Humidity, pressure and carbon dioxide measurement For Low

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Humidity, pressure and
carbon dioxide measurement
The New Vaisala DMT242
Dewpoint Transmitter
For Low Dewpoint OEM
Measurements
Vaisala’s ppm Calculation
of Moisture in Transformer Oil
Using the HMP228
Transmitter
PTB210 Series Digital Barometers
For Measuring in
Extreme Environments
Outdoor Plant Growth Experiments
In the Elevated CO2
Atmospheres in Japan
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Contents
Presidents’ Column
3
Dewpoint
Low Dewpoint OEM Measurements
Humidity Expressed as Dewpoint Temperature
U.S. National Weather Service Awards
Dewpoint Contract to Vaisala
4
6
8
Humidity
Industrial Humidity Measurements
Reliable Performance in Humid Air
Conditioning Applications
Improved Maintenance for Transformers
Using Automated Long-Term
Monitoring of Relative Humidity
Vaisala Sensor in Radio Telemetry
Instrumentation Systems
8
10
11
13
16
Pressure
Reliable Barometric Pressure Measurement
in All Wind Conditions
PMI20 Digital Barometer Display
- Perfect Partner for Vaisala’s Barometers
Measuring for Extreme Environments
Using PTB210 Barometers
Meteorological Service of Canada:
Digital Barometers at Airport Locations
Vaisala’s Barometers Used to Track
Leakage from Nuclear Enclosures
Vaisala has been awarded a
contract by the Meteorological
Service of Canada (MSC).
Vaisala supplies electronic
station barometers to replace
the mercury barometers
currently used for weather
observation throughout
Canada. The PTB220 digital
barometer is easy to maintain,
and can be exposed to
extremes of temperature
between -20 and +60 °C.
18
20
21
22
24
Carbon dioxide is used to
carbonate the beverages in the
production of soft drinks. In
the United States, OSHA
requires that the carbon
dioxide level remains at, or
below, 5,000 ppm in the
atmosphere of any filler room
area. Big Springs Inc. is a
major soft drink manufacturer
and a large local Coca-Cola
franchise distributor located in
Huntsville, Alabama. The
company has successfully used
Vaisala CARBOCAP
transmitters for more than a
year in their bottling plant.
Carbon Dioxide
Dissolved CO2 Measurements
GMM220 Series Carbon Dioxide
Measurement Module
Measuring Carbon Dioxide in the
Soft Drinks Industry
GMT220 Series Industrial Carbon
Dioxide Transmitter
Outdoor Plant Growth Experiments
in Elevated CO2 Atmospheres
24
26
27
28
29
Others
Services and Calibration at Standard Prices
Meeting the Demands of the Customer
32
34
Vaisala in Brief
– We develop, manufacture
and market products and
services for environmental
and industrial measurements.
– We focus on market segments where we can be
world leaders, the preferred supplier. We pay
high attention on customer
satisfaction. Our main qual– Purpose of those meaity discipline is Product
surements is to provide
Leadership. Competitive
basis for better quality of
advantage is enhanced by
life, cost savings, protection economies of scale and
of environment, improved scope.
safety and performance.
2
154/2000
The Vaisala After Sales Service
for humidity, barometric
pressure and carbon dioxide
products in Europe has
increased its range of services.
In addition to service and
repair facilities, our European
Service Center offers factory
calibration facilities to
customers in Europe, Israel
and South Africa. The first
parameter in this factory
calibration service is relative
humidity.
Cover photo:
Jussarö Lighthouse, Finland
Finnish Maritime Administration.
Editor-in-Chief:
Marit Finne
Publisher:
Vaisala Oyj
P.O. Box 26
FIN-00421 Helsinki
FINLAND
Phone (int.):
+358 9 894 91
Telefax:
+358 9 894 9227
Internet:
www.vaisala.com
Design and Artwork:
Non-Stop Studiot Oy
Editors:
Bellcrest Language
Services Oy
Printed in Finland by
Sävypaino, Finland
ISSN 1238-2388
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President’s Column
■■■
Environmental
Measurements for
a Variety of Needs
V
aisala’s Sensor Systems Division (SSD)
specializes in a few
selected parameters
of environmental measurement. These are many forms of
humidity, barometric pressure
and gas measurements, selectively. We manufacture this
type of equipment for demanding users, for use in various applications to improve productivity, quality and safety.
Our aim has been to constantly expand our product range to
meet varying new requirements.
Humidity measurement solutions already include hundreds
of applications. However, the
same product is not suited to
every environment. Recently, we
have launched new products especially for measuring low humidities, where the unit of measurement is the dewpoint. Besides
traditional HUMICAP® technology, we have developed the
new DRYCAP® technology.
Moisture measurement in transformer oil is also a new area of
application. The presence of
moisture in liquid transformer
insulation plays a critical role in
the life of a transformer. Detecting moisture in oil is an essential
part of a comprehensive transformer maintenance program.
Many Meteorological Services
are entering a new era of air humidity measurement and the
U.S. National Weather Service is
one of the pioneers in this area.
Delays in measuring data, even
in situations where the weather
changes quickly, can be eliminated thanks to the new method.
Through Vaisala’s BAROCAP® technology, barometric
pressure measurement has reinforced its firm standing among
professional meteorologists.
Producing and using carbon
dioxide is fundamental for living
organisms. To optimize living
conditions for flora and fauna,
the correct concentration of carbon dioxide is essential. Levels of
carbon dioxide that are too high
can be hazardous, even dangerous, so reliable measurement
and stability are important. In
this respect, Vaisala’s CARBOCAP® technology has been
given the approval of the experts.
Measuring instruments are a
part of our customers’ processes.
In order to maintain high quality processes that can even be
certified, measuring instruments must be well maintained.
Instruments need to be calibrated at regular intervals in order
to guarantee that operations are
of high quality. We have developed our own operations to be
able to better face this challenge.
We are already developing
technology for working with
new gases and developing associated technology. Through these,
in the future, we will be able to
offer even more measurements
for improving productivity and
safety.
■
Pekka Ketonen
President and CEO
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New DMT242 dewpoint transmitter for
Low Dewpoint OEM Measurements
Vaisala has launched a transmitter for low dewpoint OEM measurements with unparalleled
long term stability! One of the main assets of
DRYCAP® technology is its excellent long term
stability, and the new DMT242 incorporates
DRYCAP® polymer technology.
Jan Grönblad, M.Sc. (Eng.)
Product Manager
Sensor Systems Division
Vaisala Helsinki
Finland
T
he latest addition to
our dewpoint product range is the
DMT242 transmitter, which is based on
DRYCAP® low dewpoint, thin
film polymer technology. The
new product is geared towards
OEM manufacturers, who are
looking for a dewpoint transmitter with low maintenance
needs, that is simple to install
and use, but who also expect the
high reliability that is synonymous with the Vaisala brand.
The Vaisala DMT242 dewpoint transmitter is an ideal
choice for industrial applications where it is necessary to
control the dryer performance
in low dewpoints. The transmitter provides wide dewpoint
temperature
measurements
ranging from –60 °C to +60
°C, with an accuracy of ±2 °C.
DMT242 – a product
with excellent long
term stability
The Vaisala DMT242 dewpoint
transmitter is an ideal choice for
industrial applications where it is
necessary to control the dryer
performance in low dewpoints.
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The DMT242 dewpoint transmitter was developed with the
needs of OEM type manufacturers firmly in mind, because
they require a very basic meas-
urement instrument that uses
the kind of technology that
would not require the end user
of the equipment to carry out
much maintenance. Until now,
the need for high maintenance
has mainly been due to the
long-term drift, which has
forced the end user to carry out
maintenance on their drying
systems, e.g. on a compressed
air dryer, as often as twice a
year, in order for the drying system to maintain its high performance specifications.
In 1997, Vaisala launched a
patented technology for low
dewpoint measurements, incorporating the DRYCAP® sensor
in a DMP248 dewpoint transmitter that had a wide range of
features. The main advantage
of the DRYCAP® technology is
its excellent long term stability.
The improvement is largely
due to the fact that a polymerbased sensing material was chosen, rather than the sensing
technology that was already on
the market.
Polymer itself is a very stable
material. A polymer sensor also
makes it possible for so-called
autocalibration to be performed at certain intervals. This
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basically means that, during autocalibration, the polymer is
warmed so that it is slightly
above the surrounding temperature and, based on widely recognized physical changes, the
dry end (i.e. offset) error in the
sensor response can be detected
and eliminated. The capacity to
correct the offset error makes
the polymer technology a highly competitive technology for
low dewpoint measurements.
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Dew resistance
The DMT242 dewpoint transmitter
incorporates the DRYCAP polymer
sensor.
Another advantage is that polymer technology is dew resistant, should condensation be a
possibility. Also, exposing a
sensor to normal ambient air
for longer periods – even to
laboratory air – can be as fatal
as a high humidity exposure for
some low dewpoint sensors.
When installed inside in a drying system, high humidity levels are not usually a problem,
but they can still be a potential
threat during startup of the drying system or during a drying
system malfunction.
