso difusivo, se pudiera calcular la
r
a
de la cámara diseñada:
TE5r
si r
S
=
O, entonces
TE =
Y ra
=
a
AVA
+ r
6
AVA
ra
AVA
TE
Note que AVA corresponde al gradiente de concentración
de vapor de agua entre la salida y entrada de la cámara de
asimilación al medirse el símil de papel filtro, y que TE
-
equivale a la "transpiración" de dicho símil estimada median
te la expresión:
TT =
VA
flujo
área foliar
45
Cuadro 6 .
M e d i c i o n e s h e c h a s a un símil d e p l a n t a d e m a í z d e p a p e l filtro.
Area F o l i a r :
1 6 6 9 cm2.
Temperatura
Entrada
Salida
("C)
("C)
Concentración de vapor de agua
Ehtrada
Salida
ACYA
(9i3)
(Sm-9
1
< t p i
(pg Qn-2S-l)
Flujo: 128.2 i/min
1
2
3
4
5
6
7
8
9
10
-3.7
-3.4
-3.8
-3.4
-3.6
-3.3
-3.2
-3.5
-3.3
-3.4
-1.6
-1.6
-1.6
-1.7
- 1 .5
-1.7
-1.9
-2.1
-2.0
-1.8
3.740
3.820
3.713
3.820
3.766
3.847
3.875
3.793
32 4 7
3.820
4.337
4.337
4.337
4.307
4.368
4.307
4.247
4.188
4.217
4.277
O . 597
0.517
O. 624
O. 487
0.602
0.460
0.372
O . 395
0.370
O .457
O. 764
O ,662
O. 799
O . 624
0.77i
O. 589
0.476
O . 506
0.474
O. 585
O. 690
O . 694
O. 631
O. 664
O . 546
0.631
O .499
O . 759
O .668
O . 550
0.470
O. 473
0.430
0.452
0.372
O. 430
O. 340
0.517
0.455
O. 375
O . 585
O. 582
o. 551
O. 605
O .609
0.530
O. 554
0.521
O . 554
O . 582
0.281
O. 280
0. 265
O . 291
O. 293
o. 255
O. 266
o. 251
O. 266
O. 280
Flujo: 68.2 Urnin
1
2
3
4
5
6
7
8
9
10
-4.4
-4.3
-4.4
-4.3
-4.3
-4.4
-4.0
-4.2
-4.2
-4.2
-1.9
-1.8
-2.1
-1.9
-2.3
-2.1
-2.2
-1.5
-1.8
-2.2
3.557
3.583
3.557
3.583
3.588
3.557
3.660
3.609
3.609
3.609
4.247
4.277
4.188
4.247
4.129
4.188
4.159
4.368
4.277
4.159
Flujo: 48.2 l h i n
1
2
3
4
5
6
7
8
-3.2
-3.3
-3.3
-3.5
-3.4
-3.0
-3.2
-3.3
-1.2
-1.3
-1.4
-1.4
-1.3
-1.2
-1.3
-1.5
10
-3.3
-1.3
9
-3.2
-1.3
3.875
3.847
3.847
3.793
3,820
3.930
3.875
3.847
3.875
3.847
4.460
4.429
4.398
4.398
4.429
4.460
4.429
4.368
4.429
4.429
46
uadro 7 .
M e a i c i o n e s h e c h a s a un s í m i l d e p l a n t a d e cártamo d e p a p e l
filtro.
Area F o l i a r :
1 6 2 5 cm2.
Temperatura
Entrada
Salida
("C)
Entrada
1
("C)
Concentración de vapor de agua
Salida
ACVA
In"
(9m-3>
('3 m m 3 )
(Jig Qn-'2s-')
Flujo: 128.2 Urnin
1
2
3
4
5
6
7
8
9
10
-3.5
-3.2
-3.3
-3.3
-3.3
-3.2
-3.1
-3.2
-3.1
-3.0
-2.1
-1.8
-1.9
-1.8
-1.8
-1.6
-1.6
-1.7
-1.4
-1.5
3.793
3.¿75
3.847
3.847
3.847
3.875
3.902
3.875
3.902
3.930
4.188
4.277
J . 247
4.277
4.277
4.337
4.337
4.307
4.398
4.368
O. 395
O. 402
O. 400
O. 430
0.430
O. 462
0.435
0.432
0.496
O. 438
0.519
O. 529
O. 526
O. 565
O. 565
O. GO7
0.572
O. 568
O. 652
O. 576
O. 609
o. 551
O. 609
O. 554
0.613
O. 609
O. 493
O. 609
O. 605
0.613
0.426
O. 385
0.426
0.387
O .429
G.426
0.345
0.426
0.423
0.429
O. 554
O. 624
O. 585
O. 624
O. 648
O. 624
O. 593
O. 561
O. 621
O. 624
O. 274
O. 308
O. 289
0.308
0.320
0.308
O. 253
a. 277
O. 307
O. 308
m
Flujo : 68.2 l/min
1
2
3
4
5
6
7
8
9
10
-3.4
-3.3
-3.4
-3.2
-3.3
-3.4
-3.2'
-3.4
-3.5
-3.3
-1.3
-1.4
-1.3
-1.3
-1.2
-1.3
-1.5
-1.3
-1.4
-1.2
3.820
3.847
3.820
3.¿375
3.847
3.820
3.875
3.820
3.793
3.847
4.429
4.398
4.429
4.429
4.460
4.429
4.368
4.429
4.398
4.460
0.586
Flujo: 48.2 l/min
1
2
3
4
5
6
7
8
9
10
-3.2
-3.O
-3.2
-3.0
-3.2
-3.0
-3.0
-3o.
-3.1
-3.0
-1.3
-0.9
-1.2
-0.9
-1.o
-0.9
-1.o
-1.1
-1.o
-0.9
3.875
3.930
3.875
3.930
3.875
3.930
3.930
3.930
3.902
3.930
4.429
4.554
4.460
4.554
4.523
4.554
4.523
4.491
4.523
4.554
m
47
donde e l á r e a f o l i a r s e r í a e n e s t e c a s o , l a s u p e r f i c i e e v a p o r a t i v a d e l papel f i l t r o .
L a t a s a de e v a p o r a c i ó n c a l c u l a d a a d i s t i n t o s f l u j o s de a i r e s e m u e s t r a n en los C u a d r o s 8 y 9 y s e i l u s t r a n en l a F i g . 9 .
Cuadro 8,
Tasa de e v a p o r a c i ó n (TE) a d i s t i n t o s f l u j o s de a i r e
a t r a v é s d e l a c á m a r a d e a s i m i l a c i ó n e n un s í m i l d e
p l a n t a h e c h o con p a p e l f i l t r o .
CVA ( e n t r a d a )
Flujo
(LPM)
TE
-2s-1)
(ilg cm
ígm-3)
48.2
3.9120.03
68.2
128.2
CARTAMO
Rango
O . 3020 . O 1
O . 29-0.31
3.8320.03
0.4120 . O 3
O. 39-0.44
3.7820.04
O . 5720.04
0.53-0.61
3.8620.03
0.2720.01
O . 26-0.28
68.2
3.5920 . O 3
0.4320.05
0.38-0.48
128.2
3.8050.05
O .6220.12
O . 50-0.74
MAIZ
L o s d a t o s a n o t a d o s e n e l C u a d r o 8 c o n f i r m a n que una sup e r f i c i e e v a p o r a n t e s i n e s t o m a s y b a j o un f l u j o d e a i r e con
c i e r t a c o n c e n t r a c i ó n d e v a p o r d e a g u a , aumenta s u t a s a d e e v z
p o r a c i ó n a l e l e v a r e l f l u j o de a i r e c i r c u l a n t e a t r a v é s de l a
cámara.
Dado que e s t a e v a p o r a c i ó n sólo e n c u e n t r a l a r a , e s
e v i d e n t e que l o s aumentos e n f l u j o d e b e n o c a s i o n a r una d i s m i nución en r
a
.
J
48
Cuadro 9.
Resistencia de la capa frontera (ra) a distintos
flujos a través de la cámara de asimilación en
un símil de planta'de maíz y cártamo hechos con
papel filtro.
Flujo (LPM)
Resistencia de la capa frontera (ra )
(s cm-1)
M a í z
C á r t a m o
48.2
2.10
2.02
68.2
1.47
1.43
0.79
0.76
128.2
Como se observa en el Cuadro .9, efectivamente la ra disminuyó conforme se incrementó el flujo de aire a través de la
cámara de asimilación conteniendo la muestra de papel filtro.
En cónsecuencia, el sistema diseñado es capaz de reproducir
diferentes condiciones ambientales en cuanto a velocidad del
viento y la correspondiente r
a
para cada especie.
Bell e t d. (1973) encontraron una r
de 0.14+0.02 s cm-l
a
en un sistema portátil que diseñaron para medir fotosíntesis
y rs de la hoja para hojas anfiestomáticas.
Otros autores (Parkinson e2 a e . , 1980) obtuvieron una ra
de 0.15 a 0.31 para otro sistema portátil, valores que consideraron aceptablemente pequeños, aunque reconocieron que variaban dentro de la cámara, dependiendo de la distancia entre
el ventilador y la muestra.
Estos autores tampoco controla-
49
Ccm
8-1)
ro
2 .o
I .o
Tasa de Evapomcidn
(TE)
-
50
ron la temperatura de la hoja, pues consideraron que el diseño y selección de los materiales a medir, permanecieran
muy cercanos al de aquellas hojas no encerradas en la cámara.
En el sistema aquí diseñado se hace la misma consideracibn, pues aunque no se controló la temperatura foliar, el
aire circulante a través de la muestra era previamente homogeneizado en un tanque de 200 1 y obtenido del ambiente externo a unos 5 m de altura.
CBilculo de la resistencia estomatal (ra)
Dado que el flujo transpiratorio en plantas pasa por dos
resistencias, la ra y la r s , con los datos anteriore.8
(Cuadro
-
9) surge la pregunta si el’ flujo circulante en-la cámara de . .
asimilación también ocasiona camb-ios en-r 8
.
Por lo anterior, una vez obtenida la resistencia de capa
frontera (ra),
se procedib a calcular r 8 , a partir de la ecua
ción para TT considerada como proceso difusivo:
TT =
-r
AVA
a
despejando rs:
rS =
+ r
AVA
TT
S
- ra
Los valores estimados de rs se anotan en el CuadroLO.
I
3
51
Cuadro 1 0 . Resistencia estomatal (rs).
Resistencia estomatal (rs)
(scm-l
Flujo (LPM)
Maíz
Cártamo
48.2
-o. 3 2 b
-0.698
68.2
-0.244
-0.498
0.013
128.2
-0.160
Bajo las condiciones experimentales del presente trabajo, se encontró que las r
S
de maíz y cártamo fueron muy peque
ñas e incluso la mayoría de ellas con valores negativos; magnitudes negativas para r
S
en este caso se interpretan como
cero,
ya que no s e consideran factibles las r S negativas.
-
Es
-
to implica que para este sistema de gases, el cambio de flujo
a través de la cámara, no produce modificaciones en la rs de
las plantas.
Beadle
d. ( 1 9 7 3 ) midieron intercambio de gases en hg
jas solas de maíz y de sorgo a diferentes intensidades lumino
sas y 2 8 ° C con una cámara de asimilación pequeña, encontrando
TT a
260
pEm-2s'1
de 0 . 0 2 1
mg rnm2s'l
y una r total de la hoja
+ rS ) de aproximadamente 6 5 cm-l en ambas especies, en dona'(
de r = 0.05 scm-l bajo el diseño de los autores. Nótese que
a
con este sistema, si bien la ra es miniiscula, la rS en cambio
aumenta considerablemente.
52
e n c o n t r ó T T d e 5 a 6 Vg cm-2s-1
Con g i r a s o l A s t o n ( 1 9 7 6 )
y una r t o t a l a l a d i f u s i ó n
(ra
+
r ) e s t i m a d a d e 2 a 4 scm-l
S
m e d i a n t e e l uso d e una c á m a r a d e a s i m i l a c i ó n c o n s t r u i d a e n
a c r l l i c o c o n 216 dm3 d e c a p a c i d a d y e m p l e a n d o un p s i c r ó m e t r o
d i f e r e n c i a l p a r a r e g i s t r a r l a humedad d e l a i r e a l a e n t r a d a
y a l a s a l i d a d e la c á m a r a ,
y una r
a
d e 4 . 3 a 5 scm-l.
Medición d e t a s a t r a n s p i r a t o r i a y o t r o s p a r á m e t r o s c o n b a s e e n
porometría
Con e l f i n d e c o m p a r a r l o s r e s u l t a d o s o b t e n i d o s c o n e l
s i s t e m a d i s e ñ a d o c o n t r a o t r o método c o n o c i d o y aceptado,
se
midió l a TT y algunos otros parámetros con base en porometría.
-
Este método c o n s i s t i ó en tomar l e c t u r a s d e h o j a s ubica-
d a s e n d i s t i n t o s n i v e l e s d e l a p l a n t a c o n un p o r ó m e t r o m a r c a
LI-COR,
INC.
Modelo LI-1600,
e l c u a l m i d e r s , humedad r e l a ti
v a (€IR), t e m p e r a t u r a d e a i r e ( T a i r e )
una p e q u e ñ a s u p e r f i c i e f o l i a r
e l envéz.
planta
y transpiración (TT)
( 2 cm2),
en
y a sea e n e l h a z o e n
Con t a l p o r ó m e t r o se t o m a r o n t r e s m u e s t r a s e n c a d a
(de maíz y d e cártamo):
una h o j a d e l e s t r a t o s u p e r i o r ,
o t r a d e l medio y o t r a d e l e s t r a t o i n f e r i o r ,
estimándose l o s
v a l o r e s para e l haz y e l envéz en cada e s p e c i e ,
en condicio-
nes de laboratorio.
L o s r e s u l t a d o s o b t e n i d o s s e a n o t a n e n e l C u a d r o 11.
53
9 c4
oou
4 4 N
m-40
m m m
m m m
m m m
...
9 0 0 0
...
. .o.
m m w
...
UN00
hlmm
(d
\rl
L.4
U
aJ
a
O
L.4
O
...
a
4-44
o
999
4-4l-l
9)
al
rn
(d
P
fi
O
O
u
c
rn
O
&
u
N
aJ
a
\(d
4
...
...
O 0 0
O 0 0
NNN
NUQ)
Ei
m u u
H
...
O 0 0
NNN
m h l h
&
PG
(d
a
rn
O
kl
4
c
u
U
O
h
E-c
m m \
E-c
0)
a
O
a
4
9-l
o
II
Q)
s
....
m
m
rn
u
a m m m
m m m m
m u m u
00
....
N m m m
00u4-c
cv
m o o d
4thQ)cv
O
900U9
0 0 9 9 -
h
rn
O 0 0 0
O 0 0 0
O
....
....
+
aJ
L.4
O
r
l
-4
9
(d
3
O
4
A
4
IX
O
a
(d
3
U
-
N
w
U
n
IX
W
4
b
O
s
...
O 0 0
u m m h
....
-4ou00
Nmmcv
m m u
1
54
C á l c u l o d e l a r e s i s t e n c i a e s t o m a t a l (r
S
) con b a s e en p o r o m e t r f a
P a r t i e n d o de l o s v a l o r e s d e r e s i s t e n c i a a l a d i f u s i ó n d e
v a p o r d e c a d a l a d o d e l a h o j a , e s t i m a d o s con e l p o r ó m e t r o ,
c a l c u l ó l a r e s i s t e n c i a estornatal
p a r a cada e s p e c i e ,
se
( r s ) d e l a h o j a (ambas c a r a s ) ,
a saber:
1
r
1
a
S
r
+
haz
1
r
envéz
Tomando l o s v a l o r e s m e d i o s s e o b t u v i e r o n l o s d a t o s anot a d o s en e l C u a d r o 12.
Cuadro 1 2 .
Resistencia estomatal
-
r
S
(haz)
( s cm-1)
(r ) con b a s e e n P o r o m e t r í a .
S
r
(envéz)
S
( s cm-1)
r
S
(hoja)
( s cm-1)
~~
~
a
í
z
3.92
5.28
2.45
3.18
1.75
N ó t e s e en e l C u a d r o 13 q u e e n g e n e r a l l a t a s a t r a n s p i r a t o r i a d e c á r t a m o e s mayor q u e l a d e m a í z ,
como t a m b i é n s e ha-
b r í a d e t e c t a d o con e l s i s t e m a a q u í d i s e ñ a d o ; s i n embargo,
las
magnitudes de d i c h a s t a s a s son c o n s i d e r a b l e m e n t e mayores con
il
55
el método porométrico; estas diferencias se atribuyen a varias razones:
En porometría se mide una superficie foliar de sólo
2 cm
y de un solo lado de la hoja con una r
a hoja de
0.2 s cm- ; mientras que en el sistema aquí diseñado
se mide la planta completa (ambas caras de l a hoja) que
representa una superficie foliar mucho mayor y con una
r
a
variable según el flujo del aire circulante.
A g í , con el método porométrico, si bien se pueden detec
-
tar diferencias transpiratorias entre diferentes hojas
y aún entre diferentes posiciones de la hoja, difícilme:
te se puede estimar la transpiración promedio d e l a p l a n -ta.
Por el contrario, con la cámara y sistema diseñados,
la transpiración promedio por unidad de área foliar resulta la Única medición directa, de la cual no se pueden
inferir las diferencias entre hojas y entre sitios.
Por otro lado, el porómetro empleado también da información sobre temperaturas de la hoja y del aire, así como
la humedad relativa y la densidad de fotones fotosintsticamente activa,
Estas también podrían ser obtenidas
con la cámara de flujo abierto mediante la implementación de l o s sensores respectivos.
Sobre la rs de la hoja, cabe mencionar que ésta siempre
es menor que la rs de cada una de sus superficies, por lo que
56
-
l a comparación d e l a p o r o m e t r í a con e l o t r o método debe h a c e r
se c o n l a r
Turner
dad,
S
de l a hoja.
(1969)
observó r
s
e n m a í z d e muy a m p l i a d i v e r s i -
dependiendo de l a p o s i c i ó n de l a h o j a en l a planta.
una h o j a s u p e r i o r u b i c a d a a 2 . 5 0 m d e a l t u r a ,
l a r
S
En
era casi
c e r o ; m i e n t r a s q u e e n l a b a s e d e l a p l a n t a a u n o s 3 0 cm d e
altura,
l a rs e r a mayor a 1 0 0
m e d i a n t e e l u s o d e un poróme-
tro.
IZTAPALAP-A
SERVICIOS DOCUMENTALQ,
IV.
De l o a n t e r i o r m e n t e ,
1.
CONCLUSIONES
podemos c o n c l u i r l o s i g u i e n t e :
Se c o n s i d e r a q u e e l m é t o d o d e s c r i t o e s d e a l t a p r e c i s i ó n ,
y a que los e r r o r e s e x p e r i m e n t a l e s que se o b t i e n e n s o n
p r á c t i c a m e n t e i r r e l e v a n t e s y p u e d e n ser d e b i d o s a l a s c a r a c t e r í s t i c a s d e d i s e ñ o y c o n s t r u c c i ó n d e l a cámara d e
a s i m i l a c i ó n usada.
2.
Es un m é t o d o c a p a z d e m e d i r t a s a s t r a n s p i r a t o r i a s muy r e ducidas,
p o r l o q u e p u e d e t r a b a j a r s e c o n p l a n t a s más p e -
queñas que l a s u t i l i z a d a s e n e s t e e x p e r i m e n t o .
3.
P o r l a s d i m e n s i o n e s d e l a cámara d e a s i m i l a c i ó n ,
e s po-
s i b l e t r a b a j a r con p l a n t a s d e maíz, cártamo y e s p e c i e s
si
m i l a r e s a é s t a s h a s t a d e 6 5 cm d e l o n g i t u d d e l t a l l o c o n
entrenudos con h o j a s a c t i v a s .
4.
E l m é t o d o p e r m i t e s i m u l a r una a m p l i a gama d e c o n d i c i o nes n a t u r a l e s en cuanto a v i e n t o e iluminación.
5.
E l m é t o d o además p r o p o r c i o n a m e d i c i o n e s d e l g a s t o t o t a l
d e agua d e l a p l a n t a o p o r unidad d e á r e a f o l i a r .
58
BIBL IOGRAF IA
ASTON, M.J. (1976). Variation of stomatal diffusive resistance
with ambient humidity in sunflower. Aust. J. Plant
Physiol. 3:489-501.
BEADLE, C.L., Stevenson, K.R., Newmann, H.H., Thurtell, G.W.
and King, K.M. (1973). Diffusive resistance, transpiration and photosynthesis in single leaves of corn and
sorghum in relation to leaf water potencial. Can J.
Plant Sci. 53:573-544.
BEADLE, C.L., Stevenson, K.R., Thurtell, G.W. and Dub6 P.A.
(1974). An open system for plant gas-exchange analysis.
Can J. Plant Sci. 54:161-165.
BELL, C.J. and Incoll, L.D. (1981). A handpiece for the
simultaneous measurement of photosynthetic rate and leaf
diffusive conductance. J. Exp. Bot. 32:1125-1134.
DEVUN, R.M.
(1970).
Fisiología Vegetal (0mega:Barcelona).
GONZALEZ, H.V. (1982). Sorghum responses to high temperature
and water stress imposed during panicle development.
Ph.D. Dissertation.
JANAC, J. (1971). Construction of infrared Cop analysers. En:
Plant phosotynthetic production. Manual of methods
(Eds. Z. Sestak, J. Catsky y P.G. Jarvis), pp. 118,119.