If dew forms on the sensor
element, the DRYCAP® sensor
fully recovers after it has dried
out, and no recalibration is
needed. Full recovery means
not only that process downtime that would be caused by
maintenance is avoided, but
also means direct savings in recalibration and sensor replacement costs. Also, storage in
normal ambient air does not
pose a problem because polymer technology is one of the
most common technologies
used for controlling indoor air
humidity in offices, cleanrooms and production areas.
The new DMT242 dewpoint
transmitter has all of these assets
thanks to the DRYCAP® polymer technology that it incorpo-
rates. The number of transmitter options has been minimized
to allow for a very cost effective
product, but which nevertheless
provides high measurement performance. It is, however, easy
and quick to install or replace
the DMT242 as it comes with
the IP65/NEMA4 protected
connector with screw terminals,
as standard. For maintenance
purposes, the unit also comes
equipped the RS232 serial line,
making it possible for the user
to rescale the analog output
with a standard PC.
The DMT242 product fulfils
low dewpoint measurement requirements in a wide variety of
OEM applications including
compressed air, electronics,
plastics, metal, as well as in
other industries. The experience gathered in a wide variety
of applications in these industries has shown the DRYCAP®
measurement technology to be
a superior in performance. ■
Electrical connection of the DMT242
dewpoint transmitter is fast and easy
thanks to its connector.
P H O T O C O U R T E S Y O F AT L A S C O P C O .
Dryers and other OEM applications are the typical environment for DMT242 dewpoint transmitter.
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Dewpoint is one of
the many widely used
parameters alongside
relative humidity, absolute humidity, mixing ratio and partial
water vapor pressure,
that show the water
vapor content in air or
in other gases. The following article explains
the behavior of dewpoint temperature (Td)
and clarifies the terminology used to describe it.
Humidity Expressed as
Dewpoint Temperature
D
Senja Paasimaa, M.Sc. (Eng.)
Product Engineer
Sensor Systems Division
Vaisala Helsinki
Finland
6
154/2000
ewpoint is defined as
the temperature (°C
or °F) to which air
must be cooled for
water condensation to begin,
i.e. for air to become saturated
with water vapor. At dewpoint
temperature, the amount of
water vapor present in the air is
equal to the maximum amount
of vapor air can hold at that
specific temperature.
The capacity of air to hold
water vapor is strongly dependant on temperature; warmer
air can hold more vapor. This
phenomenon is usually illustrated with a curve with water
vapor saturation pressure as a
function of temperature (Figure
1). At dewpoint, the partial
water vapor pressure (Pw) in air
equals the water vapor saturation pressure (Pws). In this state,
condensation and evaporation
are in equilibrium and take
place at the same rate.
Since the correlation between water vapor saturation
pressure and temperature is
known, the dewpoint can be
calculated from the measured
temperature and the relative
humidity (Figure 1). This principle is used by some instruments with capacitive sensors
to measure dewpoint in a gas.
A practical example of dewpoint is a glass of cold liquid
on a warm summer day. If the
temperature of the drink is
equal to, or below, the dewpoint of ambient air, the air
close to the glass surface cools
down and becomes saturated
with water vapor that condenses on the surface, forming
water droplets called ‘dew’.
Temperature changes
According to its definition,
dewpoint is related to the
amount of water vapor, i.e. the
partial water vapor pressure,
and is thus not dependant on
temperature. This means that
the dewpoint of a process with
high temperature is equal to
the dewpoint measured from a
cooled sample of that process
gas. However, if the gas sample
is taken from the process to an
environment where the temperature is below the process
dewpoint, a dew formation ap-
pears, and this results in an inapplicable measurement.
Pressure changes
Dewpoint is a pressure sensitive
parameter, because variation in
total pressure changes the partial water vapor pressure according to Dalton’s law:
Ptotal=Pw+Pdry air,
Where the total pressure is
the sum of the partial pressures
of the gas components present:
water vapor and dry air.
Pressurized air provides a
practical example of what happens if the air at +20 °C is compressed from atmospheric pressure to a pressure of six bar
(6000 hPa). We assume that the
dewpoint of ambient air is +6°C
(Pw=9.35 hPa), and that the
temperature remains constant
during compression. As the air
is compressed, the partial water
vapor pressure (Pw) is increased
sixfold to Pw=56.1 hPa. The calculated dewpoint would then be
+34.9 °C. However, dewpoint is
always less than, or equal to am-
08:36
Sivu 7
used. The water vapor saturation pressure over ice is slightly
lower than that over supercooled water, i.e. ice gives off
water vapor at lower rate (Figure
2). This must be taken into account when using a measurement technology in which the
dew/frostpoint is a calculated
parameter derived from relative
humidity or from the partial
water vapor pressure. As frost
forms, it always occurs at a frostpoint that is different to dewpoint.
As in the case of dewpoint,
the frostpoint can also be seen
in practice by taking a package
from a freezer to room temperature. In this case, the air close
to the package cools down and
becomes saturated with water
vapor, which forms frost instead of dew, on the package
surface.
Why dewpoint?
bient air temperature. Thus,
dew formation would take place
until the partial water vapor
pressure is equal to the water
saturation pressure at that temperature (23.4 hPa) i.e., dewpoint is the same as the actual
air temperature, +20 °C.
Conversely, if a sample was
taken from pressurized air
(6000 hPa) with dewpoint of
+3 °C to an atmospheric pressure of 1000 hPa, the dewpoint
would then be –20 °C.
When using a measurement
technology that cannot be installed in the pressurized
process, but a sampling system
is needed, the dewpoint in the
process, which is sometimes
called pressure dewpoint, has
to be calculated from the measured value. However, new technologies have enabled measurements straight from the
pressurized processes, thus obviating the troublesome logarithmic calculations.
Dewpoint or frostpoint
If dewpoint is below zero (0 °C),
the term frostpoint (Tf) is often
Dewpoint is a commonly used
parameter to represent the
amount of water vapor in dry
applications such as pressurized air systems. In dry conditions, changes in dewpoint values are much larger compared
to very small changes in relative humidity values, which
gives dewpoint measurements
an advantage in process control. For example, at room temperature, change in dewpoint
from –40 °C to –45 °C corresponds to relative humidity
from 0.81 % RH to 0.48 % RH.
In applications where gas
pipes are installed outdoors,
dewpoint is a useful parameter,
because of wide variations in
ambient air temperature. The
gas should be dried to such a
high degree that dew formation
is avoided regardless of the
temperature in the pipe, which
means that dewpoint of the gas
should be below the gas temperature in all conditions.
Chilled mirrors
One traditional method to measure dewpoint is a chilled mirror
instrument where the mirror is
cooled down until dew forms
on it. The dew formation causes
light to be scattered on the surface, and this is detected with
optics. At the start of dew formation, the temperature of the
mirror denoting dewpoint is
read by a thermometer.
1200
1000
Pws (hPa)
13.9.2000
800
600
at 60 °C
RH = 100%
P ws = 198 hPa
Td = 60 °C
400
T = 80 °C
RH = 42 %
P w = 198 hPa
200
0
0
10
20
30
40
50
60
70
80
90
100
Temperature (°C)
Figure 1. Water vapor saturation pressure Pws as a function of temperature.
Dewpoint of a gas at 80 °C and 42 % RH.
800
600
Pws (Pa)
40234Ymi_Vaisala154
400
T = 0 °C
RH = 20 %
200
Td = -20 °C
Tf = -18 °C
0
-40
-20
-20
-10
0
Temperature (°C)
Figure 2. Water vapor saturation pressure Pws over water (—) and ice (- - -).
Dewpoint and frostpoint of a gas at 0 °C and 20 % RH.
This fundamental measuring
technology is widely used as a
calibration reference in laboratories because it gives very accurate results over a wide range
of dewpoints. However, it cannot tolerate dusty environments due to its sensitive optics, and thus it is less commonly used for process control
purposes.
With a chilled mirror instrument, dew, rather than frost,
may also occur below freezing
point, even down to –20 °C.
Before frost, dew forms due to a
lack of impurities on a very
clean surface initializing the
crystallization. This must be
noted when comparing the readings of instruments using different technologies such as capacitive instruments, in which relative humidity or the partial
water vapor pressure are the variables measured initially. The differences in the readings of the
instruments may be due to the
fact that one actually shows dewpoint and the other, frostpoint.
Capacitive instruments
Metal oxide sensors have been
widely used in industrial processes for the past three decades.
They have proved to be suitable for on-line measurement
and tolerate dusty environments better than chilled mirrors. However, their poor longterm stability means there is a
need for frequent calibration,
which increases maintenance
costs. Moreover, relatively high
humidity may destroy the sensor e.g. if there is a drier malfunction in the process, or even
during a system ramp up.
Recently, polymer sensors
have also been introduced to
dewpoint applications. Their
advantages over the metal oxide
sensors are that they tolerate
condensing water and have far
better long-term stability. The
accuracy of polymer sensors has
recently been improved to such
a degree that they are reliable in
applications with low dewpoints,
even down to –70 °C.
■
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Jan Grönblad, M.Sc. (Eng.)
Product Manager
Sensor Systems Division
Vaisala Helsinki
Finland
Vaisala’s HMP243 dewpoint transmitter has specially designed for
reliable and fast dewpoint measurement.
U.S. National
Weather Service
Awards Dewpoint
Contract to Vaisala
T
he U.S. Department of Commerce/NOAA,
National Weather Service (NWS) has awarded a
contract to Vaisala to develop and manufacture a
state-of-the-art meteorological dewpoint sensor.
This sensor will replace several hundred aging and high maintenance units originally installed in Automated Surface
Observing Systems (ASOS) at major airports throughout the
United States.
NWS selected Vaisala after more than three years of extensive testing of standard off-the-shelf dewpoint instruments manufactured by Vaisala and its competitors. Vaisala’s
HMP243 dewpoint transmitter was the unit tested by NWS,
and the core technology of this transmitter will be incorporated into the sensors to be delivered to NWS.
Vaisala’s HMP243 humidity/dewpoint transmitter provides fast and reliable dewpoint measurement even under extreme conditions where a combination of high humidity and
rapidly changing temperature might present unwanted dew
formation on the sensor head. Because the temperature of
the HMP243’s sensor head is constantly higher than ambient, the possibility of dew formation is eliminated. The result
is uninterrupted, accurate and stable dewpoint measurement
that is unmatched by other technologies.
■
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Many industrial environments set specific requirements for humidity instrumentation.
The latest addition to the Vaisala range of industrial humidity transmitters is a small stainless steel sensorhead. It offers many new advantageous features for applications where a
robust sensorhead is required. The new transmitter models HMP237 and HMP247, incorporating the new sensorhead structure, are already available.
Focus on reliable readings
Measuring humidity in demanding environments is not an easy
task.
First, the measurement technology used must be applicable
for the particular environmental conditions in a specific application. One technology may
offer certain features for good
measurement, but maintenance
needs can be very high. Not all
the instruments offering the
same technology have the ability to provide reliable readings
in high temperatures, very high
levels of humidity approaching
condensation, or in certain environments where chemicals
are present in the measured gas.
Second, the mechanics of the
instrument, and especially
those of the sensorhead are extremely important in demanding applications.
HMP237/247
sensorhead technology
In industrial applications, the
transmitter housing must be
IP65/NEMA4 protected, to
allow for plants to be spray-watered, for example. The housing material can be plastic or,
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HMP247 humidity transmitter uses the recently
developed small-sized metal sensorhead for the
most demanding applications.
Two threaded holes
on the back of the
sensorhead mean
that the sensorhead
can be installed in
process conditions.
Managing demanding customer needs in
Industrial Humidity Measurements
in demanding environments,
metal. The sensorhead mechanics are a little more complicated, because the most essential part of the entire instrument is located in the sensorhead. If the mechanics and the
sensor protection are not well
adapted to the particular environment that they are in, the
entire measurement can be impaired or the lifetime of the instrument can be reduced.
The new small-sized, extremely robust sensorhead was
developed for the most demanding customer needs. The
sensorhead was first used in the
HMP230 series, and the transmitter model was then called
the HMP237. Later, the same
structure was developed and
also added to HMP240 series
and called the HMP247.
The main difference between
these two series, the HMP230
and HMP240, is that the
HMP240 series sensorheads incorporate a warming system,
which ensures reliable measurements even in conditions where
dew may form. This warming
method is patented by Vaisala.
Both of these sensorhead types
can be used in very high temperatures of up to +180 °C
(+356 °F).
means that it can be installed in
different ways. On the back of
the sensorhead, two threaded
holes allow it to be fixed to a
threaded pole inside the process and thus to be usefully located right in the heart of a particular place, if needed.
The new installation options,
a design adapted to tough environments and high performance humidity sensing with
HUMICAP sensors make the
HMP237 and HMP247 a very
attractive choice as industrial
humidity transmitters.
■
Leak tight installation
The material of these new sensorheads is stainless steel, a material suitable for a wide variety of
applications. The robust nature
of this sensorhead is not its only
asset, because it is also leak tight
up to 1 Mpa (10 Bar/145 Psi). The
leak tight installation can be fitted around the sensorhead, but
also on the sealing around the
sensorhead cable, making the installation very flexible in applications where the pressure of the
measurement space differs from
the ambient pressure.
In addition to the traditional
duct installation kit, the design
of the new sensorhead also
A leak tight installation is possible for the sealing around the sensorhead cable,
but naturally also for sealing the connection around the metal body of the
sensorhead.
Process wall
Installation b)
Process wall
Installation a)
Maximum pressure 1 MPa
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The HMW61 & HMW71 Humidity Transmitters
Reliable Performance in Humid
Air Conditioning Applications
In response to concerns about efficient
air conditioning and
economical solutions,
reliable humidity measurement instruments
play a key role in
monitoring humidity
levels in dusty and
moist environments.
For example, ventilation in environments
such as greenhouses
and indoor swimming
pools is a challenge
for humidity control
instruments. Vaisala’s
new wall-mounted
HMW61 & HMW71
transmitters are specifically designed for such
demanding air conditioning applications.
10 154/2000
T
he HMD/W 60/70
series, Vaisala’s range
of humidity and temperature transmitters
for air conditioning applications, has been enlarged with
new additions – the wall mounted HMW61 & the HMW71
transmitters. They are designed
for dusty and humid air-conditioning applications where accurate and stable measurement
and control of relative humidity
and temperature are required.
Wall-mounted HMW61 & HMW71 transmitters are designed for dusty and
humid air-conditioning applications, such as indoor swimming pools.
Protection against dust
and water spray
The transmitters are dust and
water spray resistant and meet
IP65 (NEMA 4) requirements.
All the materials used have been
chosen for their excellent corrosion resistance. This makes the
transmitters especially suitable
for humid and wet environments. Applications include
greenhouses, livestock farms, indoor swimming pools, various
types of storage area and any
other areas, which are regularly
cleaned with sprayed water.
The HMW61/71 transmitters
are available either with humid-
ity measurement only (U models) or with both humidity and
temperature measurement (Y
models). The HMW61 has current output (loop-powered)
and the HMW71 has voltage
output, where different voltage
scales can be selected with
jumpers.
Fast, on-site calibration
The output of the HMW61/71
transmitters can be easily
checked at the place of installation while still operating, using
the HMI41 humidity indicator
with a field calibration option.
Any adjustment required can
be made within seconds without de-installing the transmitter
or interrupting the measurement. This feature makes maintenance easy, rapid and cost effective. Alternatively, the
HMK15 humidity calibrator
can be used for calibrating in
various levels of humidity.
The transmitters incorporate
the HUMICAP®180 sensor,
which has excellent stability
even in high levels of humidity.
The sensor is also insensitive to
dust and most chemicals.
■
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Vaisala’s ppm calculation for moisture in transformer oil
Improved Maintenance
for Transformers
Vaisala’s microprocessor-based HMP228 transmitter enables
continuous moisture and temperature measurements in transformer oil.
The presence of moisture in liquid transformer insulation
plays a critical role in
the life of a transformer. Determining
the amount of moisture in oil is an essential part of any comprehensive transformer
maintenance program.
The Vaisala microprocessor-based
HMP228 transmitter
enables continuous
moisture and temperature measurements in
transformer oil.
Irma Ylikangas,
M.Sc. (Chem. Eng.)
Product Manager
Sensors Systems Division
Vaisala Helsinki
Finland
E
xcessive
moisture
content in oil makes
the insulation materials age more quickly and reduces their dielectric
strength. In general, the mechanical life of insulation is reduced by half every time that
the water content is doubled.
The rate of thermal deterioration of the paper is proportional to its water content.
continues…
The presence of moisture in liquid transformer insulation plays a critical role in the life of a transformer.
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08:51
Sivu 12
Water in mineral oil transformers creates the risk of bubble formation, when desorption
of water from the cellulose increases the local concentration
of gases in the oil. Accurate
moisture measurements can
also provide warning of leaks in
the oil systems, as the water is
absorbed from the surrounding
air.
Reliable sensors
technology
The HMP228 transmitter incorporates the latest version of
the Vaisala capacitive thin film
polymer sensor.
It operates by measuring
changes in its capacitance as
the thin film absorbs water
molecules from the oil.
Principle measured and
calculated values
HMP228 identifies
servicing requirements
In the electrical industry, moisture measurements indicate the
condition of transformer oil
and identifies servicing requirements. This HMP228 Moisture
and Temperature Transmitter,
improves the maintenance of
transformers, and enables reliable and continuous measurement of their transformer oil
moisture and temperature. ■
12 154/2000
Moisture levels in oil are affected by temperature cycling of a transformer. The extent
to which oil is water soluble is dependant on temperature: the more the temperature
rises, the more soluble it is.
20
18
Maximum error of the reading (%)
Water activity is the principle
measured value. Water activity
immediately indicates whether
the oil is too moist. The measurement remains proportional
to the saturation level of water
in each individual oil, independent of the aging or temperature of the oil.
Traditionally, the transformer field has used ppm values. Thus, Vaisala offers the
Calculation
Model
with
Average Coefficients for mineral transformer oils and the
Calculation Model with Oil
Specific Coefficients for mineral and silicon based oils. All silicon based transformer oils
need to use the Calculation
Model with the Oil Specific
Calculation Model.