(Zuid-Nederlandsche Drukkerij N.V., s-Hertogenbosch).
LIVERA, M.M. (1985). Physiological responses of sorghum to
its environment. I. Long threm effects of suboptimal
temperatures on development. 11. Measuring conductance
and water vapor en Cop exchange canopies.
LONG, S.P. (1982) Measurement of photosynthetic gas exchange.
En: Techniques in bioproductivity and photosynthesis
(Eds. J. Coombs y D.O. Hall). pp. 25-34 (Pergamon Press:
Inglaterra).
LUDLOW, M.M. (1982). Measurement of solar radiation, temperature and humidity. En: Techniques in bioproductivity
and photosynthesis (Eds. J. Coombs y D.O. Hall), pp. 5-16.
(Pergamon Press: Inglaterra).
ORTIZ C.,J.,Mendoza O . , L. y Gonzáiez H., V. (1984).
tecnia en la formaci6n de arquetipos vegetales.
y Desarrollo 60:-15-124 (CONACYT).
La FisioCiencia
PARKINSON, K.J., Day, W. and Leach, J.E. (1980). A portable
system for measuring the photosynthesis and transpiration of graminaceous leaves. J. Exp. Botany. 31:1441-1453.
1
i
59
TURNER,
N.C. (1969). S t o m a t a l r e s i s t a n c e t o t r a n s p i r a t i o n in
t h r e e c o n t r a s t i n g canopies. C r o p Sci. 9: 303-307.
A N E X O S
ANEXO 1
__
._
-
- __
--
- .__
-
DENSITY OF PURE WATER VAPOR Ai' SATURATION OVER WATER
TUTI.
Perr.
ture
.#-
Ir.
10
.
g.ma
g.a.4
.4
.5
.6
6.rn.a
5.m.J
g.m.4
t~~.~gg.m-'
7J65 7212
7.649 7.699
8163 8216
8.7% 8362
9280 9.339
9.459 9.519
10.08 10.14
10.73 10.79
11.42 11.49
12.14 12.22
9.579
10.20
10.86
11.56
12.29
9.641
10.27
10.93
11.63
12.37
17
18
19
12.83
13.63
14.48
15.37
16.31
12.91
13.72
14.57
15.46
16.41
12.99
1380
14.65
15.55
16.50
13.07
13.88
14.74
15.65
16.60
13.14
13.97
i4.B
15.74
16.70
1323
14.05
14.92
15.83
16.80
13.31
14.14
15.01
15.93
16.90
13.39 13.47
1422 14.31
15.10 15.19
16.02 16.12
17.00 17.10
20
21
22
23
24
17.30
18.34
19.43
20.58
21.78
17.40
18.44
19.54
20.70
21.91
1750
18.55
19.65
20.81
17.60
18.66
19.77
20.93
22.16
17.71
18.77
19.88
21.05
2228
17.81
18.88
20.00
21.17
22.41
17.91
18.99
20.11
2129
18.02
19.10
20.23
21.42
18.12 1823
1921 19.32
20.34
20.46
25
26
27
28
29
23.05
24.38
25.78
2724
28.78
23.18
24.52
2592
27.39
28.93
2331
24.66
26.06
2754
23.44
24.79
26.21
27.69
29.25
23.58
24.93
2635
27.85
29.41
23.71
25.07
23.84
2521
2665
28.15
29.73
23.97
2535
26.79
28.31
24.11
25.49
26.94
29.89
28.46
30.05
24.24
25.63
27.09
2862
3022
30
31
32
30.55
32.24
34.01
3587
37.81
30.7l
32.41
34.19
38.01
31.05
32.76
34.38 34.56
3 6 ~3 6 . ~
3821 38.41
3122
32.94
34.74
36a
38.61
31.38
33
34
30.38
32.07
33.83
35.68
37.61
31.55
3329
35.11
37.02
39.01
31.72
33.47
3530
37.22
39.22
31.89
33.65
35.49
37.41
39.42
35
36
37
38
39
39.63
41.75
43.96
46.245
48.67
39.84
41.%
44.18
46.50
48.92
40.05
42.18
44.41
46.74
49.17
4026
42.40
44.64
46.97
49.42
40.47
42.62
44.87
4721
49.66
42.84
45.09
47.45
49.92
40.68
40.89
43.06
41.10
4338
45.56
47.94
50.42
41.31
43.50
45.79
48.18
50.67
41.53
43.73
46.02
48.42
50.93
40
41
42
43
51.45
51.70
54.36
57.12
60.00
51.96
54.63
57.40
52.49
55.17
57.97
60.88
63.92
52.75 53.01
55.44 -55.72
5825 58.54
61.18 61.48
64.23 64.55
53.54
63.M 63.31
5222
54.90
57.68
60.59
63.62
5328
56.00
58.83
44
51.19
53.82
56.56
59.41
62.39
45
46
47
48
49
65.50
68.73
72.10
75.61
79.26
66.13
6939
72.79
76.33
80.01
66.45
69.73
73.13
76.ó9
67.10
70.40
73.04
77.41
81.14
67.42
70.73
74.18
7737
81.52
68.07
71.41
74.89
7851
82.28
68.40
71.75
75.25
80.38
66.77
70.06
73.49
77.05
80.76
50
a.06 83.4s
ma
84.62
85.41 85.81 8620 w.60
89-45 89.86 9om 90.69
9323 93.66 94.09 94.52 94.95
97.59 98.03 98.47 98.92 9937
102.1 102.6 103.0 103.5 104.0
1OS.9
106.3
1112
116.2
1215
126.9
106.8
111.7
116.8
122.0
si
52
53
54
55
56
54.09
56.84
59.70
62.70
65.81
69.06
72.45
75.96
79.63
22.03
29.09
3606
a.w
87a2
30.88
32.59
60.29
87.01 87.41
8822 88.63
91.12 91.54 91.96 92.38 92.80
9539 95.83 96.27 96.71 97.14
99.83 100.3 100.7 1012 101.7
104.4
1092
57
58
59
114.2
119.4
124.7
60
130.3
104.9
109.7
114.7
119.9
1253
105.4
110.2
115.2
120.4
125.8
110.7
115.7
121.0
126.4
SYITHSONIAR YmOROLOGICAL TABLES
26.50
28.m
29.57
8.058
22.54
33.11
34.93
s.83
38.81
45.33
47.69
50.17
7.118
7.0
8.110
8.W
9.221
9.825
9
9.399
10.01
10.66
11.35
12.07
9.016
7.071
7.550
s
8.595
9,163
9.702 9.763
10.33 10.40
11.00 11.07
11.70. 11.77
12.44 12.52
8.485
7.025
7.501
8.006
8.540
9.104
3
6.979
7.452
7.954
.
6.832
7.307
7.801
8.321
8.875
.3
6.933
7.404
7.902
8.431
8.989
15
.
.
g.m.4
2
6.887
7.355
7.851
8.377
8.932
15
.
g.m.2
6.797
7.260
7.750
8.270
8.819
13
14
-
.1
5
6
7
8
9
11
12
..
.O
10.46
11.14
11s
12.60
22.66
67.74
71.07
74.53
78.14
81.90
9.887 9949
1053 fOS9
1121 1127
11.92 11.99
12.67 E 7 5
21.54
w 9
61.78
64.86
1355
14-39
15.28
1621
17.20
21.66
22.92
5627
59.12
62.08
65.17
78.88
82.67
85.01
69.04
127.5
107.3
1122
117.3
1226
128.0
107.8
112.7
117.8
123.1
U8.6
I
1082
1132
118.3
123.6
129.1
108.7
113.7
118.8
124.2
129.7
I
i
.'
,
.
.
-
DENSITY O F P U R E WATER V A P O R A T S A T U R A T I O N O V E R WATER
Tem-
Pen-
ture
'C.
-50
-49
-18
-47
-46
-45
-44
.l
2
g.m.4
g.m.a
g.m.4
0.06171
.3
g.m.-'
.4
.5
.G
.7
.8
g.m.2
g.m.4
g.m.-'
g.m.4
9.m."
0.06886 0.06812 0.06738 0.06664 0.06592
-43
-42
-41
-40
-39
-38
-37
-36
-35
-34
-33
-32
-31
-30
-29
-28
-27
-26
-25
-24
-23
-22
-21
-20
-19
-18
-1 7
-16
-15
-14
-13
-12
-11
-10
-- 98
--
.O
7
6
5
4
- 23
-1
- OO
1
2
3
4
0.07675 "0.07592
0.08544 0.08453
0.09501 0.09402
0.1055 0.1044
0.1172 0.1160
0.1298 0.1285
0.1438 0.1424
0.1590 0.1574
0.1757 0.1740
0.1940 0.1922
0.2141 02119
0.2359 0.2336
0.2597 022372
0.2856 02829
0.3138 o3108
0.3445 0.3413
0.3779 0.3744
0.4141 0.4104
0.4534 0,4493
0.4960 0.4916
0.5422 0.5374
05922 05871
0.6463 0.6407
0.7047 0.6986
0.7678 0.7612
0.8359 0.5289
0.9093 0.9017
0.9884 0.9802
1.O74 1.065
1.165 1.156
1.264 1.253
1.369 1.359
1.483 1.471
1.605 1.592
1.736 1.722
1.876 1.861
2.026 2.010
2.186 2.170
2358 2.340
2.541 2.522
2.737 2.717
2.946 2.925
3.169 3.146
3.407 3.383
3.660 3.634
3.930 3.902
4217 4.188
4.523 4.491
4.847 4.814
4.847 4.881
5.192 5.228
5.559 5.597
-5.947 5.987
6.250 6.402
0.07510
0.08364
0.09303
0.1033
0.1148
0.1272
0.1409
0.1559
0.1723
0.1902
02099
0.2314
0.2548
02802
0.3080
0.3382
0.3710
0.4067
0.4453
0.4872
0.5327
0.5820
0.6351
0.6927
0.7548
0.8218
0.8941
0.9720
1.056
1.146 .
1243
1.348
1.460
1.580
1.709
1.847
1.995
2.153
0.07430
0.08274
0.09205
0.1022
0.1136
0.1258
0.1395
0.1543
0.1706
0.1884
02079
O2291
0.2523
02776
0.3050
0.3350
0.3675
0.4029
0.4413
0.4829
0.5280
0.5768
0.62%
0.6867
0.7483
0.07350
0.08187
0.09107
0.1011
0.1124
4.1246
0.1380
0.1528
0.1640
0.1866
02058
02269
02499
02750
03022
0.3320
0.3642
0.3992
0.4373
0.4785
0.5234
0.5718
0.6242
0.6808
0.7420
0.8081
0.8792
0.9560
1.O39
1.128
1.223
1.326
1.437
1555
1.682
1.819
1.965
2.121
2288
2.466
2.657
2.8ól
3.078
3310
3.557
0.8150
0.8867
0.9640
1.O47
1.137
1233
1.337
1.448
1568
1.696
1.833
1.980
2.137
2.323 2.305
2.504 2.485
2.697 2.677
2.903 2.882
3.123 3.101
3.358 3.334
3.609 3.583
3.875 3.847 3.820
4.159 4.129 4.100
4.460 4.429 4.398
4.781 4.748 4.715
4.915 4.948 4.983
5264 5.300 5.336
5.635 5.673 5.711
6.028 6.068 6.109
6.445 6.488 6.531
0.06520
0.07270
0.08099
0.09011
0.1001
0.1112
0.1233
0.1367
0.1512
3.1673
0.1847
0.2038
02247
02475
02723
OB3
0.3289
03608
039%
0.4334
0.4743
0.5187
0.5668
0.6187
0.6749
0.7357
0.8012
0.8719
0.9481
1.030
1.119
1214
1.316
1.425
1.543
1.669
1ms
1.949
2.105
2271
2.448
2.638
2.840
3.056
3286
3.532
3.793
4.072
4.368
4.683
5.017
5.373
5.750
6.150
6.575
[Contmcrd)
SYITHSORIAH METEOROLOGICAL TABLES
.9
g.m.4
0.06449 0.06378 0.06309 O.Oú240
0.07191 0.071 15 0.07035 0.06961
0.08013 0.07927 0.07842 0.07758
0.08915 0.08822 0.08728 0.08635
0.09912
0.1101
0.1220
0.1353
0.1497
0.1656
0.1829
02019
0.2225
02451
02697
029ó6
0.3258
03574
0.3920
0.4295
0.4700
0.5141
0.5618
0.6133
0.6691
0.7294
0.7944
0.8645
09402
0.03812
0.1090
0.1208
0.1339
0.1482
0.1640
0.1811
0.1998
0.09702
0.1078
0.1196
0.1325
0.1468
0.1623
0.1793
0.1979
0.2204 0.2183
0.2428 02405
02672 0.2647
0.2938 02910
O3228 0.3198
03542 0.3510
0.3884
0.4256
0.4659
0.5096
0.5568
0.6079
0.6633
0.7232
0.7877
0.8573
09323
1.022 1.013
1.109 1.100
1204 1.194
1.305 1.295
1.414 1.403
1.531 1.519
1.656 1A43
1.791 1.777
1.93 1.920
2.089 2.073
2254 2.237
2.430 2.412
2.618 2.599
2.819 2.798
3.034 3.012
3263 3.239
3.507 3.481
3.766 3.740
4.043 4.015
4.337 4.307
4.650 4.618
5.052 5m7
5.409 5.446
5.789 5.828
6.192 6233
6.619 6.663
02883
0.6576
0.7170
0.7810
0.85C1
0.9246
1.005
1.091
1.184
1284
1.392
0.6519
0.7108
0.7743
0.8429
0.9170
1.507
1.630
1.7ó3
1.905
2.057
2220
2.394
2.579
2.778
2.990
3.216
1.495
1618
1.749
1.890
2.041
2203
2376
2.560
2.758
2.968
3.193
3.713
3.986
4 q
4.586
5.122
5.483
5.868
6275
6.707
.
OW
. GO1
0.1066
0.1183
0.1312
0.1452
0.16%
0.1775
0.1960
02162
02382
0.2621
03167
0.3477
0.3849 0.3814
0.4218 0.4179
0.4617 0.4575
0.5050 0.5006
0.5519 0.5470
0.6026 0.5974
3.456
.
!
..
.7
z
0.9966
1.082
1.175
1274
1.381
3.432
3.687
3358
4247
4.554
5.157
5521
5.901
6.317
6.752
F;
<
T
1
I ,
,. .'
J
INSTRUCTIONS O15-556872-A
J
MODELS 864 AND 865 NON-DISPERSIVE
INFRARED ANALYZERS
THIS INSTRUCTION MANUAL IS APPLICABLE TO THE FOLLOWING INSTRUMENTS:
MODEL 864 INFRARED ANALYZERS
1. Instruments with serial numbers of 194500-0101167 and above.
2. Lower-numbered instruments which have been updated through installation of the
637134 Gain-ZeroKit.
This kit, installed by a Beckman Industrial Corporation Service Representative,
includes: 638490 D.C. Amplifier Board, replacing original 633030 Amplifier Board;
633290A Filter/RectifierBoard, replacing original 633290 Filter/Rectifier Board; and,
GAIN Dual Potentiometer R4A-R4B,replacing original GAIN Single Potentiometer R4.
MODEL 865 INFRARED ANALYZERS
1.General-Purpose Analyzers
194501 Analyzers with serial numbers of 194501-011503 and above. 194503
Analyzers with serial numbers of 194503-1 O00144 and above. Also, lower-numbered
instrumentswhich have been updatedthrough installationof the 637134 Gain-ZeroKit.
This kit, installed by a Beckman Industrial Corporation Service Representative,
includes: 638490 D.C. Amplifier Board, replacing original 633030 Amplifier Board;
new-type633290 Filter/RectifierBoard, replacingoriginal 633290 FilteríRectifier Board;
and, GAIN Dual Potentiometer R4A-R4B,replacing original GAIN Single Potentiometer
R4.
2. Explosion-Proof Analyzers
194502 Analyzers with serial numbers of 194502-0100080 and above. Also,
lower-numbered instruments which have been updated through installation of the
following components: 638490 D.C. Amplifier Board, replacing original 633030
Amplifier Board; 635785 FilterlRectifier Board, repiacingoriginal 633290 Filter/Rectifier
Board; and, GAIN Dual Potentiometer R4A-R4B, replacing original GAIN Single
Potentiometer R4.
01985 Beckman Industrial Corporation
A Subsidiary of Emerson Electric Co.
. .
I -
PROCESS INSTRUMENTS DIVISION 0 BECKMAN INDUSTRIAL CORPORATION
FULLERTON, CALIFORNIA 92634
March 1985
840206
015556872
Printed in U.S.A.
t -:
. .
DANGER
POSSIBLE EXPLOSION HAZARD
This analyzer is of the type frequently utilized for the analysis of explosive gases. If
used for such gases, Beckman Industrial Corporation recommends that it be contained
in an explosion-proof housing. NFPA 496, ISA S12-4 and other similar United States
and international standards relating to purging are directed only to the invasion of
explosive gases into the analyzer housing from the outside atmosphere. These
standards do not address the abnormal release of explosive gases intentionally
introduced into the analyzer housing. There are no recognized standards addressing
such potential hazard.
If explosive gases are introduced into this analyzer, whether or not it is contained
within the explosion-proof housing, Beckman Industrial Corporation recommends that
the sample containment system be carefully leak-checked upon installation and before
initial startup, during routine maintenance and any time the integrity of the sample
containment system is broken to ensure the system is in leak-proof condition.
Leak-check instructions are provided in Paragraph 2.4.1.
DANGER
ELECTRICAL SHOCK HAZARD
Disconnect power before servicing.
WARNING
Tampering or unauthorized substitution of components may adversely affect electrical
safety of this product. Use only factory-documented components for repair.
FORWARD
By purchasing from Beckman Industrial Corporation, you have procured one of the finest
instruments available for your particular application. Experience indicates that its performance is directly related to the quality of installationand the knowledge of the user in operating
and maintaining the instrument. Therefore, we suggest that this manual be read thoroughly
before proceeding with installation and commissioning. If this is the first instrument of this
model or application in your facility, we also suggest that you purchase training and fieM
technical support from Beckman Industrial Corporation. This will ensure that your instrument
is installed and commissioned correctly and that your personnel are properly trained to
operate and maintain it at top performance.
The trouble/diagnosis section in this manual is designed to aid in isolation of an operating
problem to a specific area-sample conditioning, readout device, or analyzer. To aid in
isolating malfunctions and in minimizing down time, it is recommended that the spare parts
listed in this manual be maintained in your stock.
This product is covered by the factory warranty found on the inside back cover of this
instruction manual. Defective items that fail within the warranty period may be returned by
requesting a Return Goods Authorization (RGA)from a Beckman Industrial Corporation field
or factory service center.
E-
~ Z T A P A L A P - ~
SERYLCIOS DOCUMENTALES
:ONTEhTS
ECTlON
d
TITLE
PAGE
10DEL 864/865 ORDERlNG CODE
. . . . . .. . . ...
,i
,PECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . .
ii
'ONDENSED STARTUP AND
;TANDARDlZATlON PROCEDURE
)NE
. . . . .. . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . . . .
rwo
.
INSTALLATION . . . . . . . . . . . . . . . . . . .
Facility Preparation . . . . . . . . . . . . . . . . . . .
Outline and Mounting Dimensions . . . . . . .
Electrical Input/Output Connections . . . ..
Location . . . . . . . . . . . . . . . . . . . . . . . . . ..
Utility Specifications . . . . . . . . . . . . . . . .
Sample Inlet and Outlet Connections . . . . .
Calibration Gas Requirements . . . . . . . . .
Sample Handling . . . . . . . . . . . . . . . . . . . . .
Leak Test for Applications Involving
Explosive Gas Samples . . . . . . . . . . . . .
Sample Flow Rate . . . . . . . . . . . .. . . . . .
2.4.2
Stacked Sample Cells . . . . . . . . . . . .. . . . .
2.5
Differential Analysis with Flow-Through
2.6
Reference Cell . . . . . . . . . . . . . . .. .. . ..
Liquid Sample Cells... .. .. . .. . . . . . . ..
2.7
Electronic Response Time Selection . . .. . .
2.8
Recorder Cable Connections . . .. . .
.
2.9
646093 Range I.D. Cable Assembly
2.10
(Optional) ..........................
646095 Remote Range Kit (Optional) . . . .
2.11
Purge Connections and Requirements for
2.12
General-Pürpose Model 864/865 . . .. .
Optional Purge Kit for
2.13
Explosion-Proof Model 865 . . . . . . . . .
Electrical Power Connection .. . . . . . ..
2.14
2.14.1 Model 864 and General-Purpose Model 865
2.14.2 Explosion-Proof Model 865 . . . . . . . . . . . .
1.1
2.1.1
2.1.2
2.1.3
2.1.4
2.2
2.3
2.4
2.4.1
.
.
.
.
.
3.1
3.2
1
2
2
2
2
2
5
5
5
6
. .
.
6
7
7
.
. . .. .
8
8
9
9
..
THREE
iü
. .
.
..
.
STARTUP . . . . . . . . . . .. .. . . . . . . . . .. . .
Detailed Startup and Calibration
Procedure .. . . . .. . . . .. . . . .. .. . . . ..
Checking interfering Components of the
Sample Stream .. . . . .. .. . . ... .. .. . ..
9
9
9
10
10
10
10
11
11
16
FOUR
17
OPERATION .......................
Routine Operation . . . . . .. .. . .. . . .
17
Recommended Calibration Frequency . . .. 17
Shutdown . . . . . . . . . . .. . . . . . . . . . .