16
14
12
10
8
6
4
2
0
0
10
20
30
40
50
60
70
80
90
100
Temperature (deg C)
The maximum number of errors caused by deviation of mineral oils using
Average Calculation Model.
40234Ymi_Vaisala154
13.9.2000
08:51
Sivu 13
Terry Willems
Senior Materials Scientist
and
Howard Kanare
Principal Scientist
Construction Technology
Laboratories Inc.
Skokie, IL, USA
Figure 1. CTL staff have been using
Vaisala’s HMI41 hand-held
moisture meters and HMP44
measurement probes for relative
humidity measurement in concrete
slabs.
Investigating floor moisture problems
Using Automated Long-Term
Monitoring of Relative Humidity
In recent years, CTL has focused on the problems caused by excessive moisture in floors. To
investigate moisture problems affecting floor
coverings in buildings, CTL staff have been
using Vaisala’s HMI41 hand-held moisture meters and HMP44 measurement probes for relative humidity measurement in concrete slabs.
S
ince 1993, Construction Technology Laboratories, Inc. (CTL)
staff have become increasingly involved in troubleshooting moisture problems
in concrete floors with moisture-sensitive floor coverings.
Resilient floorings such as vinyl
sheet, vinyl composition tile,
linoleum, and vinyl-backed carpet are all susceptible to problems when excessive moisture
and alkalies from concrete
react with adhesive or cause
plasticizer breakdown.
Professional solutions
Since many of the projects we
evaluate are a considerable dis-
tance from our home office, the
hand-held meter requires separate trips to the jobsite. We
need to drill holes and place
probes, then a return trip to
take readings at least three days
later after the probes have equilibrated in the concrete. To reduce travel costs and to collect
more detailed data, we decided
to begin using automated data
logging instruments and to
leave probes in place for several
months.
Data logging of relative humidity levels in the concrete
provides a method to obtain
accurate readings and to track
changes with time. Calibrated
probes are installed into the
drilled concrete holes. The
154/2000 13
40234Ymi_Vaisala154
13.9.2000
08:51
Sivu 14
The authors of the article: Howard Kanare (left) and Terry Willems.
14 154/2000
Revealing RH results
Two useful results came from
the data collected over two
months. First, the results (see
Figure 5) indicated that in the
area of distressed carpet on the
slab-on-ground, moisture levels
were very high, averaging about
97 % RH at two-inches (50
mm) below the top of the slab.
WEST
1999 and began to maintain a
steady internal RH after that
date. By contrast, the elevated
slab continued to dry at a fairly
constant rate. (The steep rise in
the curves seen from 2–6
November is due to the probes
reaching equilibrium with the
surrounding concrete which
takes 3–4 days after placement.)
Cost-effective approach
to monitoring
Upon excavation of a portion of
the concrete floor, we determined that the granular layer directly below the slab contained
7 % moisture (by weight), sufficient to replace the moisture
lost from drying the slab during
construction, before flooring
was installed. We calculated that
the slab-on-ground would take
many years to dry sufficiently
for moisture-sensitive floor coverings. Therefore, we recom-
EAST
5
1A 1B 1C
2A 2B 2C
LIGHT WEIGHT
CONCRETE
METAL DECK
5”
Vinyl-backed carpet tiles had
been installed in a medical facility on two concrete substrates: a slab-on-ground and
an adjacent elevated lightweight concrete slab cast on
ribbed steel deck. Carpet tiles
installed on the elevated lightweight concrete were wellbonded and did not exhibit
distress. However, carpet tile
was curling and debonding on
the slab-on-ground. The slabon-ground consisted of a 5inch (125-mm) thick, normal
weight concrete slab cast on 7inch (175-mm) sand layer on
top of an 8-mil (0.2-mm) plastic vapor retarder. The vapor retarder sheet should have kept
moisture from entering the
floor system from below, but
moisture was somehow getting
to the underside of the carpet
through the concrete. Vaisala
HMP44 relative humidity
probes were selected to study
the situation.
CTL placed HMP44 probes
in six locations, three in the
slab-on-ground and three in
the lightweight concrete slab
(see Figure 2). Six probes were
‘match calibrated’ together to
provide the best possible preci-
By contrast, the elevated slab
had 70–75 % RH at the same
depth. Humidity below 85 % is
generally considered acceptable
for floor coverings. Above this
level a host of problems can
occur, including mold and
mildew, adhesive degradation,
plasticizer breakdown, and dimensional changes of flooring
such as curling and shrinkage.
These forms of distress cause
maintenance problems and can
lead to trip-and-fall hazards.
A second result from the data
was knowledge that the elevated slab was drying while the
slab-on-ground was actually becoming wetter, even though
the floor was nearly two years
old! The data indicated that the
concrete slab-on-ground was
reaching equilibrium with the
wet sand below.
The Figure 5 shows the slabon-ground was gaining moisture until the end of November
2”
Thorough studies of
vinyl-backed carpet tiles
sion. The probes were placed at
depths of 1, 2, and 3 inches (25,
50, and 75 mm) and connected
to an ACR SmartReader Plus
seven channel data logger. This
compact, self-contained logger
has a 10-year lithium battery
and can be unplugged from the
data collection system and
mailed to our laboratories for
downloading data. Humidity
readings were averaged every
eight seconds and recorded
once every hour for approximately two months.
3,5”
probes are linked to a data logger that reads, averages, and
records the relative humidity at
preset intervals up to many
months.
VAPOR RETARDER
(PLASTIC SHEET)
Figure 2. CTL placed Vaisala’s
HMP44 probes to six locations, three
(2A, 2B, 2C) in slab-on-ground and
three (1A, 1B, 1C) in the lightweight
concrete slab.
2
SECTION
NTS
NORMAL WEIGHT
CONCRETE
7” SAND LAYER
40234Ymi_Vaisala154
13.9.2000
08:51
Sivu 15
Figure 3. A typical problem of adhesive failure
caused by excessive moisture in concrete. Some
water-based adhesives are re-emulsifiable and can
become gummy losing adhesion between the concrete
and the vinyl-backed flooring.
mended to the facility owner
that the existing flooring should
be replaced with less-moisturesensitive flooring.
Data logging wiring cannot
be installed everywhere in a
building due to the traffic patterns, uses of the facility, and
cost. In addition to logging
with several probes, we also
placed probes in several remote
locations throughout affected
areas of the building and read
those with the HMI44 handheld meter. Results of the monitoring program indicated potential problems existed in
other parts of the building as
well. After reviewing the data,
the construction contractor
agreed to replace the carpet
tiles with a more breathable
floor covering and monitor the
building for future problems.
We presented the findings to
a meeting of architects and
construction contractors who
were able to see graphically
how moisture was moving into,
and out of, the floors they had
built. They learned a valuable
lesson about how to prevent
this sort problem from occurring by careful architectural detailing in new construction.
Important
investigative tool
The combination of accurate
relative humidity measurements
and long-term monitoring is an
important tool for investigating
floor moisture problems. Now,
we can document drying history, look for changes due to ambient conditions, relative differences between different portions of the building, and predict slab drying times.
The amount of data recorded results in a high level of confidence in our predictions. By
establishing moisture profiles
within the slab, trends are easily seen. While monitoring of
concrete relative humidity is
just one part of our investigation, the advantages of data
logging has led us to new understanding of long term moisture levels within concrete. ■
Figure 4. Carpet tile was curling and debonding on
the slab-on-ground.
Relative Humidity in Carpeted Concrete Floor Slabs
50
55
CTL – Professional
solutions for moisture problems
1-inch
Relative Humidity, percent
60
65
70
2-inch
suspended slab
on metal deck
75
80
3-inch
85
1-inch
90
95
100
30-Oct 6-Nov 13-Nov 20-Nov 27-Nov
2,3-inch
slab-on-ground
Construction Technology
Laboratories, Inc. (CTL)
perform research, testing
and consulting on a wide
range of construction materials. With a 75-year
history, CTL is known
worldwide for its solutions of construction or
performance problems.
The company has its
main office and laboratories in Skokie, Illinois, with
130 staff, including
chemists, geologists, ceramists, architects and
civil and structural engineers.
4-Dec 11-Dec 18-Dec 25-Dec 1-Jan
Figure 5. Results of data collected over two months, related to relative humidity is carpented concrete floor slabs.
154/2000 15
40234Ymi_Vaisala154
13.9.2000
08:51
Sivu 16
Vaisala Sensors in Radio Telemetry
Instrumentation Systems
Hanwell Instruments specializes in radio telemetry systems for monitoring
and control in a wide range of environments, ranging from historic buildings to industrial processes. Since 1998, the company has used Vaisala humidity sensors for all relative humidity monitoring due to their stability
and rapid response characteristics. Vaisala’s carbon dioxide sensors are also
incorporated in a Hanwell transmitter unit for measuring carbon dioxide
gas concentration.