17
FIVE
5.1
5.2
5.2.1
INSTRUMENT THEORY
Detection System . . . . .. .. .. . .. .. ... ..
Electronic Circuitry . .. .. . . . .. . . .. ... ..
633296 Oscillator Circuit Board and
Associated Elements of AmplitudeModulation Circuit .. . . ... . ... . ... ..
633290 or 635785 FilterIRectifier Board
and Associated Elements . . . .. . . .. . .
638490 D.C. Amplifier Board and
Associated Circuitry . . . . .
. .. ...
630153 Current Output Board (Optional)
633756 Voltage iinearizer Board (Optional
616443 Voltage Linearizer Kit) . . . . ... .
4.1
4.2
4.3
5.2.2
. 5.2.3
5.2.4
5.2.5
.. . .
. ..
. . . .. . ..... .. .
.
. .
. . ..
..
..
18
18
18
18
19
22
23
23
SECTION
5.2.6
TITLE
PAGE
638436 mA Linearizer Board (Optional
.
616442 mA Linearizer Kit) . . . . . . . . . .
5.2.7
633842 t15.5 Volt/-15 Volt
Power Supply ......................
637861 or 637862 Regulated A.C. Source
5.2.8
Power Supply, Front-Panel SOURCE
BALANCE Adjustment, Outsf-Phase
Adjustment, and Optical Shutters . . . . . .
631688 Detector Temperature Control
5.2.9
Board and Associated Elements
. ..
5.2.10 635883 Case Temperature Control Board
and Associated Elements
(Model 865 Only) . . . . . . . . . . . . . . . . . ,
5.2.11 633920 Calibration Power Supply and
Associated Elements of Optional Gasiess
Calibration Accessory . .. . . . .. .. .
5.2.12 646093 Range I.D. Cable Assembly
(Optional) ........................
5.2.13 646095 Remote Range Kit (Optional) . . .
. .. . .
.
.
..
..
.
23
23
23
25
25
25
25
25
*
M O D E L 864/865 ORDERING CODE
The Model 864/865 is ordered by a code number consisting
of the model number, the appropriate application number,
and the option number(s),as shown below.
Applications utilizing cells with length of five inches
( 1 28 mm) or less are available in both Models 864 and 865.
Applications utilizing cells with length of greater than five
inches (128 mm) are available only in the Model 865, as
indicated by an asterisk (*I following the application
number.
~
864
OR
865
MODEL 8641865 ANALYZER
RANGE CONFIGURATIONS (SELECT ONE ONLY)
iPTION
UMBER
~~
DESCRIPTION
~
'PLICATION
NUMBER
10
11
12
13
14'
15*
16*
18
19'
21
22
23
24.
25*
26
27*
31
32
33
34
35
36
38
39
PARAMETER
RANGE
O t o 1%
and O t o 5%
0 to 1000p1106and 0 t o 5000 pi106
and O t o 5%
Oto 1 %
O to 10%
and O t o 100%
O to 100 pi106 and O t o 1000 pi106
O to 50 PI106
O to 2OOp1106 and 0 t o lOOOpl106
O to 2%
and O t o 10%
O to 50 ~1106
O to 500 ~ 1 1 0 6and 0 t o 2500 pIlO6
O to 0.5%
and 0 t o 2.5%
O to 5%
and O t o 20%
0 to 100 PI106 and O t o 500 pi106
250 to 350 PI106 and O t o 600 ~ 1 1 0 6
0 to 20%
and O t o 100%
O t o 10 PI106 and 0 t o 100 PI106
O t o 2000 ~ 1 1 0 and
6 0 t o 10 000 pi106
0 t o 2%
and 0 t o 10%
O t o 10%
and O t o 50%
0 to 20%
and 0 t o 100%
0 t o l%,Oto 5% and 0 t o 15%. 0 to 20%
0 t o 5000 pi1Q6and 0 t o 5000 pi1@
0 t o 2%
and 0 t o 6%
0 t o 5%
and 0 t o 20%
-
41
42
43
44*
O t o 1000 PI106 and 0 t o 5000 p l l @
O to 1%
and 0 t o 5%
54*
55*
0 t o 2000 PI106 and 0 to 1 O 000 p/106
0 to 2%
and 0 to 10%
O to 500 ~ 1 1 0 6and 0 to1 2000 p1106
0 to 10%
and 0 t o 30%
Oto2000pi106andO t o 10000p/lOf
0 to 1%
and 0 t o 5%
0 to 500 pi106 and 0 t o 2000 p l l @
O to 0.5%
and 0 t o 2%
0 to 200 pi106 and 0 to lo00 ~ 1 1 0 ~
56*
63
64*
65*
66*
71
72*
81
82
83*
84*
85*
91*
92*
95*
SPECIAL
20
0 t o 2%
and 0 t o 10%
0 t o 2%
and 0 t o 10%
0 t o 2000 pIl06 and 0 t o 10 000 p/10(
0 t o 2%
and 0 t o 10%
(SELECT FROM € l i H € R A CURRENT
OR VOLTAGE OUTPUT OPTION,
PLUS ANY REMAINING OPTIONS.)
1
Linearirer Circuit (Voltage Output Uncalibrated): Provides linear output for
one range. Meter is also linear with concentration when this accessory i s used.
2
Linearizr Circuit ( V o l ~ Output,
p
Calibrated): Same as Option 1 except board
i s adjusted t o instrument output fineludes calibration curve).
3
Internal Span Calibrator: Permits spanning of analyzers without use of calibration gas.
4
Calibration Curve: One per range, if
other than standard ranges.
5
Current Output Borrd: Supplies 4 t o 20
mA and 10 t o 50 mA D.C. signal for
current-type recorders.
6
Bench Mounting Kit: Includes four
enclosure feet isupplied loose).
8
Type 2 Air Purge Kit:** For generalpurpose case. Complies with NFPA
AUTOMOTIVEAPPLICATIONS
a 2
0 t o 5%
and O t o 20%
j
496-1974.
9
1
11
Voltage Output Board O t o 1 VDC.
j
12
Linurirer Circuit (Current Output,
Unulibmted): Provilinearized 4 t o
20 m A or 10 t o 50 mA D.C. output for
one range. Meter is also linear with concentratim.
!
13
0to2000p/1@and0to10000p/10'
0 t o 2%
and 0 t o 10%
0 to 300 pi106 and 0 t o 1500 PI106
0 to 3000 p I 1 O 6 a n d 0 t o 1.5%
0 t o 5%
0 to 0.2%
and 0 t o 0.5%
I
Explosion-Proof Cur: FM-approved for
Class I, Groups B, C, and D, Division 1 ,
hazardous locations (Model 865 only).
I
i
Linwiru Circuit (Current Output, Calibmtod): Same as Option 12 except
board is adjusted t o instrument output
!
fincludes tmlibntion curte).
1s
16
17
Rang. Id.ntifiation: Identifies rang. t o
a remote data acquisition device.
Remote Range 'Switching:
ranges.
For three
I
I!
Single Range Switch
I
I
*Configuration available only in Model 865.
**Type X Purge Kit also available for general purposecese. Complies with
NFPA 496-1974 and CENELEC Standard EN 50 016 (1977).- Order
separately by the appropriate part number: 115 Volt PIN 645434
220 Volt PIN 646655
!
*
i
I
I
I
i
S PECIF ICATI O N S
MODEL 864
MODEL 865
Precision
1% of fullscale
Noise
Zero Drift **
Span Drift **
Response Time (Electronic)
1% of fullscale
1% of fullscale
+1%of fiillscale per 24 hours
+1%of fullscale per 24 hours
Variable, 90% in 0.5-second to 26 seconds, field-selectable
I 1 % of fullscale per 24 hours
21% of fullscale per 24 hours
Variable, 90% in 0.5-second to 26 seconds, field-selectable
Maximum Sensitivity
500 p/106 fullscale carbon monoxide
50 p/106 fullscale carbon monoxide
1% of fullscale
(pressurizedcell)
350 p/106 fullscale carbon dioxide
10 p/106 fullscale carbon dioxide
(pressurizedcell)
Materials in Contact with Sample:
windom
cells
Tubing
Sapphire, quartz, irtran
'
Stainless steel, gold-plated stainless steel
FEP Teflon.
I
Fittings
O-Ring>
316 Stainless steel
Viton-A*
Sample Flow Rate
Sample Pressure
Nominal 500 to lo00 cc/min
Maximum 15 psig (103 kPa)
Ambient Temperature Range**
30°F to 120OF (-1OC t o +49OC)
Analoa Output:
StarKlard ipotentiomatric)
~~
Optional (Current)
Optional (Linear Potentiometric)
O p t i o ~(Linen
i
Current)
Power Reauirements
Enclosure
-
Overall Dimensions
(Higherpressures used in pressurized
cell aDDlicationsl
..
Sapphire, quartz, irtran
Stainless steel,gold-plated stainless steel
F EP Teflon* (generalpurpose)
316 Stainless steel (explosionproof)
316 Stainless steel
Viton?A*
Nominal 500 to 1000 cclmin
Maximum 15 psig (103 kPa)
(Higher pressures used in pressurized
I
cell aodications
..
30°F to 12OoF (-1OC to +49OC)
O to 10 mV, O to 100 mV, O to 1 V, O t o 5 VDC (field sel6ctable)
4 to 20 mA, 10 to 50 mADC (fieldselectable)
O to 10 mV, O to 100 mV, O to 1 V, O to 5 VDC (fieldselucmble)
4 to 20 mA, 10 to 50 mADC (fieldselectable)
115 215V rms 50/60 20.5 Hz
115 k15V rms, 50/60 tO.5 Hz.
230 watts
200 watts average, 500 watts maximum
General purpose for installation in
194501 General purpose for installaweather-protected area
tion in weather-protected area.
194502 Explosion-proof, Class I,
Groups B. C. and D, Division 1.
8-11/16 inches (220 mm) H
134501 8-11/16 inches (220 mm) H
13-1/8 inches (333 mm) W
13-1/8 inches (333 mm) W
22-3/8 inches (569 mm) D
27-3/8 inches (696 mm) D
194502 See Figure 2 3
50 pounds (23 kg)
194501 61 pounds (28 kg)
-
-
-
instrument Weight
Shipping Weight
-
65 pounds (29 kg)
194502
194501
194502
*Tiadamarkof E. I. du Pont d. Namoun & Co.
**Prformanasp.sifiutiona b m d on ambient tamwritura a h i h of lesa than 2OoF I1l°C)
n d to r.ca1ibr.t..
- 155 Pounds (70 kg)
- 81 pounds (37 kg)
- 185 prnindr (83kg)
at a maximum rata of ZO°F I11 OC) par hours. without
COMPLIANCES: The general purpose Models 864 and 865 are constructed to meet the applicable requirements of the Ocarpat i m a l Safety and Health Act of 1970 if installed in accordance with t h e requirements of the National Electrical Code (NEC) in
non-hazardousareas and operated and maintained in the recommended manner.
T k Model 864 i s certified by Canadian Standards Association (CSA) as complying with the applicable standards for
protection against electrical shock and fire hazards in non-hazardous (ordinary) locations.
The air purge accessory for the Models 864 and 865 is designed for application with user-suppliedcomponents to comply wiU~
National Fire Protection Association (NFPA) 496-1974? to reduce the classification within an enclosure from Division 2,
normally non-hazardous, to non-hazardous. This principle i s recognized in the National Electrical Code (NEC)-1981in articles
500-1 and 501-3 (a).
The explosion-proof Model 865 is approved by Factory Mutual Research (FM) for use in Class I Groups B, C, and D,
Division 1 hazardous locations and will be deemed "approved" within the meaning of the U.S. Occupational Safety and Health
of 1970, if installed in accordance with the requirements of the National Electrical Code (NEC) for such locations and
operated and maintained in t h e recommended manner.
*The standard la not applicabla to applications involving tha introductionof flamrnabla umpln into tha ancloaura. S a DANGER noticm on irnida
front covar.
ODELS 8634 AND 865 NON-DISPERSIVE INFRARED ANALYZERS
Condensed Startup and Standardization Procedure
CA U T I 0N
DO NOT OPERATE MODEL 865 EXPLOSION-PROOF ANALYZER
WITHOUT LENS COVER AND DOOR I N PLACE WITH ALL BOLTS
SECURED, UNLESS LOCATION HAS BEEN DETERMINED TO BE
/\ION-HAZARDOUS
4
.-'
Prior to shipment, this instrument was subjected to extensive factory performance testing, du
necessary optical and electrical adjustments were made.
The following instructions are recommended for initial startup and subsequent standardizati
Model 864/865. In most cases, these simple instructions are sufficient for operation of the an
detailed instructions giyen in Section Three are n ed only if the optical bench alignme
disturbed, as could possibly occur during shipment.
NO TE
The following instructions contain several refe
This range is calibrated in most of the instruments shipped. in a few instruments, however, Range 1 is poJ calibrated. With an instrument of this type,
d
SECTION ONE
INTRODUCTION
A Model 864 or Model 865 Non-Dispersive infrared
Analyzer continuously determines the concentration of a
particular component o f interest in a flowing mixture. The
analysis is based on a differential measurement of the
absorption o f infrared energy. The instrument has a wide
range of applications, subject only to the limitation that the
analysis involve the determination o f a single component,
which must absorb infrared energy.
The Model 864, Figure 1-1,is provided in a generalpurpose enclosure. The Model 865 is available in either of
two enclosures: general-purpose, Figure 1-2;or explosionproof, Figure 1-3. All three versions are functionally
identical.
Within the analyzer, two equalenergy infrared beams are
directed through two optical cells; a flowthrough sample
cell; and, a sealed reference cell. Solid-state electronic
circuitry continuously measures the difference between the
amounts of infrared energy absorbed in the two cells. This
difference is a measure o f the concentration of the component o f interest in the sample. Readout is on a frontpanel meter with O-to-100 scale. In addition, a fieldselectable output for a potentiometric (voltage) recorder is
provided as standard. A field-selectable output for a
current-type recorder or controller is obtainable through
use of an optical plug-in circuit board.
A calibration curve can be used to convert meter or
recorder readings into concentration values. Alternatively,
the analyzer may utilize an optional plug-in linearizer
circuit board to equip a given operating range for linear
readout of concentration values on the meter and on a
recorder. The linearizer board is available in both voltage
output and current output versions.
For convenient routine upscale calibration, the analyzer
may incorporate an optional gasless calibration accessory.
Depression o f a pushbutton inserts a neutral density fiter
into the sample beam. The filter absorbs a fured amount of
infrared energy out of the beam, to simulate a specific
concentration of the measured component.
Figure 1-1. Model 864 Non-Dispersive Infrared Analyzer
As an option, the analyzer may be equipped for remote
selection of ranges.
The electronic circuitry utiüzes plug-in printed circuit
boards with solid-state components. This feature provides
the ultimate in reliability, facilitates servicing, and permits
the inclusion o f various options, such as current output, by
addition of the appropriate boards.
e C ..)
I.
Figure 1-2. General-Purpose Model 865 Non-Dispersive Infrared
A naly zer
3gure 13. ExplosionProof Model 8 6 5 Non-Dispersive Infrared
Analyzer
1
+f
SECTION TVVO
INSTALLATION
2.1.3
2.1 FAClLlTY PREPARATION
2.1.I OUTLINE AND MOUNTING DIMENSIONS
For mounting dimensions, refer t o Figure 2-1,Model 864;
Figure 2-2, General-Purpose Model 865; or Figure 2-3,
Explosion-Proof Model 865.
2.1.2 ELECTRICAL INPUT/OUTPUT CONNECTlONS
For electrical inputloutput connections, refer to Figure 24,
Model 864 and General-Purpose Model 865; or, Figure 2-5,
Explosion-Proof Model 865.
LOCATION
Analyzer
Preferably, the analyzer should be mounted near the sample
stream, to minimize sample-transport time. Of two or more
alternative installation sites, select the one least subject to
vibration.
A thermistorcontrolled heating circuit holds internal
temperature o f the analyzer t o the correct operating level
for ambient temperatures in the range of +30°F to +1 20°F
(OOC to 49OC). Temperatures outside these limits necessitate use of customer-supplied temperaturetontrolling
equipment or environmental protection.
DWG 630838
A.
B.
C.
D.
E.
F.
G.
Bracket L hardware f o r panel
mounting supplied by Beckman.
Recorder cable, 10 f t . long supplied
by BECICMAN I N D W f A L Coup.
Sample i n l e t
(Bulkhead f i t t l n g
f o r 1/4 (6 mn) O.U. TUbing.1
120 VAC input (supplied by
W K M A N IN DLJSWIALCORP,),
Sample o u t l e t
(Bulkhead f i t t i n g
f o r 1/4 (6 mn) 0.0. Tubing.)
Source voltage adjustment.
Bumpers supplied f o r bench mount appltcation.
Optional purge k l t (1/4-18 FPT).
ti
L.
M.
1.
2.
3.
4.
5.
6.
'
I
A l l dimensions i n inches W 1 6 , millimeters 11.5 mn.
Recomnended panel cutcut 12 1/4 (311 mn)
wide x 8 1/4 (209.5 m)hlgh. 5/8
(16 mn) max. panel thickness.)
Allow clearance i n r e a r f o r infrequent
mi ntenance.
Unit not weatherproof.
Weight approx: 46 l b t . (21 KG).
120 VAC 50760 Hz.
Figure 2-1. Outline and Mounting Dimensions of Model 864
2
Optional Range 1.0.
Optional Remote Range Selection.
I n l e t (Bulkhead f i t t i n g f o r 1/4 (6m)
0.0. tublng) as ordered.
Outlet (Bulkhead f i t t i n g for 1/4 (bmn)
O.D. tubing) as ordered.
Purge I n l e t (Bulkead f i t t i n g f o r 1/8
(3m) O.D. tubing) as ordered.
í.
4
u
I
z
I-
z
8u.
I
e
.
i
r----1
7
0
-I
L
-
/
%
¡
S
f,
-4
f
L
O
.-g
KE
i5
-c
c
E
8
5
?a
.-Emc
8
2
a
ir
3
d
DWG 635325
ALL F L A ñ E
A R R E S I O R A S S f ~ B l l Í SP R O P E R L ? I R S I A L L E D I R
SA1PLE. R t F E R t R C t A I D P U R 6 f I l L E T S A I D
O O l L E I S ( I f USED) AID A L L U l U S E D O P E R l R C S
PLUCCED Y I l R F A C ? O R i IRSIALLED 1ñRÍADED
PLilCS.PROPERLI StCURED I R PLLCE.
LEñS COVER FULLY ERCACED.
*
Figure 2 3 . Outline and Mounting Dimensions of ExploUonProof Madel 865
4
3
Power Consumption
Average, 200 watts; maximum, 5 0 0 watts.
Recorder
Preferably, the recorder should be near enough to the
analyzer and so oriented, that the operator can easily
observe the response to adjustment of the controls. A
10-foot (3 m) recorder output cable is provided as standard.
Recorder connections are diagrammed in Figures 2-4 and
2-5, and are explained in Paragraph 2-9.
2.2 SAMPLE INLET AND OUTLET CONNECTIONS
Sample inlet and outlet connections are shown in Figures
2-1 through 2-3 and are labeled on the anaiyzer enclosure.
NOTE
2.3 CALIBRATION GAS REQUIREMENTS
Analyzer calibration consists of setting a zero point and one
or more upscale points, depending on the number of
operating ranges used.
Aii applications require a zero standard gas to set the
zero point on the meter scale or recorder chart. if the
factory Calibration and Data Sheet specifies the background gas, use it as the zero gas. If background gas is not
specified, use dry nitrogen for the zero gas.
Combined resistance of a current-type recorder and
associated iriterconnection cable must not exceed
2000 ohms for 4 to 20 m A output, or 700 ohms for
10 to 50 mA ourput.
I
2.1.4 UTILITY SPECIFICATIONS
Electrical power requirements are:
Voltage
115 +15volts rms.
Frequency
Either 50 kO.5
Hz or 60 f l . 5 Hz.
Standard Recordrr Output Connections
Recorder Connections for Instrument With
Optional 619458 Iroiitrd Current O u t m o r i d
Voltage Output (+) WHT
Voltage Output
645689
Five-Conduaor
Shielded
Recorder Cable
I
115 115'V rrns
50160 f 0 . 5
Hz
-
$
1-1
v
BLK (SH)
Isolated
i
"m
4
N
2
N
I
Figure 2-4. Electrical Input/OutPut Connections for Model 864 and Generd-Purpou, Model 865
5
Standard Recorder Output Connections
Current Output (-)
Recorder Connections for Instrument With
Optional 619458 Isolated Current Output Board
ij
Voltage Output ( + ) WHT
-+
Voltage Output í-)
BLK
Current Output (+I RED
I
1
Voltage Output ( - ) BLK
v
BLK ISH)
-
v i +
k
GRN
0
4 ' 0
I
NOTE
Electrical installation must comply with requirements of Nationel
Electrical Code (NEC) for Class I , Groups B. C, and D. Division 1
Hazardous Locations, especially Sections 501.4 (a) and 501-5(a).
For convenience of operation, adjustment, and maintenance,
power should be connected through a separate, dedicated switch
approved for the location.
GRN
Power
Cable
115 1 1 5 V rms
50160 +0.5 HZ
CAUTION
Do not operate without lens cover and door securely in place with
all bolts secured, unless area has been determined to be nonhazardous.
HOT
i
1
Figure 2-5. Electrical Inputloutput Connections for Explosion-Proof Model 865.
2.4 SAMPLE HANDLING
Many different sample-handling systems are available. The
type used depends on the requirements of the particular
application and the preferences of the individual user.
Typically, the sample-handling system incorporates such
components as the following: pump; valves to permit
selection of sample, zero standard, or upscale standard gas;
needle valve in sample-inlet line, for flow adjustment;
flow-meter, for flow measurement and/or indication of flow
stoppage; and filter@). to remove particulate matter. On
order, Beckman Industrial Corp., will supply either an
assembly drawing and the set of loose sampling-handling
components required, or a completely assembled system.
2.4.1 LEAK TEST FOR APPLICATIONS INVOLVING
EXPLOSIVE GAS SAMPLES
DANGER
POSSIBLE EXPLOSION HAZARD
If explosive gas samples are introduced into this analyzer.
Beckman Industrial Corporation recommends that sample
containment system fittings and components be thoroughly
leak-checked prior-to initial application of electrical power.
routinely on a periodic basis thereafter. and afier any
maintenance which entails breaking the integrity of the
sample containment system. Leakage of flammable samples
could result in an explosion.
8
Use the leak check procedure appropriate to the specified
pressure limitation of the particular analyzer.
6
Leak Test for Sample Pressures up to 10 psig (69 kPa)
Supply air or inert gas such as nitrogen, at 10 p i g (69 e a ) ,
to analyzer via a flow indicator with range of O to
250 cc/min. Set flow at 125 cc/min.
I
N2
10 psig
(69 k h )
Hug sample outlet; flow reading should drop to zero. if
not, system is leaking. Leakage mmt be corrected before
introduction of flammable sample and/or appiication of
electrical power. Liberaiiy cover ail fittings, seals, and other
possible sources of leakage with suitable leak test liquid
such as SNOOP*(Part 837801). Bubbling or foaming indicates leakage. Checking for bubbles will locate most leaks
but could miss some,as some areas are inaccessible to appiication of SNOOP. For positive assurance that system is
leak-free, use the flow stoppage test.
Leak Test for Sample Pressures over 10 psig (69 @a)
Pressurize the system with air or inert gas such as nitrogen,
making sure not to exceed specified pressure limitation.
Liberally cover all fittings, seals, and other possible sources
of leakage with suitable leak test liquid such as SNOOP*
( Part 837801).Bubbling or foaming indicates leakage, which
must be corrected before introduction of flammable sample
and/or application of electrical power.
T r a d e m a r k of NUPRO Co.. Willoughby,
OH.
J
2.4.2 SAMPLE FLOW RATE
temperature. At extremely high flow rates this may not br
true, but no such effect has been noted up to 18 CFH
(9 L/min).
Flow Rate for Gaseous Samples
For best results, sample flow rate must be in the range of
500 to 1000 cc/min (approximately 1 to 2 SCFH). A
subnormal flow rate will result in undesirable time lag.
Assuming that two cell volumes are required to flush any
cell, the table at right indicates approximate flushing time
at atmospheric sampling pressure, i.e., the outlet o f the cell
venting to atmosphere. General-purpose and explosionproof housings have different inlet tube volumes; thus the
corresponding total volumes and flushing times are
tabulated separately.
Flushing time is inversely proportional to flow rate and
directly proportional to sample cell pressure. At elevated
sample pressure, recommended flow rate is increased.
For example, at 200 psig (1380 kPa) sampling pressure,
recommended flow rate is 18 CFH (9 L/min).
The primary effect of flow rate other than flushing time
is cell pressure. Due to the restriction of the exit tubulation, increasing flow rate increases sample pressure in the
cell. For a 13?4-inch (343 mm) cell venting to atmosphere,
the cell pressure rises from O psig (O kpa) at no flow,
essentially linearity, by 1 mm Hg per CFH flow up to at
least 20 CFH (10 L/min).
At 7.5 to 8.0 CFH (3.8 to 4 L/min), therefore, the
pressure is increased by about 1% and the output signal is
thereby increased by about the same 1% over static conditions. In a i l cases, the effect of pressure on readout is
eliminated if the same flow rate is used for the measured
sample as for the standard gas.
It should be noted that at higher flow rate, because of
increase in sample -cell-pressure, the nonlinearity o f the
calibration curve increases. “lierefore, if higher flow rates
are required, the calibration curve should be redrawn at
these same flow rates.
At 2 CFH (1 L/min) gaseous sample temperatures are
equilibrated to instrument temperature regardless of stream
I
CELL LENGTH
mm
.O39
2.5 STACKED SAhlPLE CELLS
For applications where the concentration of the measured
component varies greatly, necessitating greater instrument
rangeability, the analyzer may incorporate fwo sample ccb,
one short and the other long. These are “stacked” in series,
forming two analysis chambers separated by an optical
window as shown in Figure 26. The short cell is used for
:malysis of the higher concentration ranges; the long cell is
used for analysis of the low concentration ranges. The two
cells cannot be used for simultaneous analysis of the high
and low ranges. U W e one cell is being used for analysis and
is therefore receiving a flow of sample or calibration gas,
the unused cell must be purged with nitrogen or other
(appropriatebackground gas.
MAMPLE
The following ranges can be combined in one analyzer by
stacking a 13ih-inch (343 mrn) cell and a 4 mm cell:
O to 200 parts-per-millionCO by volume in the 13%-inch
(343 mm) cell; and
O to 15% CO by volume in the 4 mm cell.
The recommended flow system is shown in Figure 24.
TOTAL VOLUME
(CELL+ INLET TUBE)
CELL VOLUME IN a
(Without lnla Tube) GENERAL PURPOSE EXPLOSION PROOF
IINCHES
I
1
I
I
Flow Rate for Liquid Samples
If liquid sample temperature is much higher or much lower
than sample cell temperature, a maximum recommended
flow rate is 15 cc/min. If on the other hand, sample temperature is controlled close to instrument temperature before
entering, flow may be increased to 150 to 200 cc/min. In
the former case, with a 1 mrn thick sample cell, flushing
takes approximately sixty seconds, wliiie in the latter case
it takes only about five seconds.
I
0.28
1
I
12 cc
1
I
I
4cc
I
TIME FOR TWO VOLUMES AT 2 SCFH
(1 L h i n i 8t 760 mmHg (101 kPd
GENERAL PURPOSE
I
2 sec
] EXPLOSION PROOF
I
i
3
.118
O .85
12 cc
4cc
2 sec
0.5 sac
4
.157
1.14
12 cc
4 cc
2 sec
0.5 sec
8
.315
2.28
13cc
5 cc
2 sec
la
16
.630
4.56
16 cc
8 cc
2%
1 sec
9.12
2occ
12cc
3 sec
2sM
18.24
25 cc
21 cc
3%
3 SO(:
5.03
36.48
44 cc
40 cc
6 MC
5 sac
69 cc
9 sec
9SOC
32
1.25
64
I
128
2.52
I
9.13
66.12
73 cc
343
13.50
97.76
105 cc
101 u:
13 ME
13sec
381
15.00
108.60
116cc
112cc
15 KC
14 sec
232
h
I
0.5 wc
I
~
.
*
7
J
m
--
N2 Purge
Optical
Window
Sample 1
Sample 2
A * Long Sample Cell
E = Short Sample Cell
VI
FI1
FI2
v2,3,4,5
= Four-Way Valve
= Flow Control Valve
= Flow Control Valve
= Shutoff Valves
Upscale 1
Upscale 2
Figure 2-6. Typical Flow Diagram for Stacked Cell Configuration
2.6 DIFFERENTIAL ANALYSIS WITH FLOWTHROUGH REFERENCE CELL
In some applications, the analyzer is used to measure the
difference between the concentration of the component of
interest in two sample streams. If so, the reference side of
the analyzer, as well as the sample side, utilizes a flowthrough cell. The sample cell receives the sample stream
which contains the higher concentration of the component
of interest. The reference cell receives the stream containing
the lower concentration of this component.
The ceil spacing is factory-set for the particular appiication. Typical settings range from 0.005-inch (0.127 mm) to
0.025-inch (0.635 mm). Cell spacing is adjusted with a
special wrench provided. First, the barrel is rotated clockwise into the body until the stop is reached.
2.7 LIQUID SAMPLE CELLS
If ordered for analysis of liquid samples, the analyzer
incorporates the 641488 Variable Pathlength Liquid C d
Assembly, which provides micrometer adjustment of cell
spacing or pathiength. Construction of this special cell
assembly is shown in a drawing included in the Parts Est,
Section Eight.
Basically, the sample cell consists of body and barrel
sections, each containing optical windows at the ends of the
cell. Within the stationary body section, the barrel section'
can be rotated by means of micrometer-guided threading.
One full turn advances the barrel 0.025-inch (0.635 mm).
The cell barrel is notched in five parts to obtain accurate
increments of 0.005-inch (0.127 mm).
At the stop position, cell spacing is essentially zero. One
full turn counterclockwise from this position creates a ceii
spacing of 0.025-inch (0.635 mm).
8
C4 KUON
Do nor exerr force at rhe srop position as this could
cause damage to the optics.
Applications
,
Typical applications are:
Water in Acetone, O to 1% up to O to 20%.
Water in Methanol, O to 1% up to O to 20%.
Water in Ethanol, O to 1% up to O to 20%.
Oil in Carbon Tetrachloride arid Freon 113, up to O to 10
parts-per-miilion.
Acetic Acid in Acetic Anhydride.
Water in Dimethyl Formamide.
NOTE
The tnusiriiurn floiv rate tlirnicgh the sample cell is
20 cdrnin. This ir! order to obtuiri fust response, the
rnujor portiori of the suriiple should be bypassed.
Paragraphs 2.8 through 2.12, following, cover features
which may be selected for your particular needs and
applications.
2.8 ELECTRONIC RESPONSE TIME SELECTION
The desired electronic response time is selected on the
638490 D.C. Amplifier Boqrd as shown in Figure 3-3.
Standard factory setting is one second.
2.9 RECORDER CABLE CONNECTIONS
If a recorder, controller, or other output device is used,
connect it to the analyzer with the shielded threeconductor cable provided. See Figure 2-4 or Figure 2-5.
If the analyzer provides a voltage output, connect the
white (t) and black (-)leads to the output device.
If the analyzer provides a current output, connect the
red (+) and white (-) leads to the output device.
Combined resistance of a current-type recorder and
associated interconnection cable must not exceed
2000 ohms for 4 to 20 mA output, or 700 ohms for
20 to 50 mA output.
2.1 2 PURGE CONNECTIONS AND REQUIRMENTS
FOR GENERALPURPOSE MODEL 864/865
If required for safety, the General-Purpose Model 864/865
may be equipped for purging through installation of the
630951 Purge Kit, consisting of a purge fitting plus associated gasket, screws, and washers. The analyzer may then be
purged with clean, dry air or suitable inert gas. The kit,
when installed dong with user-provided pressure or flow
indicator, is designed to meet National Fue Protection
Association (NFPA) Standard 496-1974 for Type Z air
purge. The kit, instailed as described in the instructions, is
designed to reduce the classification within the enclosure
f r o m Division 2 (normally non-hazardous) to nonhazardous. Refer to Instructions 015482307, provided.
Also, see CAUTION note Paragraph 2.13.1
If the original cable is replaced with a different cable,
connect the replacement cable to TBl as shown in Figure
2-4or Figure 2-5.
DANGER
POSSIBLE EXPLOSION HAZARD
NOTE
2.10 646093 RANGE I.D. CABLE ASSEMBLY (Optional)
The 656093 Range I.D. Cable Assembly provides contact
closure signals that enable a computer or other external
device to determine the range manually selected with
front-panel RANGE Switch SWl . The cable is connected to
RANGE Switch SW1 and extends to connector J10,
mounted on the rear of the case.
The pin-out connections of J10 are as follows:
P i n A ..................................... TUNE
PinB ...................................
Range1
PinC ................................... Range2
Pin D ...................................
Range3
Pin E .....................
COMMON (Switch Wiper)
1
the addition of a relay board with its own power supply
connected to the Range Switch (Sl) and extending t o the
rear of the case to connector (Jll).
The pin-out connections of J11 are as follows:
P i n A ...................................
Range1
PinB ...................................
Range2
PinC ...................................
Range3
Pin E ....................
.Extemal Voltage Available
(+12 VDC at 100 mA)
PinF ............................
CommonGround
This system is set up for ground closure switching
between Pin F and the appropriate pin of A through C.
2.1 1 646095 REMOTE RANGE KIT (Optional)
The 646095 Remote Range Kit permits the remote selection o f operating range via contact closure signals applied
by the computer or other device. This is accomplished by
This analyzer is the typefrequently utilizedfor the analysis
of explosive gases. If used for such gases, Beckman
Industrial Cop. recommends that it be contained in an
explosion-proof housing. NFPA 496, ISA S12-4 and other
similar United States and international standords rehting
to purging are directed only to the invasion of explosive
gases into the analyzer housing from the outside atmosphere. These standards do not address the abnormal
release of explosive gases intentionally introduced into the
analyzer housing. There are no recognized stan&&
addressing such potential hazard.
If explosive gases are introduced into this anakyzer,
whether or not it is contained within the explosion-proof
housing, Beckman Industrial Cop. recommends that the
- carefully leak-checked
sample containment system k
upon installation and before initial startup, during routine
maintenance and any time the integrity of the sample
containment system is broken to ensure the system is in
leak-proof condition. Leak-check instructions are provided in Paragraph 2.4.1.
9
'
2.13 OPTIONAL PURGE KIT FOR
EXPLOSION-PROOF MODEL 865
Purging of the enclosure of the Explosion-Proof Model 865
with air or inert gas may be recommended in some applications to provide a corrosion-free or spectrally-constant
internal atmosphere. The purge is not intended to provide
explosion hazard protection. Both the purge inlet and
outlet fittings must be equipped with 638426 Flame
Arrestor Assemblies.
2.14 ELECTRICAL POWER CONNECTION
2.14.1 MODEL 864 AND GENERALPURPOSE
MODEL 865
Connect analyzer power cord to a grounded a.c. source of
115 +15 V mis, 50/60 kO.5 Hz. See Figure 2-4. if power
receptacle does not have third (ground) contact, use an
adapter to provide proper grounding.
C4 üTiON
I
Cc
E
t
c
G
i f analyzer is equipped with Type Z air purge per NFPA
496-19 74 (see Paragraph 2.12) and is insralled in a class I,
Division 2, location, and the power cord is not replaced by
conduit wiring, the following precautions must be taken:
1. Replace power cord with a locking andgrounding type
Plug.
2. Permanently mark lockiiig and grounding type recep
tacle as follows:
“WARNING: DO NOT CONNECT OR DlSCVNNEíT ANALYZER UNDER LOAD UNLESSARU
IS KNOWN TO BE NON-HAZARDOUS. ’*
3. Rovide power isolation switch, suitably protected for
the location.
Purge Outlet Fining
Accepts 1 /4-inch (6.35 mm)O.D. Tube
Figure 2-7. Air Purge Installation for Explosion-Proof Model 865
htailation and Operation
Connect inlet to a supply of clean, dry, air or suitable inert
gas as shown in Figure 2-7. Recommended supply pressure
is 5 psig (34.5 e a ) . This provides a flow rate of approximately 20 cubic feet-perhour (approximately 10 liters-perminute) and an internal case pressure of approximately
8 inches of water (approximately 2 Ha). With a flow of
20 scfh (10 liters/minute), approximately 4 case volumes
of purge gas flow through the case in thirty minutes.
A 1/4-inch (6.35 mm) 0.d. tube, maximum length
15 feet (4.5 m), may be connected to the purge outlet if
required.
See Figure 2-3 for additional details and for precautions
to observe in installation and operation of explosion-proof
enclosure.
10
2.14.2 EXPLOSION-PROOF MODEL 865
The Explosion-Proof Model 865 must be wired to a source
of 115 115 V rms,50/60 kO.5 Hz power in accordance with
the requirements of National Electrical Code, Sections
501-4 (a) and 501-5 (a) by way of an approved switch
dedicated to the Model 865. See Figure 2-5.
4
SECTION THREE
STARTUP
DANGER
POSSIBLE EXPLOSION HAZARD
If explosive gas saniples are introduced into this analyzer,
Reckman Industrial Corporation recommends that snmple
contairimrnt system fittings and components be thoroughly
leak-checked prior to initial application of electrical power,
routinely on a periodic basis thereafter, and after any maintenutice mhich entails breaking the integrity of the sample
coníainment system. Leakage offlammable samples could resuii
in an explosion. Refer to Paragraph 2.4.1
Figures 3-1 and 3-2 give locations and brief descriptions
of analyzer controls and adjustments. Figures 3-3,34, and
3-5 provide similar information for controls and adjustments on the 638490 D.C. Amplifier Board, the optional
630153 Current Output Board, and the optional 619458
Isolated Current Output Board, respectively. Preparatory to
startup and operation, a thorough familiarization with these
figures is recommended. For more detailed information on
control functions, refer to Section Five.
3.1 DETAILED STARTUP AND CALIBRATION
PROCEDURE
During final factory checkout before shipment, analyzer
adjustment settings were properly established. Preparatory
to initial operation, the analyzer will normally require only
a check of zero and gain settings per the CONDENSED
STARTUP AND STANDARDIZATION PROCEDURE at
the front of the manual. It should then provide satisfactory
operation.
If operatian is iinsatisfactoy, alignment of the optical
bench has probably been disturbed, necessitating use o f the
following detailed calibration procedure.
1. With power off, or meter shorted, verify that front-panel
meter reads zero. If not, adjust Meter Mechanical Zero
Screw for zero reading.
2. Apply power or remove short from meter. Turn RANGE
Switch to position 1.Allow analyzer to warm up for at
least one hour, and preferably for eight hours. Instrument is operable immediately after connection to a.c.
power, but drifts at f m t and requires one hour to
equilibrate. if instrument is used sooner, readings must
be taken immediately after the initial calibration, and
recalibration is recommended immediately before
subsequent additional readings.
3. Check oscillator tuning:
a. Turn RANGE Switch to TUNE.
b. If instrument has been in routine operation, compare
present meter reading with previous readings obtained
in TUNE mode. Present and past readings should
agree to within a few of the smallest scale divisions; if
so, oscillator is properly tuned; review Figures 3-1
through 3 4 , then proceed directly to Step 4.
If analyzer her not yet been in operation, or if
reading in TUNE mode is not within the acceptable
limits, tune oscillator per Steps 3c through 3e,
following.
C. Insert a thin-bladed screwdriver through the hole
marked OSC TUNE, through the cardboard guide
tube, and into the slot o f the adjustment screw.
Adjust screw for peak reading on meter.
NOTE
Certain high-sensitivity iiisttuments, such m O to 50
or O to 100 ppm CO, do not utilize screwdriver
adjustment of oscillator tuning, even though the hole
marked OSC TUNE is present in the front panel. In
these instruments, the oscillator tuning adjmtment
shaft has a small knob, accessible to the fingers by
reaching behind the front panel. in these instruments,
the entire optical system is slightly elevated on a
shock-mounted plate to minimize response to vibration; thus the oscillator tuning shaft is positioned
slightly above the OSC TUNE hole.
d. Turn OSC TUNE Adjustment counterclockwise untii
meter reading decreases to between 70% and 75% of
the maximum obtainable value noted in Step 3c.
Oscillator is now properly tuned.
e. Return RANGE Switch to position 1.
4. Turn on recorder, if provided. It wiii yield better
accuracy than the *l% of fullscale obtainable with the
front-panel meter. Recorder, if available, should therefore be used for all readings during subsequent calibration and analysis.
5. Check Bias Adjustment: .
NOTE
Component electronic offsets will shift slightly as the
interior temperature of the instrument changes. For
this reason it is recommended that, immediately prior
to adjustment of the Bias Controls, the instrument be
allowed to run with cabinet closed for at least several
hours (or long enough for the instrument to reach its
regulated operatiw temperature). If subsequently
bias level drifrs siightly, comer instrument operation
and readings Win still be obtained The only effect will
be the introduction of a small interaction between
the ZERO and C A N Controls.
a. Set CAiN Control at counterclockwise limit to
remove ail signal from input of amplifier circuitry. In
the General-Purpose Model 864/865,the Duodial on
the GAIN Control wili read 0.00 at this setting.
b. Set ZERO Control at clockwise limit to remove aü
compensation for n o d optical offset signai. in the
General-Purpose Model 864/865,the Duodiai on the
ZERO Control wili read 10.00 at this setting.
C. Set Switch SW3 on 638490 D.C. Amplifier Board,
Figure 3-3,t o RUN.
d. Set RANGE Switch to the highest sensitivity ranp
that w
i
l
lbe used during operation.
e. Adjust Coarse Bias Control R33 on 638490 D.C.
Amplifer Board until meter or recorder reads 50%of
fullscale, or, if this is unobtainable, until maximum
reading is obtained.
11
e
aa
I
.
.-I
a
Y
z
_-
d
$1
i
uuum!w
c
1
Motor/Source
2. Source
1. Optical Shutters
Assembly
Vertical
3. MotorlSource Assembly
Mounting Screw
Long Cell Hold-Down Screw
I B
Reference Cell*
Detector
GENERALPURPOSE MODEL 864/865
i
/
/
,
I
-
MotorlSource
Assembly
1. Optical Shutters
Source Voltage Adjustment
3. MotorlSource Assembly
Mounting Screw
Long Cell Hold-Dow
Detector
EXPLOSIONPROOF MODEL 866
*ifoptical pathlength i s less than 32 mm, sample and reference cells consist of a single cell block with two prallel holes bored
through.