H
anwell Instruments
Ltd. was established
in 1990 and is based
at two sites in
Southern England. The company specializes in radio telemetry systems for monitoring and
control in a wide range of environments. The applications
range from historic buildings to
industrial processes. Hanwell is
using Vaisala humidity and carbon dioxide sensors in their
radio telemetry applications.
Radio telemetry and
data logging systems
Hanwell’s relative humidity and temperature Radiolog transmitters with the base station receiver and computer. Since
1998, Hanwell has used Vaisala’s humidity sensors for all humidity monitoring due to their stability and rapid response
characteristics.
16 154/2000
Accurate sensors are, of course,
a vital component of any measurement system but the practicalities of data collection and
presentation are of equal importance. Where continuous
monitoring is necessary, this
task is traditionally performed
by hard wiring sensors back to
a central data collection point
or by using stand-alone data
logging equipment. Both approaches can have their disadvantages in specific applications.
Stand-alone data loggers require regular human intervention and this inevitably leads to
a variety of problems, especially if logging is required at remote sites. Lost or corrupted
data can be expensive and time
consuming to rectify. Wired
systems are better. However, on
sites where cables can be easily
damaged or regular changes
need to be made, the connection and re-routing of cables
can be a problem. Indeed in
many circumstances it may be
impossible or very expensive to
install cabling in the first place.
Radio telemetry systems
offer a solution in principle to
many of the problems outlined
40234Ymi_Vaisala154
13.9.2000
Dr. Martin Hancock
Technical Director and
Founder of
Hanwell Instruments Ltd.
United Kingdom
above, but, in practice, users of
such systems have often been
disappointed. There are many
reasons for this, the most important being that the radio
telemetry link has traditionally
been designed independently
from the sensors, logger and
data processing software.
Hanwell Instruments have
taken a holistic approach to the
design of the telemetry sensor
systems. The radio transmitter
is fully integrated with the sensor technology and robust error
correction software ensures the
integrity of data.
Monitoring for
optimum conditions
The Hanwell system was originally designed for monitoring
the environment in historic
buildings, museums and galleries, where optimum conditions have to be maintained to
preserve valuable artifacts, paintings and the internal fabric of
the building. Accurate control
of such variables as relative humidity, temperature and light
levels is vital. In such applications sensors must be unobtrusive and capable of mounting in
different locations, because layouts often change.
08:51
Sivu 17
Due to the historic nature of
these buildings wiring is often
impossible or prohibitively expensive. The size and substantial
construction of these buildings
can also affect the quality of
radio links, but Hanwell technology has overcome these
problems. It is now used in
many of the world’s major cultural institutions including the
Louvre and the British Museum.
The Hanwell Radiolog
system and Vaisala
sensors
The Radiolog telemetry system
has many enhanced software
and calibration features and is
now being used in a diverse
range of applications. Increasingly, customers need verifiable
humidity and temperature sensors for use in a wide range of
operating conditions. Over the
years, Hanwell has evaluated
many manufacturers of humidity sensors, but since 1998 has
used the Vaisala Humichip and
is very happy with its performance and reliability. The
telemetry sensor transmitter is
battery powered, so low power
consumption is important.
When readings are taken the
sensor has to be capable of accurate measurement after a very
short warm up period. This,
combined with the sensor stability, makes the Humichip an
ideal choice for the Radiolog
system.
Hanwell also uses the Vaisala
carbon dioxide CARBOCAP®
sensors for measuring the ambient gas concentration in public buildings and offices. Since
people exhale carbon dioxide,
the CO2 concentration is a
good indicator of human presence in a room. Based on the
outputs the ventilation can be
controlled so that the air quality is good despite of the occu-
Receiver
pation varies strongly from
time to time. By proper ventilation on demand it is possible to
make essential energy saving.
In this application the stability
of the CO2 sensors is of vital
importance.
Examples of recent
applications
Air Force One, the plane of the
President of the United States
of America is, of course,
packed with sensitive electronic
systems. When the plane is on
the ground, the internal environment is carefully controlled
from an external air conditioning plant. Traditionally wired
sensors were trailed into the aircraft but these have now been
replaced with Hanwell humidity and temperature radio units.
The radio data is converted at
the receiver to 4–20 mA signals
which directly control the air
conditioning while the software continues its normal
monitoring functions. This approach has eliminated the continual problems experienced
with cabling.
Laboratories conducting environmental testing on a range
of products from food to pharmaceuticals require a flexible
method for adapting their monitoring systems as needs change.
The Hanwell system offers an
ideal solution, providing measurements that can meet the
high standards required by legislation. The same technology
can also be readily applied to
high technology manufacture
where quality control procedures insist on documented environmental data.
Comfort within office buildings or heat stress monitoring
in industrial environments is of
growing importance. Hanwell
have implemented a system
that automatically calculates
Control
interface
the wet bulb globe temperature
from the incoming radio data.
This gives an indication of the
heat stress on a body when
working in hot environments.
Modern energy efficient
buildings require independent
verification during commissioning to ensure that design specifications are being achieved. A
complete investigation might
require the short-term monitoring of temperature, humidity,
flow speeds, differential pressures and energy consumption
in a variety of locations. All of
these variables can be gathered
with minimal disruption to the
day-to-day operation of the
building.
If implemented properly,
radio telemetry can be of great
help to the instrumentation engineer. The list of applications
continues to grow and it seems
obvious that the popularity of
wireless sensor systems will increase dramatically in the coming years.
■
Networked PC
Sensors
Master PC
Repeater
Architect2
Controller
Modem connection
The flexibility of a typical radio telemetry system. The radio data is readily exported as analogue or digital data from the
base station, providing a highly flexible solution to a wide range of instrumentation and control problems.
154/2000 17
40234Ymi_Vaisala154
13.9.2000
08:51
Sivu 18
Vaisala’s new SPH10/20 static
pressure heads, ideal for outdoor
installations, were designed to
eliminate the effects of wind on
barometric pressure readings.
Vaisala has launched its new
SPH10/20 static pressure
heads designed to eliminate
the effects of wind on barometric pressure readings.
Effects caused by wind lead
to major errors in the barometric pressure measurement. According to WMO
recommendations, meteorological measurements must
account for these wind-induced effects.
SPH10/20 static pressure heads for
Reliable Barometric
Pressure Measurement
in All Wind Conditions
18 154/2000
Effects caused by buildings
Wind-induced effects are, perhaps, the main source of errors
in the barometric pressure measurement. Wind can be both a
direct and an indirect source of
error to the measurement.
Based on the patented principle, Vaisala’s new SPH10/20
static pressure heads are used to
minimize wind-induced errors.
Indirect influence means
changes in the pressure field
around an object, which can, for
instance, be a building. When
moving air encounters an object
it will cause an over pressure or
under pressure around it.
Neither the pressure inside a
building is immune to the wind
surrounding it. Potential sources
of error are due to pressure fluctuation inside the building
caused by wind, as well as by the
building’s possible air conditioning. Therefore, buildings should
not be used as ‘static pressure
heads’.
Direct influence means dynamic pressure changes to the
pressure intake of the instrument, caused by wind. A
barometer will not give a true
reading of the static pressure, if
it is affected by gusty wind.
Instead, its reading will fluctuate with the speed and direction
of the wind. This effect on the
pressure reading may be in the
order of several hectopascals.
These effects are also discussed in the WMO1 guide.
Minimizing a windinduced error
A preferable location for a
barometer would be an open
field without any obstacles
close to the barometer, which
Timo Ranta-aho, Tech. Lic.
Product Manager
Sensors Systems Division
Vaisala Helsinki
Finland
could disturb it. In strong and
gusty winds, the direct effects
can be cancelled out by using a
static pressure head to ‘filter
out’ the effect of dynamic pressure1. This type of head needs
to be designed carefully and
thoroughly.
In addition to having the
properties to minimize wind-induced error, several other factors
must also be taken into account
in the design of a pressure head.
It should preferably be small
with a hardy structure. It should
not contain channels that could
easily become blocked due to
rain or condensed water. All
channels should also remain
open in snowy and icy conditions. The structure should be
such that the head is easy to remove for service and cleaning.
All of these things have been
carefully considered in the design of the new Vaisala
SPH10/20 static pressure
heads. The structure of the
pressure heads consists of two
convex plates with openings to
the pressure channel at the axis
bar between the plates. The
structure is both vertically and
horizontally symmetrical, minimizing any effects due to the
wind direction. The lower plate
has openings on its base to
allow rain and condensed water
to flow out. The plates are
made of PC plastic and the bar
is made of sea aluminum, so as
to be corrosion resistant.
Two versatile models
There are two different models
available: the SPH10 is a basic
version and the SPH20, is a
heated version to ensure reliable operation in snowy and
icy conditions. The SPH heads
08:51
Sivu 19
were designed in co-operation
with the Laboratory of Aerodynamics at the Helsinki University of Technology (Finland),
and their wind tunnel was used
for testing the prototypes2.
A static pressure error is defined as the difference between
the measured static pressure
(through the pressure head)
and the actual static pressure.
Results can be presented as
pressure differences in pressure
units (hPa), but also as a pressure coefficient Cp, which is
useful in comparing the results
of different pressure heads, and
the measurement made at different air flow speeds.
The pressure coefficient Cp
is defined as:
Cp =
head is installed vertically, and
is generally relatively close to
the ground. Pressure heads usually tend to have some offset at
their pressure coefficient which
is usually negative, even at angles close to zero. This means
that part of the kinetic pressure
always remains as a pressure
measurement error in the
barometer output at all wind
speeds.
In SPH heads the geometry
sets the pressure coefficient between the plates as slightly positive. This is then adjusted to
zero by allowing the air to leak
to a lower pressure region.
Figure 2 shows that with SPH
heads at the angle of zero the
pressure coefficient is also close
to zero. Therefore the pressure
inside the pressure head closely
corresponds to the static pressure of a free air flow, regardless
of the wind speed.
Figure 1 also shows that with
SPH heads, the pressure error
is below 0.3 hPa at all angles
measured, (WMO recommendation for operational network
station barometers1) and below
this limit also at a flow of 20
m/s between angles of
–20…+20 °. The results are the
same, regardless of the horizontal direction of the air flow.
In many pressure heads this is
not the case due to some supporting arm or other structure
breaking the symmetry of the
head. Also, the pressure coeffi-
static pressure error
kinetic pressure
where
kinetic pressure = 0.5 x (density of the air) x (wind speed)2
For example, a pressure coefficient of 0.1 means that 10 %
of the kinetic pressure is still
left as a pressure error in the
pressure reading. Positive sign
means measuring too high, and
negative sign means measuring
too low a pressure through the
pressure head. As the static
pressure error is comparable to
the square of the wind speed, it
cannot be numerically compensated with a constant coefficient. Proper compensation
would require a compensation
coefficient for vertical and horizontal wind speed and direction, making numerical compensation a very complicated
task.
0.50
0.00
dP [hPa]
13.9.2000
10 m/s
20 m/s
30 m/s
-1.00
-1.50
-2.00
-40.00 -30.00 -20.00 -10.00
0.00 10.00 20.00 30.00 40.00
Angle of Air Flow (∞)
Figure 1. The pressure error (dP) measurements in a wind tunnel through
SPH heads as a function of the angle of the attacked airflow.
0.1
Measured pressure
difference and pressure
coefficient
Figures 1 and 2 show the measured pressure error and pressure coefficient of SPH heads
as a function of the angle of attack of the air flow. At an angle
of zero, the air flow comes directly from the side of the
head. In negative angles the air
flow hits the pressure head
from above and, in positive angles, from below.
The most important aspect
of the graphs is the angles close
to zero, because the pressure
-0.50
0
-0.1
10 m/s
20 m/s
30 m/s
CP
40234Ymi_Vaisala154
-0.2
-0.3
-0.4
-40.00 -30.00 -20.00 -10.00
0.00 10.00 20.00 30.00
40.00
Angle of Air Flow (∞)
Figure 2. The pressure coefficient (Cp) measurements in a wind tunnel through
SPH heads as a function of the angle of the attacked airflow.
154/2000 19
40234Ymi_Vaisala154
13.9.2000
cient in the vertical direction often behaves asymmetrically.
Ideal for outdoor
installations
The new pressure heads
SPH10 and SPH20 are easy
to install and easy to disassemble for service and
cleaning, even at the installation site. The plates are
made of ultra violet stabilized PC plastic to ensure
that the head maintains its
correct shape in all outdoor
conditions. The axis bar is
made of corrosion tolerant
sea aluminum. The warmed
SPH20 contains a thermostat to switch on the warming power at temperatures
where there might be a risk
of freezing. In addition to
minimizing the wind error,
SPH heads also protect
against rain and condensed
water, preventing capillary
condensation of a water
column in the pressure
channel, which would lead
to a pressure error.
The new Vaisala PTB210
Digital Barometer can be
directly installed on top of
the SPH heads. All other
barometers can be connected to the SPH head with
pressure tubing. SPH10
and SPH20 are the perfect
pair to complement all
Vaisala barometers, as they
ensure an accurate and reliable measurement in all
weather conditions.
■
08:53
Sivu 20
The PMI20 Digital Barometer Display is a
Perfect Partner for Vaisala’s
Digital Barometers
Vaisala’s new PMI20
Digital Barometer
Display is ideal for
manned weather stations and laboratories
and offers extensive
possibilities, as it confers additional properties to barometers.
The PMI20 is a barometric display which
can be connected directly to Vaisala’s
barometers.
T
here are several vital
requirements
for
barometers used in
meteorological installations. They include good
accuracy and long term stability, as well as stability over variations of ambient temperature.
Additionally, the barometer
should provide quick and easy
readings and should also,
preferably, indicate the trend of
pressure changes. The new
PMI20 barometric display is
ideal for these purposes.
Remote display with
control outputs
1] World Meteorological
Organization (WMO), Guide
to Meteorological Instruments
and Methods of Observation,
Sixth Edition, WMO-No. 8,
1996.
2] Palomäki P., Measurement
of Barometric pressure in the
Wind, Master’s Thesis (in
Finnish), Helsinki University
of Technology, 1999.
20 154/2000
The PMI20 Digital Display is
compatible with all of Vaisala’s
current barometers with a serial
output, as well as with the
PTU200 Pressure, Temperature
and Humidity Transmitter. The
PMI20 can be connected directly to a barometer. The display automatically identifies the type of
unit connected and sets the serial communication parameters.
The PMI20 is ideal for
manned weather stations and
laboratories. It has both an
RS232 and an RS485 connection to the barometer and to a
PC. As the RS485 allows for a
distance of up to one kilometer
between the barometer and the
display, the display may be used
as an in-house remote display for
a barometer installed outdoors at
the actual measuring site. The
display can easily be installed in
a standard panel cutout. Five
programmable, open collectortype control outputs allow the
display to also be used as a control unit and to control external
relays, for instance.
Various displayed values
The PMI20 digital barometer display is easy to use and the whole
operating menu can be controlled
with one knob. The PMI20 has a
large backlit display with 150 x 32pixel resolution. The measured
data can be outputted either in
metric or non-metric units and
the pressure unit can be selected
from eleven different alternatives.
Display settings can be secured by
setting a key code, which prevents
all changes to the unit and stops it
from being switched off without
the code.
The barometric display shows
the current pressure output of
the barometer, the calculated
three-hour pressure trend and
the WMO pressure tendency
The PMI20 Digital Barometer
Display is ideal for laboratories.
code simultaneously. Furthermore, a height-corrected pressure (HCP) can be calculated
and displayed for ±40 meters.
This enables the measured pressure to be reduced to a reference
altitude level – for example, the
surface of the runway at an airport or the sea surface level in
the case of a ship installation.
The display of the PTU200
transmitter shows all three measured parameters at the same
time; i.e. pressure, humidity and
temperature. The user can also
select the PMI20 special mode
as wished to show a dew point
(frost point) value.
The PMI20 has a battery secured memory which stores the
data measured over the last 24
hours. The user can view data on
the display as graphical trends or
download it to a PC.
■
40234Ymi_Vaisala154
13.9.2000
09:06
Sivu 21
PTB210 Series of Digital Barometers
Measuring for Extreme
Environments
Ideal for outdoor installations, Vaisala’s
new PTB210 series of
digital barometers can
monitor a wide range
of pressure and temperature. Due to their
compact structure, the
barometers can be integrated with weather
stations and other data
monitoring systems.
The rugged corrosionresistant housing,
combined with the
PTB210’s compact
size, facilitates easy installation and ensures
a long service lifetime.
V
aisala’s selection of
digital barometers has
been expanded by
the new PTB210 series. The configurable PTB220
digital barometer family gained
great market success after its introduction in 1995. The PTB220
provides several options, including a local display, and two or
three pressure sensors, incorporated for double or triple redundancy, for the most demanding
users.
RS232C (also available as TTL
level bidirectional output). The
optional RS 485 output also allows longer distances between
the barometer and the host system.
Accurate measurements
Wide pressure range
The PTB210 series of basic digital barometers with different
measuring ranges and output
options is the newest member
of Vaisala’s barometer product
family. All the barometers are
characterized and adjusted at
several temperature and pressure levels. The numerical compensations enable high accuracy over the full operating temperature range.
The barometers are available
in two basic configurations –
with serial or analog output.
The standard serial output is
Serial output models offer two
different measuring accuracy
classes for the range 500...1100
hPa. The higher accuracy class,
the class A barometer, is fineadjusted and calibrated against
a dead weight tester, while the
class B barometer is calibrated
against electronic working standards. A wider measuring range
50...1300 hPa is also available
with a serial output. Analog
output models can be supplied
with different pressure output
scalings between 500...1300 hPa
for either 0...5 V or 0...2.5 V.
The PTB210 series of digital barometers can be integrated with a weather station.
The housing of the PTB210
provides an IP65 (NEMA 4)
protection for the barometer
electronics against dust and
water. The ruggedness and corrosion resistivity of the housing
enables the PTB210 to be installed outdoors. Direct integration with Vaisala’s static pressure head facilitates accurate
and reliable measurements in
all wind conditions.