**Reference cell should be rotated so orientation of desiccant holder i s appropriate to type of desiccant. With Cardoxide (COZ
measurement), holder should be vertical. With all other desiccants, holder should slant downward below the horizontal.
FUNCTION
ADJUSTMENT
Provide coarse optical balance adjustment, used if acceptable balance is unobtainable with
frontpanel SOURCE BALANCE Adjustment, or is obtained near the clockwise limit of this
control. Shutters are sliding metal plates attached to entrance ends of sample and reference
cells, permitting partial blocking of either beam, as required t o obtain balance.
2. Source Assembly Vertical
Positioning Adjustment
(Outof-Phase Adjustment)
Refer to Paragraph 3.1,
, Step 6.
3. MotorlSource Assembly
Mounting Screws
Used for optical alignment of source assembly, t o minimize outofphase Signal. With sample
and reference beams clear, Vertical Positioning Screw is rotated t o move source assembly up or
down, as required t o minimize the meter reading. If Vertical Positioning Screw is difficult t o
rotate, very slightly loosen the two retaining screws. After adjustment of Vertical Positioning
Screw, retighten retaining screws t o secure sources t o MotorlSource Assembly.
Chassis has several alternative sets of tapped holes to receive these mounting screws. This
arrangement permits moving the Motor/Source Assembly backward or forward toaccommodate
cells of various lengths.
Used t o set the voltage applied t o the two sources. Nominal setting ir 30 volts a.c. NOTE: In
General-Purpose Model 864/865,Source Voltage Adjustment i s external; see Figure 3-1.
1;
Figure 3-2. Internal Adjustments of Model 864/865
13
3. Slide Switch SW3
I
2. Jumper which
Bypasses R23
I
1 . Switch SWl
(Electronic Response
Time Selection Function)
Meter Calibration Adjustment
Potentiometer R15
Range 2 Gain Adjustment
Potentiometer R 9
Range 3 Gain Adjustment
Potentiometer R13
Coarse Bias Adjustment
Potentiometer R33
Fine Bias Adjustment
Potentiometer R34
Voltage Output Jumper
1
I
......
'
Connect Voltmeter from this
Point t o Ground t o Meaaure
Output from AR2 Pin 6
L 5. Slide Switch SW2
4. Switch SWl (Voltage Output Selection Function)
1
I
FUNCTION
CONTROL
~~~~~~
1.Switch SW1 (Electronic Response Time
Selection Function)
-
2. Jumper which Bypasses
R23.
~~
-
-he desired electronic response time is obtained by selection of the appropriate combination of settings on
he specified switch contacts,as given in the following table.
IOTE: Time values (1,3,and 9) are number of seconds t o 90% of final reading.
Used to select desired sensitivity for frontpanel ZERO Control. With jumper clipped out, control of ZERO ir
five times finer than when jumper is connected. Removal of the jumper wi!l necessitate readjustment of Bias
Potentiometers R33 and R34. Items 8 and 7.
~~
3. Slide Switch SW3
RUN is normal operating position. CAL position is used only during calibration of the optional 633756
Linearizer Board. Selection of CAL position grounds the input t o the DC Amplifier Board, and reverses the
Dolaritv of the front-panel ZERO Control.
4. Switch SW1 (Voltage
The desired voltage output is obtained by placing the corresponding one of four switch contacts in ON
position. The other three contacts must be in OFF position. Outputs provided are .OlV, .1V, and 5V.
output Selection
Functionl
5. Slide Switch SW2
6. Voltage Output Jumper
These two items used in combination to provide the internal signal routing appropriate to the desired type of
output.
For standard, non-linearized. potentiometeric output, place SW2 at position "€.I" and verify that jumper
is connected.
For current output, if analyzer is so equipped, place sW2 at "E.1" and clip jumper, if present.
For optional linearized potentiometric output, if analyzer is so equipped, place SW2 at " L I N and verify
that jumper has been removed.
7. Fine Bias Adjustment
Potentiometer R34
Used in combination t o null out component electronic offsets. With GAIN Control at counterclockwise limit,
ZERO Control at clockwise limit, and RANGE Switch at position 3 , R33 is adjusted t o center the span of
R34 near the required near-ground d.c. level. Then, R33 is adjusted for approximate zero reading on meter or
recorder. Finally, R34 ir adjusted for exact zero reading.
~~
8. Coarse Bias Adjustment
Potentiometer R33
9. Ranga 3 Gain Adjustment
Potentiometer R13
Used t o set upscale calibration point for Range 3 (after Range 1 calibration completed, with analyzer now
receiving an upscale standard gas appropriate t o Range 311 Range 3 gain i s adjustable from 2X t o 1OX tho
Ranae 1 -in.
10. Range 2 Gain Adjustmen
Used t o set upscale calibration point for Range 2 (after Range 1 calibration completed, with analyzer nom
receiving an upscale standard gas appropriate t o Range 21. Range 2 gain is adjustable from 1X to 3.5X tha
Ran- 1 aain.
Potentiometer R 9
~~
11. Meter Calibration Adjust
ment Potentiometer R15
~~
Used t o make meter agree with recorder. With recorder reading 100%. R 15 is adjusted so meter reads 1 OO.
Figure 3 3 . Controls and Adjustments on D.C. Amplifier Boerd
14
f. Adjust Fine Bias Control R34 on 638490 D.C.
Amplifier Board back and forth to find extremes to
which meter or recorder can be varied with R34. (If
meter goes offscale, consider end o f scale to be the
extreme.) Then, set R34 so meter reads approximately midway between these extremes.
g. Readjust Coarse Bias Control R33 until meter reads
approximately zero. Readjust Fine Bias Control R34
so meter or recorder reads exactly zero.
h. Turn RANGE Switch back and forth between
position used above and position 1. When instrument
is properly biased, meter or recorder reading will not
change when RANGE is changed.
I
1. M A OUTPUT Selector Switch
I
2. Zero Current Adjustment
Potentiometer
3. SPAN Adjustment R30
1 . Switch SW1
I
2. ZERO Adjustment R19
I
4-20
10-50
M.A.
OUTPUT
1
R4
I
-
-~
~
~
CONTROL
FUNCTION
1. Switch SW1
NORM Position. Used for instrumen
without 619452 Linearizer Board.
LIN Position. Used for instrumentwitl
one or more 619452 Linearize
Boards.
1. MA OUTPUT
Selector Switch
Provides selectable output oí 4 to 2C
or 10 to 50 milliamperes for a current
type output device.
2. Zero Adjustment
R19
3.SPAN Adjustment
R30
Figure 3-4.Controls and Adjustments on 630153 Current Output
Board (Optional)
io establish lower Ima of cur
rent output at 4 mA.
Used
I
Used to establish upper limit of cur
rent output at 20 mA.
Figure 36. Controls and Adjustments of 619458 Isolated Current
Output Board (Optional 619454 Isolated Current
Ourput Kit)
--- - x d
1
6. SOURCE BALANCE Adjustment:
a. Warm up analyzer for at least one hour, and preferably for 24 hours.
b. With RANGE Switch at TUNE,adjust OSC TUNE for
peak reading on front-panel meter. Then, turn
counterclockwise until meter reading decreases to
75% of peak value.
c. Pass nitrogen or selected zero standard gas through
the analyzer. (If analyzer is used for differential
analysis, and is therefore equipped with a j i o w
through reference cell, the sample and reference celis
must now receive the same standard gas.
d. Set RANGE Switch at position 3.
e. Turn GAIN Control to counterclockwise h i t .
f. Turn ZERO Control to clockwise limit. Meter should
now read zero; if not, check bias adjustment (R33
and R34).
g. Turn SOURCE BALANCE Control to counterclockwise limit.
h. Move RANGE Switch to position 1.
i. Move both optical shutters, Figure 3-2, completely
out of the associated beams.
j. increase setting on GAIN Control until meter or
recorder reads between 50% and 100%of fullscale.
k. Determine which of the two optical shutters causes a
downscale deflection when moved into the associated
beam.
1. Adjust the selected shutter for minimum obtainable
reading on meter or recorder. Leave the other shutter
completely out of the associated beam.
m. Rotate Vertical Positioning Screw on top of Motor/
Source Assembly to minimize reading of meter or
recorder.
NOTE
If Vertical Positioning Screw is difficult to rotate,
very slightly loosen source retaining screws, Figure
3-2. In some instruments, an offset screwdriver will
be required. After completing adjustment of Vertical
Position Screw, retighten retaining screws so sources
are secure to MotorlSource Assembly. A loose source
assembly will cause electronic noise.
Repeat Steps 61 and 6m with GAIN Control set at 500
or higher. if it appears that the final operating gain
required for a fillscale deflection w
i
l
lbe much greater
than 5 0 0 , repeat Steps 6j and 6k at the actual operating
gain setting.
16
n. Turn SOURCE BALANCE Adjustment 1/2 to 3/4 of
a turn clockwise.
O. As a final check, very slowly insert a card into the
sample beam, taking care not to drive the meter offscale. As this is done, the reading on the meter or
recorder should move continuously upscale.
Next, very slowly insert the card into the refererlce
beam. The reading should first move slightly downscale, and should then move upscale.
3.2 CHECKING INTERFERING COMPONENTS
OF THE SAMPLE STREAM
Some sample streams contain, in addition to the component of interest, various other infrared-absorbing substances. To minimize interference in such applications, the
instrument may incorporate an optical fdter and also, if
necessary, a sealed filter cell containing an appropriate gas
charge, as noted in the Factory Calibration and Data Sheet.
WAW I N G
Certain applications use a special high-pressure gas
filter cell, permanently sealed, and bearing a label
that warns against opening. Do not attempt to
recharge these cells.
If so ordered, the Infrared Analyzer and associated
sample-handling system are factory-assembled on the basis
of customer-supplied information entered on a standard
Beckman Industrial Corp. Application Data Analysis form,
available on request. Data requested include a complete
analysis of the sample stream, and the normal range of
concentration for each component. If the instrument
functions properly with the zero and upscale standard gases
but not with the sample stream, first check the composition
of the stream and review any other suspected sampling
problems.
For applications involving interfering components, the
Factory Calibration and Data Sheet may indicate the interference factors. If a check on interference effects is desired,
admit to the instrument a series of test samples, each
containing the maximum expected concentration of a
particular interfering component. Be sure that the test
samples do not contain any of the measured component;
e.g., CO in a stream being analyzed for CO. Compare the
readings thus obtained with the corresponding values from
the Factory Calibration and Data Sheet. Failure of the
experimentally obtained readings t o agree with the listed
values may be indicative of a leaky detector, faulty optical
filter, or trace amounts of the measured component in the
interferent test blend.
SECTION FOUR
OPERATION
4.1 ROUTINE OPERATION
First perform CONDENSED STARTUP AND STANDARD
lZATION PROCEDURE given at the front o f manual.
Tlien, set RANGE Switch for desired operating range: 1,2,
or 3. Pass sample gas through instrument; it will now
automatically and continuously analyze the sample stream.
With standard (non-linearized) potentiometric output, or
optional current output, use calibration curve at rear of this
manual to convert meter or recorder readings into concentrations o f the measured component. However, i f the
analyzer is equipped with a linearizer circuit board adjusted
for the particular operating range, the calibration curve is
not required.
As a check on instrumént performance, it is recommended that the operator keep a daily log o f the CAIN
Control setting. Refer to Paragraph 6.2
4.2 RECOMMENDED CALIBRATION FREQUENCY
For optimum accuracy, the instrument must be calibrated
frequently. Maximum permissible interval between calibrations depends on the analytical accuracy required, and
cannot therefore be specified. It is recommended that
initially the instrument be calibrated once every eight (8)
hours, and that this practice be continued until experience
indicates that some other interval is more appropdate.
If routine upscale calibration is performed with the
optional Gasless Calibrator Accessory, note that the simulated concentration value used for the optical window is
valid only for operation at a particular atmospheric pressure. A change in pressure o f 1inch of mercury (3.38 kPa)
d result in a readout error o f approximately 3% o f fullscale. Therefore, i f barometric pressure changes significantly it is advisable to recheck the calibration against an
upscale standard gas.
4.3 SHUTDOWN
Normally, instrument power is left on at aíi times except
during a prolonged shutdown. Following shutdown, repeat
CONDENSED STARTUP AND STANDARDIZATION
PROCEDURE to restore instrument to service.
S E CTION FIVE
I N S T R U M E N T THEORY
Paragraph 5.1 explains the functioning of the detection
system. Paragraph 5.2 describes the electronic circuitry.
Infrared Source
5.1 DETECTION SYSTEM
As shown in Figure 5-1, the analyzer produces infrared
radiation from two separate energy sources. Once produced, this radiation is beamed separately through a
chopper which interrupts it at 10 Hz. Depending on the
application, the radiation may then pass through optical
fifters to reduce background interference from other
infrared-absorbingcomponents.
The infrared beams pass through two cells; one a reference ceil containing a nonbabsorbing background gas, the
other a sample cell containing a continuous flowing sample.
During operation, a portion o f the infrared radiation is
absorbed by the component o f interest in the sample, with
the percentage of infrared radiation absorbed being proportional to the component concentration. The detector is
a “gas microphone” on the Luft principle. It converts the
difference in energy between sample and reference cells to a
capacitance change. lliis capacitance change, equivalent to
component concentration, is amplified and indicated on
a meter, and if desired, used to drive a recorder and/or
controller.
5.2 ELECTRONIC CIRCUITRY
The block diagram of Figure 5-2 traces the signal through
the electronic circuitry and depicts the various waveforms
involved. For a more detailed picture of the circuitry, refer
to schematic wiring diagram of Figure 9-1,and to appropriate pictorial wiring diagram: Figure 9-2,Model 864;
Figure 9-3,General-F’urpose Model 865; or Figure 9-4,
Explosion-Proof Model 865. Details of plug-in circuit
boards and other individual circuits are shown in separate
schematic diagrams, as referenced in Figures 9-1 through
9-4.
5.2.1 633296 OSCILLATOR CIRCUIT BOARD AND
ASSOCIATED ELEMENTS OF
AMPLITUDE-MODULATION CIRCUIT
in the 633296 Oscillator Circuit Board, Figure 9-5,the
10 MHz carrier wave is generated by a crystalcontrolled
radio-frequency oscillator using crystal Y1 and transistors
Ql andQ2.
The modulation circuit is driven by the detector, the
sensing element of the analyzer. Mechanical functioning of
the detector is explained in Paragraph 5.1. Considered
electronically, the detector is a two-plate variable capacitor.
The modulator is coupled inductively, through one winding
of inductance L1, to the osciüator. Amplitude of the 10
MHz carrier thus varies with the 10-Hz modulating signal.
Detector
Recorder
Signal
Circuitry
Component of Interest
0 Other Molrcules
Figure 5-1. Functional Diagram of Detection System
The following paragraphs consider functioning of the
modulation circuit in greater detail. As shown in Figure 5-3,
A, the detector and one winding of inductance L1 constitute a tank circuit. Both circuit elements are variable:
1. During tuning, inductance is changed by manual rotation
of the OSC TUNE! Adjustment, which moves a metallic
slug in the core of Ll.
2. During operation, capacitance of the detector changes
continuously as the diaphragm is displaced. The
resultant variations in capacitative and inductive
reactance change the impedance of the tank circuit with
respect to the fured-frequency carrier wave.
Resonant frequency =
for the tank circuit
1
2~~
Where
L = inductance of the winding on L1
C = capacitance of the detector
c
18
I
A P A LA d
p‘
$ERVIClOS DOCUMENTALES
zT
Functioning of hlodulation System in TUNE Mode
Preparatory to oscillator tuning, the RANGE Switch is
placed in TUNE position, to connect the electronic
circuitry in a configuration shown in the functional diagram
o f Figure 5.3, A. In this mode, the meter indicates the rms
value of the halfwave-rectified carrier. Tlie tank circuit is
now adjusted in the following two-step sequence.
Tttning: Initially, the OSC TUNE Adjustment is set
somewhat counterclockwise from its correct setting.
Then, it is rotated clockwise to move the slug into the
core, thus iwreasirig inductance and decreasing resonant
frequency. The adjustment is set for maximum obtainable meter reading. At this setting, tankcircuit resonant
frequency is the same a s oscillator frequency (i.e.,
nominal 10 MHz). See Resonance Curve Number 1,
Figure 5-3, B.
L,
. Defrtning: By counterclockwise rotation of the OSC
TUNE Adjustment, the slug is partially withdrawn from
the core, thus decreasirig inductance and increasing
resonant frequency. The adjustment is set so meter
reading decreases to between 70% and 75% of the
maximum obtainable value noted in Step 1, above. See
Resonance Curve Number 2, Figure 5-3, B. This curve
has the same shape as that obtained in Step 1,immediately preceding, but is displaced to the right.
Functioning of Modulation Sjwem in Operating Mode
)+
After tuning is completed, the RANGE Switch should be
moved to position 1 to place the zero and calibration
circuitry in operation. In this mode, the meter indicates the
amplitude of the IO-Hz detector-output signaL Overall
sensitivity of the analyzer system may now be checked by
blocking the sample beam to simulate total absorption of
sample-beam energy and thus provide the maximum obtainable IO-Hz detector-output signal. During that portion of
the chopping cycle while the chopper is unblocking the
sample and reference beams, the diaphragm distends away:
from the metal button, thus decreasing detector capacitance and shifting the tankcircuit resonance curve to the
right. At the moment the diaphragm reaches maximum
distention, the curve reaches the position of Curve 3, Figure
5-3, B.
Assume that the analyzer is now placed in normal operation by removing the blockage from the sample beam and
passing sample gas through the sample cell. The diaphragm
now pulses cyclically, causing the resonance curve to move
continuously back and forth within the limits defined by
Curves 2 and 3 of Figure 5-3,B. Carrier amplitude decreases
as the curve moves to the right, and increases as it moves to
the left. Thus, the response characteristics of the system
depend on the location of Curve 2. Position of this curve
depends on the degree of tank-circuit detuning used.
Advantages o f operating on the portion of ihe curve
obtained by detuning to 70% to 75% of the maximum
obtainable carrier amplitude are: maximum slope yields
highest sensitivity; minimum curvature provides best
linearity.
Radio-Frequency Demodulator
The amplitude-modulated 10 MHz carrier from the
detector/oscillator circuit is applied to the radio-frequency
demodulator. T h i s circuit is a voltage-doubler type rectifier
utilizing diodes C R l , CR2, CR3, and CR4; and capacitor
C7. The circuit gives approximately double the output
voltage o f a conventional halfwave rectifier. This result is
obtained by charging a capacitor during the normally
wasted Iialf-cycle, and then discharging it in series with the
output voltage during the next half-cycle.
5.2.2 633290 or 635785 FILTER/RECiiFIER BOARD
AND ASSOCIATED ELEMENTS
The Filter/Rectifier Board is supplied under two Part
Numbers: 633290. for General-Purpose Model 864/865.
and. 635785, for Explosion-Proof Model 865. Electronically, the two boards are identical; physically. they differ only
in the orientation of trimming potentiometers R i
6. RZ 1 ,
and R30. In the General-Purpose Model 864’865. these
potentiometers are accessible from the side. I n the Explosion-Proof Model 865, they are accessible from the top.
Within the Filter/Rectifier Board. Figure 9-6 or 9-7. the
signal passes in turn through the following stages:
1. Buffer Ampfifier. The signal from the detector/
oscillator combination is applied to a buffer amplifier
utilizing transistors 43 and Q4.The output signal from
the buffer amplifier is applied to front-panel GAIN
Control R4. This potentiometer changes the gain of the
overail system by adjustable attenuation o f the signal
applied to the 10 Hz bandpass filter, item 2.
2. IO Hz Bundpas F17ter. This active filter, utilizing
operational amplifier A R I , discriminates against all
frequencies other than the IO Hz chopping frequency.
The resultant clean 10 Hz signal, with undesired frequencies filtered out, is observable by connecting an
oscilioscope to TP2 YFiL Filter Pass Adjustment
potentiometer R16 is adjusted for maximum amplitude
of the 10 Hz signai.
3. Fullwvrve Rectifier Cfrcuit. This circuit provides fuiiwave
rectification of the 10 Hz signal. Filter Balance potentiometer R21 is used to equaiize peak heights of adjacent
haifwave pulses. Filter Rectifier potentiometer R30 is
used to adjust the rectification level of the rectifier to
the D.C. offset voltage level of the fiter ampiiñer.
19
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1
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5.2.3 638390 D.C. AhlPLlFlER BOARD AND
ASSOCIATED CI RCUlTRY
In the 638490 D.C. Amplifier Board, Figure 9-8, the fullwave rectified signal from the Filter/Rectifier Board is
conditioned by the following circuitry.
1. Response Time Selection Function of Switch SWI. The
first five contacts of Switch SW1 determine the electronic response time. The fastest available response,
0.5-second to 90% of the final reading, is obtained by
opening the contacts designated 1, 3, and 9 on the
board; and closing the two contacts designated 1T.
Longer response times are obtainable by appropriate
combination of switching settings.
a. Basic response time is selected by closing one or more
of the three contacts designated 1, 3, and 9. The
designations indicate time, in seconds, for 90% of
fiillscale response. Values thus selected are additive.
b. The two contacts designated 1 T provide an optionaí
multiplication factor of 2X. With these contacts in
clded position (marked lT), effective response time
is the sum of the values selected with the contacts
marked 1,3, and 9.
With contacts in open position (designated 2T in
Figure 9-8), but not marked on the board), effective
response is mice the sum of the values selected with
the contacts marked 1,3, and 9.
NOTE
guzriging the response time will necessitate readjustment of Bias Adjust Potentiometers R33 and R34,
item 4.
I
I
2. Low-Pass Filter. This active füter utilizes operational
amplifier ARl to smooth the fullwave-rectified signal.
3. D.C Amplifier and Associated Feedback Divider (Range
Resistor Network). The output signal from the low-pass
fdter circuit is applied t o an operational amplifier
circuit. It consists o f high-gain D.C. amplifier AR2,
connected in an operational amplifier configuration. The
feedback divider associated with AR2 provides the
capability of varying the D.C. gain, to permit use of
different operating ranges. The feedback signal is applied
to input 2 of AR2 via one deck o f the front-panel
RANGE Switch.
With RANGE Switch at position 1, overall gain of the
syktem is adjustable with the front-panel GAIN Control
(Paragraph 5.2.2.).
With RANGE Switch at position 2, the gain of AR2
may be adjusted with trimming potentiometer R9.
Range 2 gain is adjustable from 1X to 3.5X the Range 1
gain.
With RANGE Switch at position 3, the gain of AR2
may be adjusted with trimming potentiometer R15.
Range 3 gain is adjustable from 2X to IOX the Range 1
gain.
4. B h Adjustment Potentiometers R33 and R34. These
controls apply an adjustable zero-biasing signal to the
22
input of the D.C. Amplifier, to null out instrument
component electronic offsets. Electronic zero may be
established as follows:
a. With RANGE Switch set for highest-sensitivity range
that wili be used in operation, G A I N Control is set at
counterclockwise limit to remove all signal from
input of amplifier circuitry, and ZERO Control is set
at clockwise limit to remove all compensation for
normal optical offset signals.
b. Coarse Bias Adjustment R33 is adjusted so meter or
recorder reads 50% of fullscale or, if this is unobtainable, until maximum reading is obtained.
c. Fine Bias Adjustment R34 is adjusted back and forth
to find the extremes to which meter or recorder can
be varied with R34. "hen, R34 is adjusted so meter
reads approximately midway between these extremes.
d. Coarse Bias Adjustment R33 is adjusted so meter
reads approximately zero. ?hen, R34 is adjusted for
exact zero reading.
5. Front-Panel Zero Control. This control applies an additional zero-biasing signal to the input of the D.C.
Amplifier, to null out the normal optical offset signal.
With zero standard gas (normally, dry Nz) passed
through the analyzer, the input signal to the amplification circuitry, and therefore the meter reading should
ideally be zero. Ordinarily, however, a small input signal
is present. This is due to slight inequality between
intensities of the two sources, differences between
transmission characteristics o f the sample and reference
cells, out-of-phase signal, etc. This residual imbalance
signal is minimized with the SOURCE BALANCE
Adjustment, Source Alignment Adjustment (Vertical
Positioning Screw), and, if necessary, by an adjustable
optical shutter on the sample and/or reference celis, as
required. (Refer to Paragraph 5.2.8.)
After the best possible minimum has been achieved,
the SOURCE BALANCE Control is offset, by an
amount determined by the size of the residual imbalance, to bias the optical system into linearity. It is the
electronic signai induced by this normai optical offset
which is nulled out, i.e., compensated, with the ZERO
Control. With the zero standard gas stili flowing through
the analyzer, the final zero adjustment is made by stting
the front-panel ZERO Control for zero reading on meter
or recorder. After the ZERO Control has been set as
directed in Paragraph 3.1, the amount of compensating
signal fed into the zero-biasing input of the D.C.
Amplifier is automatically adjusted in proportion to
changes in setting of the GAIN Control, thus ensuring
proper compensation independent of G A I N setting:
On instruments operated at high-sensitivitysettings of
the RANGE Control, finer adjustment of the ZERO
Control may be desired, and is obtainable by dipping
the jumper that normaily bypasses R30. Removal of the
jumper will necessitate readjustment of Coarse Bias
potentiometer R33, and repetition of the Bias and
ZERO Adjustment steps.
6. Slide Switch SW2 and Voltage Output Jumper. These
two items control routing of the output signal from D.C.
amplifier AR2.
Slide Switch SW2 is set at the position marked “E,I”
to -obtain either the standard (non-linearized) voltage
output or the optional current output, and at “UN” to
obtain the linearized voltage output provided by the
optional 633756 Linearizer Circuit Board.
If a jumper is connected between the points marked
STRAP FOR E OUTPUT, the output signal is routed to
ground via a voltage divider associated with SW1 (item
6) to provide a selectable voltage output. The jumper is
not used if the signal is to be routed through the
optional 630153 Current Output Board or the optional
633756 Linearizer Board.
7. Potentiometric Output Selection Function of Switch
SWI. The desired potentiometric output is obtained by
closing the corresponding contact on Switch SW1, thus
selecting the appropriate tap on the voltage divider
mentioned in item 6. Contacts are marked: ‘D.OlV,”
“OO.1V,”“lV,” and “5V.”
8. Meter Sensitivity Adjustment Potentiometer R15.
Potentiometer R15 permits adjusting the fullscale sensitivity of the meter so that meter readout agrees with
recorder readout.
5.2.4 6301 53 CURRENT OUTPUT BOARD (Optional)
The 630153 Current Output Board, Figure 9-9, includes the
following circuits acd components:
1. An Emitter-Follower Stage. It uses transistors Q3 and
Q l to convert the signal from the 638490 D.C.
Amplifier Board paragraph 5.2.3) into an output
suitable for driving a current-actuated recorder or other
output device. Transistor 4 2 prevents Q1 from being
turned on by leakage currents.
2. Diode Rectifiers C R l and CR2, and Filter Capacitor C1.
These elements, together with the 90-volt center-tapped
secondary of transformer T I on the 633842 +15.5
Volt/-15 Volt Power Supply. Paragraph 5.2.7, constitute a floating power supply for the emitter-follower
stage.
3. Milliampere Output Switch. This slide switch provides a
choice of two outputs, to permit use o f a current
recorder with a fullscale span of either 4 to 20 m A or 10
to 50 mA. Circuit parameters are such that, with the
switch in position appropriate to íhe particular recorder,
a signaí-voltage level of -5 volts at pin C of the current
output board results in a fullscale recorder reading.
.
5.2.5 633756 VOLTAGE LINEARlZER BOARD
(OPTIONAL 6i6443 VOLTAGE LINEARIZER KIT)
The output signal from the 638490 D.C. Amplifier Board,
Paragraph 5.23, is proportional to absorption of optical
energy in the sample cell, and is therefore not linear with
respect to the concentration o f the measured component. If
desired, however, the 633756 Voltage Iinearizer Board,
Figure 9-10, may be used to equip a given operating range
for linear readout of concentration on the meter and on a
potentiometric recorder.
Straightening of the absorbance-versusconcentration
curve is accomplished by sequential adjustment of eight
odd-numbered trimming potentiometers designated R19
through R33. Each controls the gain of an associated
operational amplifier.
Setup and calibration of the board are explained in
Paragraph 7.2.
5.2.6 638436 mA LlNEARlZER BOARD
(OPTIONAL 616442 m A LINEARIZER KIT)
The 638436 m A Linearizer Board, Figure 9-1 1, equips the
analyzer for linear readout on the desired one of three
operating ranges: 1, 2, or 3. The board provides a switchselectable output of 4 to 20 m A or 10 to 50 mA.
Setup and calibration of the board are explained in
Paragraph 7.3.
5.2.7 633842 +15.5 VOLT/-lS VOLT POWER SUPPLY
The 633842 t 15.5 Volt/- 15 Volt Power Supply,
Figure 9-1 2, consists o f
1. Two identical, regulated adjustable power supplies. Each
supply utiiizes one 19.6-volt secondary of power transformer TI to drive a fullwave. rectifier circuit consisting
o f diode bridge and filter capacitor. A senes-type
integratedcircuit voltage regulator holds the output
constant. Output voltage is adjustable via a trimming
potentiometer: R4 for the -15 volt supply; R5 for the
t15.5 volt supply. Negative output of the t15.5 volt
supply and positive output o f the -15 volt supply are
connected to circuit ground at test point TE.
The +15.5 volt and -15 volt outputs are used for
individual amplifiers on the various circuit boards, and
for the zero-biasing circuit associated with the frontpanel ZERO Control (Paragraph 5.2.3).
2. A 90-volt center-tapped secondary of transformer T1.
This secondary drives a rectifier circuit on the optional
630153 Current Output Board. The transfomr winding
and the associated circuit constitute a floating power
supply for the emitter-foiiower stage. Refer to Paragraph
5.2.4.
5.2.8 637861 OR 637862 REGULATED A.C. SOURCE
POWER SUPPLY, FRONT-PANEL SOURCE
BALANCE ADJUSTMENT, OUT-OFPHASE
ADJUSTMENT, AND OPTICAL SHUTTERS
The Regulated A.C. Source Power Supply is provided
under two Part Numbers: 637861. for Explosion-Proof
Model 865; and, 637862, for Generai-Purpose Model
864/865. The power supply provides a regulated, adjustable
a.c. output to drive the dual infrared sources. Output
voltage is adjustable via dual potentiometer R7. See Figure
9-13. Recommended setting for most applications is 28.5 to
29.5 volts a.c. However. a setting of 3I .O to 32.0 volts a.c.
23
J
is recommended for high-sensirii*i@applications such as:
I . 0 to 50 or O to 100 ~1106CO in air;
2. O to 100 p/106 COZ,where the Model 865 constitutes a
component unit of a Model 9 15A Total Organic Carbon
Analyzer; and
3. differential analysis, A COZ 50 P/106, wing Model 865
equipped with flow-through reference cell.
Note that a.c. voltage regulation is accomplished by
clipping the waveform; thus the regulated output is nor a
true sine wave, and wiU iiof give a true a.c. reading on most
commonly used multimeter% e.g., Simpson, Triplett. At
normal operating levels of the output voltage, a multimeter
will read one to two volts higher than the true a.c. value.
Front-Panel SOURCE BALANCE Adjustment
As shown in Figure 9-1,the Rower supply output is applied
to the sources via a resistor bridge that includes the frontpanel SOURCE BALANCE Adjustment. This potentiometer adjusts the relative intensities o f sample and reference sources, to compensate for slight inequality in
characteristics of the two sources, differences between
transmission characteristics o f sample and reference
cells, etc.
ideal response of the meter or recorder to manipulation
of the SOURCE BALANCE Adjustment is exemplified by
the curve of Figure 54, A. Assume that initially, the
SOURCE BALANCE Adjustment is at its counterclockwise
limit. intensity of the sample beam is now considerably
greater than that of the reference beam, resulting in an
appreciable upscale reading on the meter or recorder.
Clockwise rotation of the SOURCE BALANCE Adjustment
will decrease tlie relative intensity of the sample beam, and
w
i
l
ltherefore decrease the meter or recorder reading. When
the SOURCE BALANCE Adjustment reaches its midrange
point, sample and reference beams w
i
l
lbe o f equal intensity; therefore, the meter or recorder will read zero (or
near-zero value). Further clockwise rotation o f the
SOURCE BALAKCE Adjustment beyond the midrange
setting will decrease the intensity o f the sample beam to a
value less than that of the reference beam. Consequently,
the reading wvüi rise above zero, or above the near-zero
minimum previously obtained, and will continue t o rise
until the SOURCE BALANCE Adjustment reaches its
clockwise limit.
Effect o f out-of Phase Signal Component
Ideally, the meter or recorder reading shouid be reducible
t o zero via the SOURCE BALANCE Adjustment, as
described above and as shown in Figure 54, A. In practice,
however, a zero reading may be unobtainable. If so, the
probable cause of the residual signal imbalance is excessive
out-of-phase signal component due to misalignment of the
optical system. The result is that the Characteristic curve for
the SOURCE BALANCE Adjustment has the shape shown
in Figure 54,B. This curve is similar t o the ideal curve of
Figure 54,A. except that, at the null setting of the
SOURCE BALANCE Adjustment, where beam intensities
are equal, the meter or recorder reading is an upscale value
instead o f zero. To correct this condition, the Vertical
Positioning Screw on the Motor/Source Assembly, Figure 3-2,is used to move the sources up or down, as required
to minimize the reading.
Sample Beam Totally Blocked
Referance Beam Totally Blocked
I
1-
SOURCE BALANCE
Adjustment Range
I
Sample Beam Totally Blocked
Reference Beam Totally Blocked
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A. IDEAL RELATIONSHIP: NO OUT-OF-PHASE
COMPONENT, CURVE SY MMETRICAL
,
Figure 5-4. Response of Meter or Recorder t o SOURCE BALANCE Adjustment
24
'-SOURCE
BALANCE
Adjustment Range
-'
B. NON-IDEALRELATIONSHIP APPRECIABLE
OUT-OF-PHASECOMPONENT
Normal Operating Setting of
SOURCE BALANCE Adjustment
Sarmal operating setting for the SOURCE BALANCE
Adjustment is clockwise from null point, causing intensity
of the sample beam to be slightly less than that of the
reference beam. Otherwise, if the SOURCE BALANCE
Adjustment were set exactly at the null point, subsequent
slight drift of the sources might cause the intensity of the
sample beam to become digllrly greater than that of the
reference beam. Sample monitoring under these conditions
would result in anomalous meter response at the lowconcentration end of the readout range; i.e., in this region
the meter would drive downscale when it should give a
small upscale reading.
In addition, adjustment of the SOURCE BALANCE
away from the null point is necessary in order to bias the
optical system into the linear regions of Figure 5-4, B.
Checking Status of SOURCE BALANCE Adjustment
Before íriitial zero and upscale calibration of the analyzer,
the SOURCE BALANCE Adjustment must be set as previously described. However, preparatory to subsequent
routine zero and upscale calibrations, it is desirable to
check the status of the SOURCE BALANCE Adjustment
without disturbing its setting unless necessary. This check is
made by noting response of the meter or recorder to insertion of the card into each beam in turn:
1. Set ZERO Control to clockwise limit.
2. Set RANGE Switch for the highest-sensitivity range that
will be used in operation, with GAIN Control at normal
operating setting.
3. Very slowiy insert card into the sample beam. As this is
done, the reading on the meter or recorder should move
continuously upscale, and should go offscale or reach a
maximum when beam is totally blocked. Next, very
sZowly insert the card into the reference beam. The
reading should first move downscale to a minimum,
which is at least three times smailer than the original
signal, sliould then move upscale, and should go offscale
or reach a maximum when beam is totally blocked.
If response is as described, the SOURCE BALANCE
Adjustment is correctly set.
If response is incorrect the SOURCE BALANCE
Adjustment must be reset by the specified procedure.
5.2.9 63 1688 DETECTOR TEMPERATURE CONTROL
BOARD AND ASSOCIATED ELEMENTS
The 631688 Detector Temperature Control Board,
Figure 9-14, utilizes temperature sensor RT1, a thermistor
mounted adjacent to the detector. See Figure 9-1. The
circuit board controls application of electrical power to
125-watt resistive heating element R10, thus maintainiig
temperature at the sensor poinr at approximately 140'F
(6OOC). When the circuit is in control, the light on the
board will blink at intervals of approximately one second.
5.2.10 635883 CASE TEMPERATURE CONTROL
BOARD AND ASSOCIATED ELEMENTS
(MODEL 865 ONLY)
The 635883 Case Temperature Control Board, Figure 9-1 5,
utilizes temperature sensor RT2. See Figure 9-1. The circuit
board controls application of electrical power to 1SO-watt
resistive heating element HRl 1, thus maintaining temperature at the sensor poitit at approximately 120°F (49OC).
Blower fan B2 provides air circulation throughout the
analyzer case.
The Model 864 uses fan B2 only, without the
temperature-control circuit.
5.2.11 633920 CALIBRATION POWER SUPPLY AND
ASSOCIATED ELEMENTS OF OPTIONAL
GASLESS CALIBRATION ACCESSORY
As shown in Figure 9-1, the optional gasless calibration
circuit consists of the 633920 Calibration Power Supply,
the front-panel CALIBRATE Pushbutton, and rotary
solenoid K1. Depression of the CALlBRATE Pushbutton
actuates the solenoid. causing it to insert a neutral density
filter into the sample beam. The fdter simulates a specific
concentration of the measured component. Note that the
simulated concentration value is valid only for operation at
a particular ambient pressure. A change of pressure of
1inch of mercury (3.38 kPa) will result in a readout error of
3% of fullscale. Therefore, if barometric pressure changes
significantly it is advisable to recheck calibration against an
upscale standard gas.
Within the 633920 Calibration Power Suppiy, Figure
9-15, transformer TI provides 24 volts a.c. to drive a fullwave rectifier consisting of diode bridge CRl and filter
elements R1 and C1.
5.2.12 646093 RANGE I.D. CABLE ASSEMBLY
(Optionai)
The 646093 Range I.D. Cable Assembly provides contact
closure signals that enable a computer or other external
device t o determine the range m a n d y selected with
front-panel RANGE Switch SW1. The cable is connected to
RANGE Switch SWl and extends to connector JIO,
mounted on the rear of the case.
5.2.13 646095 REMOTE RANGE KIT (Optiond)
The 646095 Remote Range Kit permits remote selection of
operating range by a computer or other device. This feature
is accomplished by the addition of the 646004 Range
Board, Figure 9-17. This relay board contains its own
power supply, and is connected to the RANGE Switch and
to connector J11 at the rear of the case.
25
ANEXO 3
.
8-4489
Model 660
Dew Point Hygrometer System
TM 77-260
EG&G
Environmental Equipment Division
151 Bear Hill Road
Waitham, Massachuam 02154
617/890-3710
NOTE: This instrument is designed to operate on either 115 or 230 VAC. Read the “Preparatiop for
Operation” section on page 61 of this manual before plugging instrument into a source of AC power.
AUGUST 1980
SPECIFlCATlONS FOR MODEL 660 DEW POINT HYGROMETER
Dew Point Range
Dew Point Accuracy.
-50°C to
+ 100°C
t0.3"C ( 054°F) nominal at 0°C
Depression
60°C (108°F) nominal at ambient temperature
of 25°C (77°F)
Depression Slew Rate
2°C (4°F) second maximum
Dew Point Sensit ¡vity
i: 0.06"C
Sample Flow Rate
0.25-2.5 literslminute (0.5-5.0 scfh)
Sample Pressure
0-21 Kglcm2 (0-300 psia)-Standard Housing
0-3 Kg/cm2 (0-40 psia)-Mirror Microscope Housing
Ambient Temperature Range
-40°C to + 100°C (-40°F to + 212°F)- Sensor
0°C to + 50°C (32°F to + 12O"F)-Control Unit
Auxiliary Coolant
Water (or other)-2 literslminute (0.5 gallonIminute) at
100 psig maximum, to augment cooling capability of
Sensor when necessary.
Dew Point Temperature Sensor
3-wire platinum resistance thermometer (PRT) 100 ohms,
nominal at 0°C.
Dew Point Outputs(s)
Standard:
(1) -5 to + 10 VDC over range -50°C to + 100'C.
(2) 100 ohms nominal (Cannot be used with above
analog output.)
Optional:
(1) 3 112 digit 8-4-2-1 parallel BCD digital data. T2L
compatible.
(2) 4-20 M A DC
-
(
0.1"F)
+ 100°C,
Display
3 112 digit digital data display, -5OoC to
resolution 0.1 "C
Alarm
DPDT contact closure rated at 3 amps at 28 VDC or 115
VAC with resistive load. Adjustable over entire range.
Remote Sensor
Up to 150 meters (500 feet).
Sensor Materials
Gold mirror, glass, epoxy, anodized aluminum.
Balance
Automatic self-standardization at 6,12, or 24 hours.
Factory set at 6 hours for 1.4-minute duration (both
adjustable).
Power Requirements
1151230VAC
Weight
6.8 K g (15 pounds)
lo%, 50-60 Hz, 60 watts max.
O
'A detailed error analysis discussing the nature and relative magnitude of errors is available on request.
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PART 111
- TECHNICAL INFORMATION
This part of the manual contains the principles of operation for each of the major circuit areas of the
Model 660 Dew Point Hygrometer. Figure H1 serves as a block diagram for all circuit discussions.
Section H
- THERMOELECTRIC DEW POINT
TEMPERA TURE CONTROL
CIRCUlTS
The thermoelectric dew point temperature
control circuit, described in Figure H1, serves
the purpose of heating and cooling the mirror
surface of the dew point Sensor to the temperature necessary to have a layer of dew on the
mirror that is in equilibrium with the moisture
in the sample gas in the Sensor, and to maintain
that equilibrium condition even though the
temperature necessary to do so may vary. To
accomplish this, an LED light source shining on
the mirror surface of the Sensor is driven from a
Constant Current Source. This circuit maintains
the LED current constant regardless of changes
in cable resistance, cable length, temperature,
etc. The light reflected from the mirror surface
in the Sensor is detected by a direct phototransistor. A separate LED and phototransistor
are also located in the Sensor and serve as bias
controls on the effects of temperature changes
on the LED output intensity and phototransistor
gain. The combined outputs of the direct and
bias phototransistors are used to drive the
Control Amplifier Circuit. if the mirror surface
is dry, this Control Amplifier Circuit instructs
the CoollHeat Power Amp to cool the mirror
surface. When too much dew forms on the
mirror surface, the Cool/heat Amp is instructed
to reduce the cooling level or even be instructed
to heat the mirror surface, if necessary. This
circuitry, ¡.e., the phototransistor sensing the
reflectivity of the Sensor mirror surface, the
Control Amplifier Circuit, and the Cool/Heat
Amp, are connected together to form a servo
controlled loop. When operating, i t adjusts itself automatically to control the Sensor mirror
surface at the temperature required to maintain
a layer of dew on the mirror surface in equllibrium with the gas sample around it.