BAROCAP® sensor
technology
The PTB210 barometer incorporates the BAROCAP® silicon capacitive absolute pressure sensor
developed by Vaisala for professional meteorological instruments. The sensor is known for its
excellent hysteresis and repeatability characteristics and outstanding long-term stability.
■
154/2000 21
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Meteorological Service of Canada (MSC)
Digital Barometers at
Airport Locations
Marit Finne
Editor-in-Chief
Vaisala News
Vaisala Helsinki
Finland
Vaisala has been
awarded a contract by
the Meteorological
Service of Canada
(MSC). Vaisala supplies electronic station
barometers to replace
the mercury barometers currently used for
weather observations
throughout Canada.
The new digital
barometer is easy to
maintain, and is not
susceptible to exposure to temperature
extremes which may
vary from -20 °C to
+60 °C.
Electronic weather
station PTB220
barometers
The key persons involved with the contract at MSC from the left: Harry Lamb, Louise Smith, Dennis Wickiam,
Gerie Lynn Lavigne, Dave Dockendorff and Rodica Nitu (Rod Prior and Peter Bowman are missing).
The Meteorological Service of
Canada (formerly known as
the Atmospheric Environment
Service) is a Service under the
Department of Environment
located in Toronto, Ontario.
The Meteorological Service of
Canada (MSC) is the country’s
source for meteorological information. Vaisala was selected
to supply electronic station
PTB220 barometers for weather monitoring throughout
Canada.
Delivery of the barometers
began in the fall of 1999. The
project to replace all the mercury barometers will continue
through the year 2001. When
completed, this project will
eliminate the potential health
risk to observation personnel
and the potential contamination of the environment, as well
as helping to ensure the safety
of all passengers flying in and
out of Canada for years to
come.
For approximately seven
years Vaisala’s ceilometers and
upper air equipment have also
been used operationally in
MSC’s weather networks.
22 154/2000
MSC in a nut shell
The MSC traces its history to
the very beginnings of Confederation. For over 125 years,
the Canadian government has
provided its citizens with
weather and other atmospheric
environmental information and
predictions.
The mission of the MSC is to
anticipate and respond to the
evolving needs and expectations
of Canadians and their institutions for meteorological, hydrological and related information
and prediction services. The
Meteorological Service helps
Canadians adapt to their environment in ways which safeguard their health and safety,
optimize economic activity and
enhance environmental quality.
It is the goal of Environment
Canada to help make sustainable development a reality in
the country, and, by doing so,
make the country an example
to the world.
Need for digital
barometers
Vaisala’s PTB220 digital barometers will be integrated to AWOS
(Automated Weather Observing
Systems) and also to PCs used
by human weather observers to
generate and communicate various types of weather and climate
observations. These barometers
will be used at all hourly aviation and synoptic weather observing stations in Canada.
“The new and reliable digital
barometers are needed to eliminate human error in reading
mercury barometers, transcribing readings and calculating
various atmospheric pressure
values; specifically, altimeter
setting and mean sea level pressure. The use of digital barometers will allow us to automate
the barometric monitoring program in Canada,” MSC representatives say.
Evaluation process
and testing
The PTB220 was one of seven
barometers approved for operational use by the Meteorological
Service of Canada, and allowed
to take part in the bid. The
40234Ymi_Vaisala154
13.9.2000
PTB220 was the only digital
barometer which met the stringent requirements of the MSC.
“Laboratory tests were conducted over a period of more
than twelve months. They consisted of periodic calibration
checks (for evaluation of long
term stability), operating environment tests, storage and
shipping environment tests,
communications tests and
power tests. They were designed to simulate the extreme
conditions the barometers
would be subjected to if used
operationally at any of the stations in our observing networks,” MSC experts explain.
One reason why Vaisala’s
barometers were selected was a
cost/value ratio. In addition,
the unique PTB220 digital
barometer design incorporates
the three-cell redundancy required to give the necessary
level of confidence in the measurements. Multiple redundancies were required by NAV
CANADA, MSC’s main aviation data recipient/client.
Environmental and
safety issues
Mercury barometers pose a risk
to both the environment and
to personnel using them. The
mercury barometers in use at
observing stations are up to 70
years old. There is therefore an
increasing risk of both human
exposure and of environmental
contamination to leaking mercury.
The pressure measurements,
performed by observing personnel at airport locations are
used to compute altimeter settings, which are used by pilots
for aircraft landing and take-off
purposes. An incorrect altimeter setting could have disastrous consequences. It could
mean that the pilot believes the
aircraft which he/she is flying is
higher above the ground than
it actually is. When combined
with conditions of poor visibility and/or low cloud cover, this
could result in an airplane accident. For this reason, there can
be little or no tolerance for altimeter setting errors.
The use of digital barometers
should eliminate incorrect altimeter settings due to reading,
computational and transcrip-
09:06
Sivu 23
Vaisala’s PTB220 digital
barometers will be integrated to
AWOS (Automated Weather
Observing Systems) and also to PCs
used by human weather observers to
generate and communicate various
types of weather and climate
observations in Canada.
tion errors associated with mercury barometers and humans.
In addition, the multiple redundancy in the Vaisala barometers
combined with a special emergency back-up power supply
provides an added margin of
safety and reliability.
PTB220 barometers
with AWOS
MSC representatives explain:
“Other than our design processes, we have not had any experience to date. We are designing a
new digital pressure instrumentation for our AWOS which will
replace older dual pressure analogue technology. The multiplecell redundancy in the PTB220
version which we are using is expected to provide more reliability and an extra margin for safety than the current module.”
It is also planned to add
Mean Sea Level (MSL) pressure, pressure tendency and
density altitude reporting capability to the AWOS.
Benefits using digital
barometers
According to MSC, the benefits using PTB220 barometers
include long-term stability,
RS232 and RS485 compatibility and three independent transducers.
The back-up power supply will
extend the operation of the
barometer in the event of a power
failure. It also provides better immunity to electromagnetic interference and power fluctuations.
Unlike the mercury barometer
it is replacing, a PTB220 barometer is easier to maintain, and is
not particularly susceptible to ex-
One of Vaisala’s PTB220 digital barometers installed at London, Ontario,
Canada. Vaisala supplies electronic station barometers to replace the mercury
barometers currently used for weather observations throughout Canada.
posure to temperature extremes
(-20 °C to +60 °C) or damage
brought about by routine commercial shipping. When transporting mercury barometers,
they require special handling procedures, packaging and permits
to comply with Transportation of
Dangerous Goods regulations.
This is especially significant with
remote weather stations which
are accessible only by aircraft.
When using digital barometers, the need for periodic
cleaning and calibration of
mercury barometers is also
eliminated. This is very laborintensive and these services are
becoming very difficult and
costly to obtain.
Using PTB220 barometers,
MSC will benefit by more
timely and accurate atmospheric pressure and altimeter setting
values and a reduction in both
the time required for training
and performing atmospheric
observations.
■
Several key persons participated into
the contract process at MSC.
Dave Dockendorff, Manager, National Weather
and Climate Operations Division
Peter Bowman, Barometry Technical Authority
Rod Prior, Manager, Technical Operations
Harry Lamb, Electronics Systems Engineer
Rodica Nitu, Head Operational Engineering
Dennis Wickiam, Procurement Quality Assurance Auditor
Louise Smith, Chief, Electronics and Engineering Procurement, Public
Works and Government Services Canada
Gerie Lynn Lavigne, National Meteorological Systems’ Technologist
154/2000 23
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Biotechnologie–Kempe incorporates
Vaisala’s
Barometers
Used to Track
Leakage from
Nuclear
Enclosures
Vaisala’s PTB101C analogue barometers
are being used by the French Electricity
Company in their program to track
leakage from nuclear power plant enclosures.
T
hanks to fruitful co-operation between
Gianelli Mesures and Vaisala SA, some sixty
of Vaisala’s PTB101C analogue barometers
have been delivered to the French
Electricity Company (Electricité de France, or EDF).
The PTB101C has been installed in an instrument
cabinet with a 220V power supply by Gianelli Mesures,
a company located close to Valence, France.
The resulting unit is being used in EDF’s SEXTEN
program, designed to track leakage from nuclear power
plant enclosures.
The PTB100 series of analogue barometers is designed both for accurate barometric measurements at
room temperature and for general environmental pressure monitoring over a wide temperature range. The
excellent long-term stability of the barometers minimizes or even removes the need for field adjustment in
many applications.
The SEXTEN system measures the atmospheric
pressure inside nuclear enclosures with high precision
and stability. These enclosures are maintained at a
slightly higher pressure than the atmospheric pressure,
in the range 900 to 1100 hPa. The value of the outside
atmospheric pressure is also measured by the Vaisala
barometer and compared with the inside pressure. The
allowed rate of leakage from each enclosure, proportional to the difference between the inside and outside
pressures, is calculated from these two sources of information.
All of the French nuclear power plants in the 900,
1300 and 1450 megawatt range have been equipped
with this system.
■
24 154/2000
Dissolved CO2
Measurements
F
or over 15 years Biotechnologie Kempe
GmbH has been situated in Berlin and
has been active mainly in the
field of measuring and regulating technology for biotechnology and environmental protection at the international level,
where our export share is about
90 per cent. Our workshops
produce measuring technology,
electrical components, scientific instruments and machines,
and, in order to control fermentation procedures, we have
a self-owned programming
technology department at our
disposal.