When the Model 660 is in the self-standardization cycle mode, the servo loop described
above is interrupted, and the Cool/Heat Amp is
forced to heat the mirror surface to evaporate
any dew or frost present so that the circuitry
may automatically compensate for any changes
in mirror reflectivity, should they occur for any
reason. Once this compensation has been
achieved, the loop is reconnected together and
allowed to control on the dew point temperature
once more.
H1
1
I
I
Section J
- SENSOR PRT RESISTANCE TO
VOLTAGE CON VERTER
The temperature of the mirror surface is
measured by means of a Platinum Resistance
Thermometer (PRT) embedded beneath the
mirror surface. The resistance of the PRT device
varies almost linearly with change in tempera-
ture. The circuitry in this section interfaces with
the PRT with adjustmens for ZERO, SPAN, and
LINEARITY. The output is an analog voltage of
-5 VOC to + í O VDC that varies with temperature over the range of -5O'C to + 1OO'C.
Section K - AUTOMATIC SELF-STANDARDIZA TION (BALANCE) CIRCUITS'
The Model 660 automatically verifies its
own performance on a timed sequential basis by
means of an automatic self-standardization
circuit. This circuit adjusts for changes in the
condition of the mirror surface, or for changes
in any of the circuitry associated with the Sensor
optical system and control loop. Automatic selfstandardization is initiated upon instrument
turn-on. In addition, the self-standardization
cycle can be initiated automatically at 6,12-, or
24-hour intervals, user selectable. Model 660
Control Units are shipped prepared to initiate
an automatic self-standardization cycle every 6
hours.
complete the cycle. The bulk of the cycle time is
made up of a period of time when the dew point
sensor mirror surface isbeing heated above the
ambient temperature to remove any condensate
on it, either dew or frost. This heat time period
is adjustable to 1.4 minutes, 2.8 minutes, or 5.6
minutes. Model 660 Control Units are set to 1.4
minutes at the factory. When operating at-dew
point temperatures greater than lO'C, short
heat time periods still allow all condensate to be
evaporated from the mirror surface prior to
allowing the adjustment circuitry to compensate
for the mirror surface condition and any component changes. Longer heat times.are required
when operating at lower dew point temperatures. At the end of the selected time period,
the circuit will automatically balance the optical
bridge and control loop and return to normal
operat ion.
+
An automatic self-standardization cycle
may also be initiated manually at any time by
depressing the MANUAL BALANCE INITIATE
pushbutton on the Control Unit, or remotely by
momentacily shorting Pins X and 20 of the
Output Data connector. I t should be noted that
whenever an automatic self-standardization
cycle is initiated either manually by the
pushbutton provided, or remotely by means of
the Output Data connector, the internal timer
for the interval selected is reset and the selected
internal period, either 6, 12, or 24 hours, will
elapse before another self-standardization cycle
is automatically initiated.
Logic level signals are made available at
the Output Data connector for remote indication
of the operation of the Control Unit. The
BALANCE MODE digital output signal on Pin R
of J1 is normally high or + 15 volts DC when the
Model 660 is operating and is not In the aut*
matic self-standardization mode. When an
automatic self-standardization cycle is initiated
from any source, the signal out on Pin R of J1
will go low or very close to O volts DC.This Signal will remain low as long as thecontrol Unit ¡S
in the automatic self-standardization cycle.
Associated with the automatic selfstandardization cycle is the time required to
*Patented
K1
Section L
- ALARMSETAND PROTECTION
CIRCUITS
With the Model 660 electronics, it is possible to use the DPM to establish a set point for
operation of an alarm relay. Once the set point
has been established, between -5O'C and
+ 100°C, the alarm relay remains de-energized
as long as the actual dew point is below the
alarm set point, and energizes as soon as the
actual dew point increases to and above the
alarm set point.
the Sensor to shut down Sensor thermoelectric
current in the event that the Sensor base temperature exceeds +105'C. Since the Sensor is
designed to operate in ambient temperatures to
+lOO°C, it is possible, if attempting to read
very low dew points under these conditions, that
the energy dissipated in the thermoelectric
cooler can raise the temperature of the Sensor
base above + lOO'C, if it is not attached properly to a sufficient heat sink. i f this should occur,
the thermostat in the Sensor base will open
rather than risk damaging the Sensor.
The outputs of the alarm relay, a set of
double pole, double throw (DPDT) contacts, are
all brought to the output data connector for use
in customer provided alarm indicator circuits.
The analog temperature input signals to the
alarm set point circuitry are obtain'ed from the
output of the Track and Hold circuitry to prevent
false alarms from possibly occurring during
automatic self-standardization cycles as the
mirror temperature is increased above the
actual dew point.
The second of these protectiondrcuits also
relates to the high temperature operation for
which the Model 660 has been designed. This
protection circuitry monitors the Sensor Mirror
tem perature cont inuousiy and automat ¡cally
shuts off any current flow to the Sensor thermoelectrics should the mirror temperature exceed
1 W'C. The possibility of this occurring is primarily when the Sensor is at a high ambient
temperature, +5O'C to +lOO'C, and an automatic self-standardization cycle is initiated
which heats the mirror surface. This heating
could cause the mirror temperature to exceed
+lOO°C and damage the Sensor, but this clrcuitry protects against this possibility.
+
Inclbded in this section is a description of
the protection circuits that have been incorporated into the Model 660 electronics to prevent
damage to the Sensor from over-heating caused
by normal circuit operations. The first of these
circuits is a thermostat installed in the base of
L1
Section M
- DISPLAY CIRCUITRY
ing the Model 660 dew point temperature in
engineering units.
The Model 660 is equipped with a Fairchild
Model 70 Digital Panel Meter (DPM). This
meter has been modified to move the decimal
point from its normal position to one located one
place to the right. This modification allows the
DPM to display a -5 VDC to 10 VDC input as a
-5O.O"C to + 100.O'C output, thereby
. .. . present:
All technical data concerning the Fairchild
DPM are contained in the DPM Manual, which
is shipped as part of the Model 660 data
package.
+
M1
--
Section N
- TRACK AND HOLD CIRCUITRY
The purpose of the Track and Hold Circuitry is (1) to provide an analog dew point
temperature output that is identical to the direct
dew point temperature output as long as the
system is controlling on the actual dew point
temperature, and (2)to provide a steady output
corresponding to the actual dew point value just
prior to an automatic self-standardization
(balance) cycle, during the entire cycle. The
time when the two outputs are identical is called
the Track mode, and the time spent during the
self-standardization cycle is called the Hold
mode. By attaching process control instrumentation to the output of the Track and Hold circuitry, rather than to the direct output of the
Sensor mirror PRT readout circuitry, the mirror
temperature increase and decrease that occur
during the self-standardization cycle can be
effectively “masked” during this period.
A single-pole, Form B relay is used to disconnect the input to the Track and Hold circuitry
during the self-standardization cycle. Previous
information of analog dew point temperature is
“remembered” during thls time by a large, low
leakage capacitor. This capacitor Is buffered by
an amplifier to isolate the capacitor from the
output.
During the self-standardization cycle initiated automatically at power turn on, the output
of the Track and Hold circuitry should be
ignored since there was no previous dew point
data to be retained.
N1
Section P - D E W POINT DATA SHEETS AND INFORMATION
EG&G Dew Point Hygrometer Sampling Systems
Basic Hurn ¡dity Definitions
Model 660 Simplified Schematic
P1
---__..------
--
~
EG&G DEW POINT HYGROMETER
SAMPLING SYSTEMS
~NERAL
Of all the factors considered in huidity measurement. One Of the ImSt
aportant. and that which most Often is
ven the least attention, is the sampling
,Stem. Considerations of leakage, presire and temperature gradients. and
j oisture
absorpti on/desorption characzristics are often overlooked.
The problem of leakage is relative;
e., if the dew point being measured is
lose to the ambient room dew point,
zakage into the system may not bias the
eading substantially. If the system is
ressurized above atmospheric so as to
reate a leakage out of, rather than into,
he system, the error introduced will be
ess. The degree to which leakage can be
olerated also depends heavily on the
ictual dew point being measured. As an
!xample, when measuring a dew point of
100°F with a sample flow rate of 4
ICFH. at an ambient or surrounding dew
>oint of SOOF, a leakage in flow of 5 x
10-5 SCFH will cause an error of l 0 F .
However, at a measured dew point of
+lOO°F the same leakage rate would
The
:Buse an error of only O.OOOOl°F.
area of leakage becomes significantly
more important and the error becomes
much larger in systems-operating below
ambient pressure.
Pro-Heating
If the dew point of the gas under
measurement is above the ambient temperature of the installation and the
sampling lines, both the lines and the
sensor must be heated with some type of
heater tape, or the line must be steamtraced in the usual fashion. The approach used will vary widely with the
specific nature of the installation. and
the user must use his own ingenuity to
assure that none of the sampling components be at a temperature lower than the
highest dew point anticipated. If electrical heater lines are used, it is
desirable to connect these to a variable
transformer to adjust the heatinir the sample lines are long, it may be
necessary to wrap them in insulating
cloth to minimize the amount of heat
required to do the preheating. The line
should be heated well above the dew
point and should not exceed the temperature rating of the sensor. A maximum of
2000F is usually recommended. Heating
above the dew point does not change the
dew point of the sample.
Selection of Sampling Components
MATERIAL MOISTURE PROPERTIES
Of equal importance is the effect
that
material
absorption/desorption
characteristics have on overall system
response.
Although not true of all
applications, stainless steel, glass and
nickel alloy tubing are the best possible
nonhygroscopic materials and should be
used for low dew point applications (OOF
to -100OF). Teflon is also satisfactory,
but begins reducing system response due
to desorption at the lower dew points.
Copper and aluminum alloys, as well as
stabilized polypropylene tubing, are acceptable above -200F dew point. Most
plastic and rubber tubing is unacceptable
in all ranges. Unless attacked by the
sample, the effect of the more hygroscopic materials is not of a contaminating nature, but actually one of
introducing severe lag into the system
during the establishment of an equiiibrium condition. For example. plastics
such as nylon cannot be used at low dew
points simply because the equilibrium
condition may actually take days to
stabilize. The actual selection of the
sample line material should be based on
the degree of permanency of the installation, with a minimum of joints, fittings, and other plumbing prior to the
hygrometer. Generally, stainless steel is
preferred for permanent installations
operating at low dew points. On stainless steel lines. either swage or flaretype fittings can be used.
All materials will absorb moisture to
some extent. The curves relate typical
desorption properties of common sampling line materials after being exposed
to a "wet" gas such as the ambient
atmosphere. The curves illustrate the
difficulty of obtaining a fast system
response when switching fkom a high dew
point sample to a low dew point sample.
Even if the instrument responds instantly, the sampling lines dictate the overall
response.
There are three types of pumps generally suitable for hygrometric work.
For installations where the sample is not
to be returned to the process. the Cast
Manufacturing Co. vane pump is acceptable. This pump offers a reasonably high
degree of reliability, and can handle
large volumes of air. The vane type of
pump does tend to contaminate the
sample with minute amounts of p u m p
wear products (iron. carbon). therefore,
it should be downstream of the hygrometer.
The dew point temperature of a gas is
a measure of the absolute moisture
content of the gas. regardless of the
temperature and pressure of the gas.
Most conversion tables for dew point (or
frost point), to parts-per-million, grainsper-pound. etc., are made at atmospheric
pressure (14.7 psia); therefore, if a c c v
rate absolute moisture content measurements are to be converted to a t m e
spheric-pressurereferenced values, the
pressure must be known. A pressure tap
after the hygrometer sensor can be
fitted with an appropriate pressure
gauge. Basic Humidity Definitions are
explained in Bulletin 3-050.
For general purpose use or for closed
loop sampling at atmospheric pressure,
any one of several types of diaphragm
pumps, such as the Neptune Dynapump,
can be used. The Dynepump utilizes a
neoprene diaphragm, and the pump housing is aluminum.
For most closed loop sampling where
leak tightness is essential. the welded
bellows types such as the Metal Bellows
MB-21 can be used.
PRESSURE MEASUREMENTS
CLEANING SAMPLING SYSTEMS
Most types of metal tubing contain
oil deposits on the interior walls due to
the manufacturing process. This residue
must be removed before putting the lines
into service in a gas sampling system.
Trichloroethylene or a similar solvent
can be used to clean individual lines and
.
__
-
components before assembly, with a f h l
flushing after assembly. The lines should
be purged dry with air or nitrogen before
being placed i n t o Service. I n addition to
the i n i t i a l installation, the process itself
may constitute a source of contamination and i n many applications these are
volatile hydrocarbons. An excellent f l u i d
for purging and cleaning the instrument
and/or the sample i s Freon 114. This i s a
&
&
;e
solvent since it is capable of
holding many hydrocarbons i n solution, it
is highly volatile, non-toxic, non-explosive, readily available, and w i l l not attack common sampling l i n e materials.
EG&G Dew Point Hygrometers are provided with Type A or Type B Cleaning
Solution for use in cleaning and conditioning the sensor mirror. Type A i s a
general purpose cleaner f o r most applications.
Type B is a special purpose
cleaner recommended f o r Heat Treating,
or similar applications. where o i l vapors
are present. This cleaner tends t o make
the sensor less sensitive t o o i l vapor
condensation.
CONTAMINATION EFFECTS
System contamination and i t s effect
on dew point measurement can be subdivided i n t o two categories
condensibles and noncondensibles. Before p r e
ceeding. it i s important that one understands that the optical dew point
analyzer measures the dew point. hence,
the vapor pressure, of any substance that
condenses on the mirror surface. Conversely, regardless of concentration,
contamination constituents in a sample
w i l l not condense on the mirror wless i t s
dew point temperature i s reached.
-
Condensibler
level of iO%476 mm Hg), i t s dew point
would be -35OC. Since this i s below the
water vapor dew point, it w i l l not condense on the sensor mirror.
However,
this means that there would be interference i f the water vapor dew point was
below -35OC. I f the contaminant is, i n
addition. soluble i n the constituent being
measured, i t w i l l modify the vapor pressure and, hence, the dew point of the
sample. The overall effect w i l l depend
on the degree of solubility.
Noncondensibier
The second category of contaminants
i s the noncondensibles, which can again
be subdivided into solubles, primarily
salts, and insolubles, consisting of particulate matter. The soluble contaminant
similarly w i l l modify the partial pressure, or dew point, being measured. This
type of contaminant affects a l l types o f
humidity instruments and necessitates
frequent cleaning of the dew point mirror, since heating the mirror w i l l not
remove the salts.
lnsoluble matter i s
most easily avoided through sample l i n e
filtration.
SAM PLiNG CONFIGURATIONS
A suggested sampling system for use
with EG&G Dew Point Hygrometers
would be one where a portion of the gas
line to be sampled is brought t o the
hygrometer location from a pressure tap
either b y using a suitably designed
vacuum pump, or by expanding the
sample t o a lower pressure. The flow
rate through this main sampling l i n e
-
___))
Condensibles can be further subdivided i n t o soluble and insoluble condensibles. If insoluble, and i t s dew point
i s at or above that of the constituent
being measured, the relative concentration level w i l l mainly determine the
effect on the measured dew point. If the
concentration level of the contaminant i s
low, ¡.e.,
i t has a low partial pressure
compared t o the water vapor, then the
e f f e c t of i t s presence can be standardized periodically before it degrades the
primary measurement. This is done by
heating the mirror surface t o remove the
condensate and rebalancing the optical
detection system. A t high concentration
levels the dew point analyzer may measure the dew point of the contaminant
rather than the water vapor dew point.
This problem i s lessened due to the high
attenuation characteristics of dew or
frost compared t o many of the common
contaminants. For example: i f a water
vapor dew point of O°C was being measured at atmospheric pressure (760 mm
Hg) and the ethylene oxide were present
as a contaminant at a concentration
-
NOTE: Considerable cost savings can
sometimes be made by recognizing that
the sample exhaust lines and related
components need not be as high a quality
and as non-hygroscopic as those prior t o
the hygrometer.
PROCESSBEING SAMPLED
FLOW CONTROL
HEATED SAMPLE
(0.5-5 SCFH)
PRESSURE
REGULATOR
(IF REQ'DI
11
II
FLOW CONTROL
lo1
'
BYPASS FLOW (IF REQ'D)
INCREASED TOTAL SAMWE
FLOW FOR FASTER RESPONSE
C3
VACUUM PUMP
(IFREQ'D)
EXHAUZI
P3
I
1
should be sufficient t o ensure continuous
flushing of the lines, i n order to provide
R fast response time for the sampling
system. Usually. the flow r a t e of 2-4
SCFH i n a 1/4" line is adequate; however, this number must be adjusted with
the length of the line. the level of
absolute moisture content of the sample,
and the desired response t i m e of the
sampling system. A bypass l i n e may be
used t o increase the main sampling line
velocity and improve the overall response time.
It is necessary that the
sampling l i n e be equipped with a valve
f o r adjusting the sample flow rate. The
sample for the hygrometer is obtained
from the pressure drop across the bypass
as shown. It is desirable t o provide the
hygrometer input w i t h a f i l t e r , especially
i f the gas under study contains particulat e contam inants.
Several sintered
stainless steel f i l t e r s are available which
are suitable.
It must be remembered
that the f i l t e r element i s considered a
hygroscopic item, which w i l l contribute
A
some l a g t o the sampling system.
rule-of-thumb i n the design of hygrometer sampling systems i s t o minimize the
number of components, such as valves,
tees, and f i l t e r s prior t o the hygrometer
input. The hygrometer output is connected t o a flowmeter and valve for
adjustirg the flow r a t e t o the recommended range of 2-4 SCFH.
_
.
I
I
I]
c
BASIC HUMIDITY DEFINITIONS
RELATIVE HUMIDITY
DALTON'S LAW
Relative Humidity i s the ratio of the acJohn Dalton was the first to surmise
that the total pressure, Pm, exerted by a tual vapor pressure (as defined by the
Tables) in the mixture to the saturation
mixture of gases or vapors is the sum of
the pressures of each gas if it were to oc- vapor pressure, with respect to water, a t
cupy the same volume by itself. The
the prevailing dry bulb temperature.
pressure which each gas component of a
multiple constituent gas (such as air) ex- Example 1. (Metric Units)
erts is called i t s partial pressure. if px,
I f dew point = lO'C and dry bulb = 25'C:
p , and pz represent the respective parY.
RH- = Vapor Pressure at ~O'C
tial pressures of gases X, Y , and Z in a
mixture, Dalton's Law states:
Vapor Pressure a t 25%
=4(
+R/ + & + .
..
.
Elementary as i t may seem, the concept
of Dalton's Law is often overlooked in
considering problems in humidity, because one forgets that the "water" in a
gas i s actually a gas itself and must be
treated in accordance with the gas laws.
Air must be considered a mixture of
gases oxygen, nitrogen, and water vapor
(neglecting the minor Constituents). All
discussions of humidity can then be reduced to discussions of water vapor
pressure, and all definitions encountered
in humidity can be expressed in terms of
vapor pressure.
-
= 12.272 mb
31.671 mb
~
Dew Point is that unique temperature to
which the air (or any gas) must be
cooled in order that i t shall be saturated
with respect to water.
FROST POINT
Frost Point i s that unique temperature
to which the air (or any gas) must be
cooled in order that it shall be saturated
with respect to ice.
The dew point or frost point DEFINES
the partial pressure of the water vapor
in the gas, from the Smithsonian Meteorological Tables.
Parts per million (PPM) by volume i s the
ratio of the partial pressure of the water
vapor to the partial pressure of the dry
gas.
Example 1. (Metric Units)
I f frost point = - 60'C and system total
pressure is 1013 mb (14.7 PSIA)
Parts
PPMV
= M
X
38.7%
s
I f frost point = - 4 5 ' ~
and dry bulb = - 40°C:
-
RH = Vapor Pressure at - 45'C (Actual)
Vapor Pressure at - 40°C
(with respect to water)
-
Vapor Pressure at SO'C
Total Pressure Water.Vapor
Pressure at SO'C
-
10.80 x -1 O- 3mb
x
(1013- 1 0 . 8 0 ~lO-3)mb
los
= 10.7PPM(by volume)
Example 2. (English Units)
I f frost point = - 70°F and system total
pressure is 14.7 PSIA (29.92'"g):
Example 2. (English Units)
Ifdew point = 50'F and dry bulb = 9O'F:
RH = Vapor Pressure at 50'F
Vapor Pressure at 9OOF
DEW POINT
PPM B Y VOLUME
PPM,
=
Million
-- -
= Vapor Pressure at 70'F
l+
Total Pressure Water
Vapor Pressure at 7OUF
= 4.974X10-4..Hg
(29.92
I f frost point = -50°F
and dry bulb = - 4O'F:
= 17PPM (by volume)
RH = Vapor Pressure at - 50'F (Actual)
Vapor Pressure at - 40°F
(with respect to water)
= 1 99OX 1O- 3"H
5.584X 1O-
= 35.7%
NOTE: RH is arbitrarily defined with respect to water even though it seems that
it should be with respect to ice at - 40'C
(- 40'F).
- .004974)"Hg
I
I
I
1
I
I
I
1
1
1
1
I
I
I1
1
i
I
P4
_-
-
I
--
-r---- ---
PPM BY WEIGHT
DEW POINTFROST POINT RELATIONSHIPS
p p by
~ weight of dry gas is identical to
p p by
~ volume except that the weight
ratio changes with the molecular weight
of the carrier gas.
Below 0.C (32"F),dew point hygrometers measure the frost point temperature
rather than the dew point. The tables below permit conversion from dew to frost
point. For a more accurate conversion, consult Table 102 of Smithsonian Meteorological Tables,
Example t . (Metric Units)
f frost point =
Metric Units YC)
- SO'C, system total
ressure is 1013 mb, and the carrier gas
IS
F.P.
hydrogen:
O
- 1
- 2
- 3
- 4
5
-6
- 7
- 8
-9
-10
-11
PPM, =PPM, X Mol. wt. of H20
Mol. wt of carrier gas
= 10.7 X 18 = 96.3PPM
-
-
(byweight)
Example 2. (English Units)
-
If frost point = 70'F, system total
pressure is 14.7 PSIA, and the carrier gas
is hydrogen:
(by weight)
F.P.
MOLECULAR WEIGHT
OF COMMON GASES
26
29
17
40
co
44
28
Ethylene
28
Helium
Hydrogen
Methane
Nitrogen
Oxygen
Sulfur Dioxide
Water
o
-1.2
-2.3
-3.4
-4.5
5.6
- 6.8
-7.9
-9.0
-10.1
-11.2
-12.3
-
I
PPM, =PPM, X Mol. wt. of H20
Acetylene
Air
Ammonia
Argon
co2
D.P.
-
4
2
16
28
32
64
18
1
+ 32
+ 31
+ 30
+29
+ 28
+ 27
+ 26
+ 25
+ 24
+ 23
+ 22
+ 21
+ 20
+ 19
+ 18
+ 17
+ 16
+ 15
+ 14
+ 13
+12
+11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
D.P.
+ 32
+ 30.8
+ 29.7
+ 28.6
+ 27.5
+ 26.4
+ 25.2
+24.1
+ 22.9
+21.8
+20.7
+ 19.6
+ 18.5
+ 17.4
+ 16.2
+ 15.1
+ 14.0
+ 12.9
+ 11.8
+ 10.7
+ 9.6
+ 8.5
- 13.4
- 14.5
- 15.6
- 16.7
- 17.8
- 18.9
- 20.0
-21.1
22.2
- 23.3
- 24.4
25.5
-
-
F.P.
t 10
+
+
+
+
+
+
+
+
+
9
8
7
6
5
4
3
2
1
O
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
-10
-1 1
F.P.
D.P.
F.P.
-24
-25
-26
-27
-28
-29
-30
- 31
-32
-33
-34
- 35
+
+
+
+
+
7.4
6.3
5.2
4.1
2.9
1.8
0.7
- 0.4
-
1.5
2.6
3.7
- 4.8
- 5.8
- 6.9
- 8.0
- 9.1
-10.2
-11.3
-12.4
- 13.5
14.6
- 15.6
-
-
D.P.
- 12 - 16.7
- 13 - 17.8
- 14 - 18.9
- 15
- 16
- 17
- 18
- 19
- 20
-21
22
- 23
- 24
- 25
- 26
- 27
- 28
29
30
-31
- 32
33
-
-
I
~
-26.6
-27.7
-28.8
-29.9
-30.9
-32.0
-33.0
-34.1
-35.2
-36.2
-37.3
-38.4
F.P.
D.P.
+
+
D.P.
- 20.0
-21.1
- 22.2
- 23.3,
- 24.3
- 25.4
-26.4
27.5
-28.6
29.6
30.6
-31.7
-32.8
-33.9
-35.0
-36.1
-37.2
-38.2
-39.3
-
F.P.
-36
-37
-38
-39
-40
-41
-42
-43
-44
-45
-46
O.P.
- 39.4
- 40.5
- 41.6
- 42.6
- 43.7
- 44.7
- 45.8
- 46.8
- 47.9
- 49.0
- 50.0
D.P.
F.P.
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
-51
- 52
- 53
-40.3
-41.4
-42.4
-43.5
44.5
-45.6
- 46.6
-47.7
48.7
- 49.8
-50.8
-51.9
52.9
-54.0
-55.0
-56.1
-57.1
-58.2
- 59.2
-60.3
-
-
-
REFERENCE: Smithsonian Meteorological Tables, Sixth Revised Edition, List, Roben J.,
Publication No. 4014, Smithsonian Institution. Washington, 0.C
PRESSURE CONVERSION
AS
the torid pressure of a gas sample changes, all of the partial pressures comprising the total pressure change in the same ratio.
Example 1. (Metric Units)
If frost point = - 60% and system total PreWre is 1013 mb ( 1 .O33 kg/cm2), what is the dew point at 21 kg/cm2?
Vapor Pressure at - 60% = Vapor Pressure a t New Dew Point
1.O33 kg/cm2
21 kg/cm2
Vapor Pressure at New Dew Point = 10.80 X 10-3mb X
1 .o33
= .2195 mb partial pressure
From the Vapor Pressure Tables (over ice), the Frost Point = - 35.2'C
Example 2. (English Units)
I f frost point = -7O'F
and system total pressure is 14.7 PSIA, what isthe dew point a t 70 B I G (84.7 PSIA)?
Vapor Pressure at - 70'F
14.7 PSIA
= Vapor Pressure at New Dew Point
84.7 PSIA
Vapor Pressure at New Dew Point = 4.974 X
Hg X
From the Vapor Pressure Tables (Over ice), the Frost Point
DEW POINT/PRESSURE CONVERSION CHART
100
90
80
70
-80
50
U)
30
k
Lym
a
s 10
I-
[ O
Ly
-10
-m
-30
-40
-50
-60
-70
-80
-90
-100
84.7 = 2.87
14.7
= - 44.5'F
X
Hg partial p r m n
PSYCH ROMET R IC CHART
(BAROMETRIC PRESSURE 29.92" Hg)
0
a
>
a
o
8
o
z
oa
3
W
o
W
a
2
U
O
10
D R Y BULB TEMPERATURE
I
- DEGREES F
P7
v)
t
8
MANUAL DE OPERACIONES
E INSTRUCCIONES DE MANTENIMIENTO
~
-
Para Bombas de Vacio
FE4600
--
FE-I700
FABRICANTES DE EQUIPO PARA LABORATORIO E INDUSTRIA, S. A.
PROL. PASEO LOMAS ALTAS No. 330 FRACC. LOMAS DEL VALLE
c
TELS. 414148 41-18-87
GUADALAJARA, JA L. MEX IC0
_r
-
PRECAUCION: Nunca lubrique este tipo de bombas, pues sus alabes de carbón y los rodamientos sellados del m o t o r no requieren aceite o grasa.
CONSTRUCCION: L a mayor parte de los componentes de estas bombas son de fierro vaciado. Por lo
tanto cualquier 'humedad que se acumule e n la bomba tenderá a oxidar y corroer el interior cuando esté parada. Los alabes están fabricados de carbón duro y rectificados, su duración aproximada es de
4,000 a 7,500 horas dependiendo de las condiciones de vacío o presión a que la bomba se trabaje.
ARRANQUE: L a bomba debe instalarse preferentemente en un lugar limpio y ventilado y localizadas
lo más p r ó x i m o al sistema para ser aprovechadas efícienternente. Antes de conectar la bomba asegúrese que su fuente de energía coincida c o n el mismo voltaje. fases y frecuencia del motor. Todos los motores tienen garantía y servicio otorgado por el fabricante, usualmente tienen protector térmico contra
sobrecargas. Antes de conectar su bomba c o n un sistema es recomendable familiarizarse con el funcionamiento de la misma. L a mejor eficiencia se obtiene después de un lapso de tiempo cuando la bomba
ha alcanzado su temperatura de operación.
MANTENIMIENTO: Los cuatro alabes pueden ser cambiados fácilmente quitando la tapa frontal. es
necesario sopletear con aire a presión y limpiar la cámara antes de instalar los alabes nuevos.
No quite nunca el rotor ni afloje o quite los tornillos que sujetan el anillo con el cuerpo pues se modificarían las tolerancias reduciendo la eficiencia de la bomba.
LIMPIEZA: Si se permite que la bomba trabaje c o n los filtros sucios o sin los filtros, suciedad excesiva.
partículas extrañas, humedad y muchas otras cosas pueden acumularse en la cámara. Cualquiera de esto ocasiona que los alabes trabajen forzados pudiendo atazcarce o romperce. Para solucionar esto lave
la bomba, retire los filtros y c o n la bomba funcionando ponga pequeñas cantidades de solvente* en la
succión en repetidas ocasiones cuando todo el solvente haya salido de la bomba ponga los filtros nue
vamente. Para limpiar los filtros cepille el exceso de'mugre
.. *
y lave c o n solvente. Seque bien antes de instalar.
*Recomendamos tener mucha precaución al 'usar solvente, use alcohol, carbón Zetracloruro. No use
keroseno.
GARANTIA: Todos los productos FELI, están garantizados contra cualquier defecto de fabricación
(excepto piezas de desgaste normal) por un periodo de un año. L a garantía no será efectiva si la bomba ha sido desarmada o reparada y en especial si algún elemento extraño o liquido entró a l a csmara de
la bomba.
PELIGRO: No se use el equipo para bombear combustibles líquidos o vapores porque puede ocurrir
una explosión.
ANEXO 5
VISI-FLOAT"FLOWMETER
Installation and Operating Instructions
'L
DIMENSIONS
7
- IN INCHES
-
B
I
E
-----I
I
n
Figure1
.--
Dwyer Visi-Float@ Series Flouemeters are furnished in two
models (see Figure 1 ) each available in a broad choice of flow
ranges with direct reading scales for air, gas or water. Installation, operation and maintenance are very simple and only a
k...
,=" cüixmcn sense precautions must be observed to assure long,
trouble-free service.
CAliBRATlON
Each Dwyer flowmeter is calibrated at the factory. If at any
time during the meter's life, you wish to recheck its calibration,
do so only with devices of certified accuracy. DO N O T attempt
to check the Dwyer Visi-Float@ Flowmeter with a similar flowmeter as seemingly unimportant variations in piping and back
pressure may cauae noticeable differences in the indicated reading. If in doubt, retÚrn your Dwyer flowmeter to the factory.
It will be calibration checked for you at no charge. Before
proceeding with the installation of your Dwyer Visi-Float@
Flowmeter. check to be sure you have the model and flow
range you require.
LOCATION
TEMPERATURE, PRESSURE, ATMOSPHERE, A N D VIB R A T I O N : Visi-Float@ Acrylic Flowmeters are exceptionally
tough and strong. They are designed for use at pressures up
to 100 PSI and temperatures up to 150deg. F. DO N O T EXCEED THESE LIMITS! The installation should not be erposed to strong chlorine atmospheres or solvents such as
8
.
R
n
A
INSTRUMENT
.
\.--
_sax 373 _MICHIGAN
-_
CITY. INDIANA
benzene, acetone, carbon tetrachloride, etc. The mounting panel
should be free of excessive vibration since it may prevent the
unit from operating properly.
I N L E T PIPING RUN: It is good practice to approach the
nowmeter inlet with as few elbows and restrictions as possible.
In every case the inlet piping should be at least as large as
the connection to the flowmeter Le. I/8" Iron Pipe Size. Length
of inlet piping makes little difference for normal pressure fed
flowmeters.
For flowmeters on vacuum air service the inlet piping should
be as short and open as possible. This will allow operation
near atmospheric pressure and thereby insure the accuracy of
the device. (Note that for vacuum air service the flow control
valve if any, should be on the discharge side of the flowmeter.
Either the T M V unit or a separate in line valve may be applied. )
DISCHARGE PIPING: As on the inlet, discharge piping should
be at least as large as the nowmeter connection. In addition,
for pressure fed flowmeters on air or gas service the discharge
piping should be as short and open as posiibie. This will allow
operation of the now tube at near atmospheric pressure and
insure the accuracy of the device. This is of less importance
on water or liquid flowmeters since the flowing medium is generally incompressible and moderate back pressure will not
affect the accuracy of the instrument as calibrated.
BULLETIN F.33
PAGE 2
FLOWMETER
Instructions
VISI-FLOAT
@
~-
Series VF VISI-FLOAT' Models and Ranges
- 2" Seale
Model VFA
Range
SCFH Air
.l-1.0
Range
LPM Air
ing NO.
1
.06-.5
ing N O .
21
22
2
1
.6-5.0
3
1
1.0-10
4
1
.CS
23
2.0-20
5
1
1.0-10
24
4.0-30
.-.
6
1
5.0.50
7
1
3.025
25
.15-1.0
I
Cal. Water
per hour
- --
6-Yl
I
32
._
33
I
I
I
.6-5
- 4" SC8le Order-
SCFH Air
1
I
I
I
1
I
per min.
10-100
Range
I
I
I
CC water
I
Model VFB
Order-
.22.0
~~
8
Order-
ing NO.
50
Sl
3-3.0
1.10
2-20
51
4-40
Y
10-100
15-154
53
20.200
55
54
CC Air
per min.
2-10
41
a2
840
44
.
I
loQlO00
I
I
I
60
LPM Air
1-10
I
-
-
6 6 1
1
CC Water
per min.
Gal. Water
per hour
.5-12
POSITION AND MOUNTING
CAUTION
111 Visi-Float* Flowmeters must be mounted in a vertical position
vith the inlet connection at the bottom and outlet at the top.
Do not completely unscrew valve stem unbsr flowmeter Is
unpressurized and drained of any liquid. Removal while in
service will allow gas or liquidto flow out front of valve body
and could result in serious personal injury.
-
;URFACE MOUNTING: Drill appropriate holes in panel using
.he dimensions shown in Figure 1. Hold the flowmeter in position
n front of the panel and instafl the mounting screws through the
,anel from the rear. Pipe iip inlet.and dischargeusing R T V silicone
;ealant or Teflon@ tape on pipe threads to insure against leakage.
SURFACE M O U N T I N G O N P I P I N G ONLY: An alternate
method of surface mounting omitting the mounting screws and
supporting the Visi-Floate Flowmeter on the connecting piping
mly is possible. For this method extra long or straight pipe
threads should be used so that nuts may be run onto the pipe and
later tightened against the back of the panel to retain the unit in
proper position. Use the appropriate hole layout information from
Figure 1, but omit the small holes.
M O U N T I N G O N P I P I N G ONLY W I T H O U T P A N E L : For a
temporary or laboratory type installation, the panel may be
omitted altogether and the flowmeter installed directly in rigid
piping. Its light weight permits this without difficulty.
OPERATION
To start system, open the valve slowly to avoid possible damage.
Rate of flow is read at the point of maximum width of indicator
float. Control valves on B V and SSV models are turned clockwise
to reduce flow, counter clockwiseto increase flow. A nylon insert i s
provided in the threaded section of the valve stem to give a firm
touch to the valve and to prevent change of setting due to
vibration.
Litho in U.S.A. 10f03
52t4024100
0 Copyright 1983 Dwyer Instruments Inc.
. -
MAINTENANCE
The only maintenance normally required is occasional cleaning to
assure reliable operation and good float visibility.
DISASSEMBLY: The flowmeter can be disassembled for cleaning by simply disconnecting the piping, dismounting the unit
from the panel and removing the top-plug-bd stop. Take out the
ball or float by inverting the body and d o w i n g the float to f d
into your hand. (Note: It is best to cover the discharge port to
avoid losing the float through that opening.)
C L E A N I N G : The flow tube and flowmeter body can beat be
cleaned with a little pure soap and water. Use of a bottle brush or
other soft brush will aid the deaning. Avoid benzene, acetone.
carbon tetrachloride, alkaiine detergents, caustic soda, liquid
soaps (which may contain chlorinated solvents). etc. and avoid
_ prolonged immersion.
..
REASSEMBLY: Reistall the float. remount, connect and place
the unit back in service. A little stop cock grease or petroleum jeiiy
on the "O" rings will help maintain a good seal as well as facilitate
--.
assembly. No other special care is required.
ADDITIONAL INFORMATION
For additional flowmeter application information, conversion
curves, factors and other data covering the entire line of Dwyer
Visi-Float' Flowmeters. send for Bulletin F-41.
4.
BULLETIN F 4 3
RATEMASTER@FLOWMETER
DIMENSIONS 8 MOUNTING INFORMATION
DIMENSIONS
- IN INCHES
15-111
/
CUY?
MOUNTING ClAM9
PANEL CUT OUT
(FOR FLUSH MOUNTINGI
n;
4 S/I
DE
111
I )/I6
14/16
15.1/16
2 l/lC
PANEL HOLE SIZES
(FOR SURFACE MOUNTING]
WE
011
1/16
II4
511
Y112
noin
\
1
11/11
11/12
,---
]I 7
t----
- I
-1
C
Figuro 2
1
i
I N L E T PIPING R U N : I t is good practice to approach the
flowmeter inlet with as few elbows and restrictions as possible.
In every case the inlet piping should be at least as large as the
connection to the flowmeter Le. 1/8" lron Pipe Size for RMA,
1/4" IPS for RMB and 1/2" IPS for RMC. Length of inlet
piping makes little difference for normal pressure fed nowmeters.
satisfactory long term service when used with air, water, or
other compatible media. Refer to factory for information on
questionable gases or liquids. Caustic soiutions, anti-freeze
(ethylene glycol) and aromatic solvents should definitely
not be used.
For flowmeters on vacuum air service the inlet piping should
be as short and open as possible. This will allow operation
near atmospheric pressure and thereby insure íhe accuracy of
the device. (Note that for vacuum air service the flow control
valve iI any. should be on the discharge side of the flowmeíer.
Either the T M V unit or a separate in line valve may be
, r?:' .
applied.)
DISCHARGE PIPING: As on the inlet, discharge piping should
be at least as large as the flowmeter connecíion. In addition,
for pressure fed flowmeters on air or gas service the discharge
piping should be as short and open a5 possible Thlr will
allow operation of the flow tube at near atmospheric pressure
and insure the accuracy of the device. This ir of less importance on water or liquid flowmeters since the flowing medium
is generally incompressible and moderate back pressure will
."
not affect the accuracy of the instrument as calibrated.
,
...
. .
POSITION AND MOUNTING All Rate-Master Flowmeters must be mounted in a vertical
position with the inlet connection at the bottom mar and outlet at
e----
top rear.
TEMPERATURE, PRESSURE, ATMOSPHERE, ANDVIBRATION: Rate-hlaster Polycarbonate Flowmeters are exceptionally
tough and strong. They are designed for use at pressures up
to 100 PSI ( R Y B units 70 PSI. RhlC 35 PSI) and temperatures
up to 130 deg. F. DO NOT EXCEED THESE LIMITS! The
installation should not be exposed to strong chlorine atmospheres or solvents such as benzene, acetone. carbon tetrachloride, etc. The mounting panel should be free of excessive
vibration since it may prevent the unit from operating properly.
BEZEL OR THROUGH PANEL MOUNTING: Make &e panel
cutout using the appropriate dimensions from Figure 1. Flowmeter must fit into the panel freely without force or squeeze.
Insert the Rate-Master Flowmeter from the front of the panel
and install the mounting clamps from the rear, insert and tighten
the clamp bolts in the locations shown in Figure 2. Make
connections to inlet and outlet ports using small amount of RTV
sealant or 'Ikflon8 thread tape to avoid leakage. Avoid exeeul
torque which may damage flowmeter body.
-
.
BULLETIN F-43
RATEMASTER" FLOWMETER
Instructkps
-
Figure 3
Figure 4
PAGE 2
Figure 6
Figure 5
Figure 7
-
1. Remove valve knob from RMB or RMC
B V or SSV
units by pulling the knob forward. It is retained by rpring
pressure on the stem half-shaft so that a gentle pull will remove it. On RMA-BV or SSV models, turn the valve knob
counter-clockwise until the threads are disengaged. Then withdraw the stem from the valve by gently pulling on the knob.
2. Remove the four mounting bracket screwr located in the
sides of the flowmeter. See Figure 3.
Pull the flowmeter body gently forward away from the back
plate and pipe thread connections. Kecp the body parallel
with the back plate to avoid undue strain on the body. Lkave
the piping connections intact There ir no need to disturb them.
See Figure 4.
:r
.
3. Remove the slip cap with a push on a screwdriver as rhown
in Figure 5. Remove the plug-ball stop as shown in Figure 6
using allen wrench skgr as followr: Model RWA
1/4', Model
---.RMB
1/2", and Model R M C
3/4.
4. Take out the ball or float by inverting the body aiid allowing the float to fall into your hand as shown in F l g u n 7.
(Note: It la beat to cover the discharge port i o avoid loshg
A
-?..A<
.
the float through that opening.)
" . .,,
-
-
-
-----------
~
8
DO noi completely unscrew valve stem uniest iiowrneter i
r
unpressurized and drained of any IlquM. Removal while in
service will allow gas or liquid to flow wt lront d valve body
and could result in serious personal injury.
'
C L E A N I N G : The how tube and flowmeier body can beat be
cleaned with a little pure soap and water.. Use of a bottle
brush or other soft brush rill aid the cleaning Avoid benzene,
acetone. carbon tetrachloride, alkaline detergent., caurtlc roda,
liquid soaps (which may contain chlorinated rolvmta). dc and
avoid prolonged immersion which may harm o
* .
scale.
REASSEMBLY: Simply reverse Steps SA, 1 through 4 and
place back in service A little stop cock grease or petroleum
jelly on the "O" rings will help maintain a good seal ar well
as facilitate assembly. N o other special care ir rquired.
A?,
1.
Y.
.'
A D D I T I O N A L INFORMATI
For additional flowmeter application information, c&&jon
curves, factorr and other data covering the entire line of Dnyer
RateMaster Flowmetus, send for Bulletin F-41.
56- 440197- 00
u t h o g r m in U.8.A 6/84