A major field of achievement
for Biotechnologie Kempe
GmbH is our development of
measuring probes (EU and US
patent), as well as systems for
the registration of measurements. This results in the opportunity to develop customeroriented, personalized automating concepts, thus achieving
highly economical production.
Biotechnologie Kempe’s new
probe incorporates Vaisala’s
GMM220 series carbon dioxide
sensor. The GMM220 series
sensors are based in CARBOCAP® technology, enabling
trouble-free control of CO2 levels in demanding environments.
Carbon dioxide in
biotechnology
Carbon dioxide is a product of
the respiratory and fermentative metabolism of micro-organisms. During fermentation
the carbon dioxide emission
correlates with the biomass
concentration and substrate
consumption.
Depending on the concentration, carbon dioxide may influence the growth and metabo-
lism of micro- organisms. For example, a high concentration of
carbon dioxide leads to a delay
in budding of Saccaramyces
cerevisiae, so the reproduction
of yeast is influenced negatively.
Further, the negative effect
of a very low carbon dioxide
concentration on the metabolism during aerobic substratelimited yeast fermentation is
well known and results in a
yield loss. Also, the formation
of products and by-products in
the fermentation processes frequently depends on the content of carbon dioxide in the
medium.
On-line monitoring of
dissolved carbon dioxide
Continuous detection of carbon
dioxide by the presented measuring system is realized by the
combination of a silicone tubing
probe and a Vaisala GMM220
carbon dioxide probe. Vaisala’s
GMM220 series modules incorporate enhanced CARBOCAP®
tehcnology. Many advanced features enable trouble-free control
of carbon dioxide levels in extreme environments.
The CO2 measurement is carried out as follows:
• directly in the fermentation
broth, where carbon dioxide
is formed and where the
micro-organisms are affected
by CO2.
• in the gas stream
• both above and below the
carbon dioxide saturation
achieved under atmospheric
pressure
• without any preparation of
the exit gas
• with high stability
• with a short response time
40234Ymi_Vaisala154
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Vaisala’s GMM220 series sensor
Biotechnologie Kempe’s new probe is equipped
with Vaisala’s modular carbon dioxide
GMM220 series sensor. The GMM220 series
CO2 modules incorporate the CARBOCAP®
technology. The sensor’s operation is based on
the NDIR Single-Beam Dual-Wavelength principle. Its main advantages are long-term stability
and a long life.
Yeast cells
Vaisala’s CO2 probe GMM220
Eberhard Kempe, (Dipl.Eng.)
Managing Director
Biotechnologie-Kempe GmbH
Berlin, Germany
Biotechnologie Kempe’s silicone tubing
probe for dissolved carbon dioxide.
Double membrane
(Silicone + Teflon)
Silicon tubing probe
Protecting tube
The silicone tubing probe was
developed by Biotechnologie
Kempe GmbH (EU and US
patent) and is steam sterilizable.
The probe, which is inserted
into the broth, consists of a silicone coated channel through
which is passed a carrier gas.
Carbon dioxide permeates
through the silicone membrane
and is carried to the CO2 sensor.
The measuring principle of
the system is based on the linear
relationship between the partial
pressure of carbon dioxide inside
the broth and the amount of carbon dioxide permeating through
the membrane. The concentration of CO2 in the carrier gas is
far from the equilibrium concentration, so permeation back into
the broth is negligible.
The carrier gas control and
the signal converter are located
inside a separate box.
Signal processing
The gas is measured by absorption of infrared radiation inside
the CO2 sensor located in the
housing of the ST probe. The
infrared radiation emitted by a
lamp passes through a filter
working at the selective wavelength which is characteristic
for absorption by carbon dioxide. If there is carbon dioxide
inside the measuring cell, the
intensity of light decreases in
154/2000 25
13.9.2000
relation to the actual CO2 concentration.
The ST probe described here
is equipped with Vaisala’s modular CO2 sensor. The CARBOCAP® sensor is silicone based
and operates on the NDIR
Single-Beam Dual-Wavelength
principle. Based on this new
measuring principle, its main
advantages are long-term stability and a long life – the main
reasons why we chose Vaisala’s
product for our carbon dioxide
application.
The output of the sensor
(Signal Converter Module) is 0
(4) – 20mA and a serial interface RS-232 is available.
Additional signal processing
is realized by connecting the
CO2 probe to a measuring
computer FMC-MINI LCD.
This is a modification of an existing measuring computer
which is successfully used in
biotechnology to detect volatile
organic compounds. The system for measuring carbon dioxide is a new development by
Biotechnologie Kempe.
The carbon dioxide concentration in the carrier gas is
shown as % Vol. after processing by the computer.
Based on the detected concentration in the carrier gas, the
computer calculates the partial
pressure of CO2 in the fermentation broth. The next step is
the calculation of the dissolved
CO2 by means of the additionally measured temperature. The
influence of other compounds
on the solubility of CO2 can be
compensated for with the computer program. The measuring
computer realizes the collection of values, processing, calibrations and graphs.
Measuring range
Several CO2 probes are offered
for measuring the dissolved carbon dioxide concentration by
the described principle, in accordance with the measuring
range.
The measuring range is fixed
by the carrier gas flow rate,
which, in turn, depends on the
nozzle being used. Depending
on the chosen nozzle, a measuring range of 0–50 % or 0–100
% of saturation can be realized.
These probes are offered for
using during no-pressure fer-
26 154/2000
09:07
Sivu 26
mentation; a probe which covers a range of 0–500 % saturation, for use during pressurized
fermentations, is also available.
Carbon dioxide
applications
Carbon dioxide is a product of
the cellular metabolism of
micro-organisms used in biotechnology. During fermentation the carbon dioxide content is the result of carbon
dioxide formation by the
micro-organisms and its transport by aeration. By means of
the CO2 probe it is possible:
The Vaisala GMM220 series CO2 measurement
modules based on CARBOCAP® technology.
GMM220 Series
Carbon Dioxide
Measurement Module
• to detect the carbon dioxide
concentrations which inhibit the metabolism and
growth of micro-organisms,
so the user is able to start
compensating measures –
for example, aeration.
• to obtain information about
the growth and activity of
micro-organisms during fermentation.
T
he Vaisala GMM220 series CO2 measurement modules
incorporate the enhanced CARBOCAP® technology.
The transmitters have been optimized for integration
into equipment for greenhouse control, incubators, fermentors, safety alarms and integrated systems.
Many advanced features enable trouble-free control of CO2 levels, even in demanding applications and harsh environments.
The GMM220 series transmitters provide both time and temperature stability thanks to the CARBOCAP® sensor’s constant reference measurement.
Fully interchangeable probes make the GMM220 series transmitters very versatile. The probes do not only simplify calibration
and field service, but they also make it easy to alter the measurement range. Different power supply voltages and output options as
well as different probe attachments are also available.
■
• to realize the control of
anaerobic fermentations.
Carbon dioxide also plays an
important role as a quality parameter in the beverage and
brewery industry and can be
detected by the measuring system in order to ensure the quality of the final product.
■
Typical calibration curve for C02 probe
20
18
16
Output of Probe (mA)
40234Ymi_Vaisala154
14
12
10
8
6
4
2
0
0
1
2
3
4
5
Dissolved carbon dioxide conc. in the liquid (g/l)
Calibration curve (related to a beverage industry application).
6
7
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Sivu 27
Measuring
Carbon Dioxide
in the Soft Drinks
Industry
Carbon dioxide is used to carbonate the beverages in the production of soft drinks. In the
United States, OSHA requires that the CO2
level remains at, or below, 5,000 ppm in the atmosphere of any filler room area. Big Springs
Inc. is a major soft drink manufacturer and a
large local Coca-Cola franchise distributor located in Huntsville, Alabama. The company has
successfully used Vaisala’s CARBOCAP transmitters for more than a year in their bottling
plant.
Marit Finne
Editor-in-Chief
Vaisala News
Vaisala Helsinki
Finland
B
ig Springs Inc. is a
major soft drink
manufacturer and a
large local CocaCola franchise distributor located in Huntsville, Alabama,
USA. John M. Wilkinson, the
Administrative Manager, who
has worked for 28 years in the
company, is in charge of
Facility Maintenance. He also
oversees the Human Resources
Department.
There is a growing need for reliable measurement of carbon
dioxide in bottling plant environments. The lack of reliable
and inexpensive instruments has
made CO2 measurement difficult and costly. Cooperation between Big Springs Inc. and
Vaisala began when Wilkinson
found Vaisala’s CO2 products
through the Internet.
Safe levels of CO2 in the
workplace
Carbon dioxide is used to carbonate the beverages in the
production of soft drinks.
While the containers are being
filled during the bottling process,
large volumes of carbon dioxide are emitted from the fillers
into the filler room atmosphere.
As high concentrations of
CO2 are clearly hazardous,
most countries, including the
USA, have set workplace exposure limits. In the United States,
the exposure limit is 5,000 parts
per million (ppm). Occupations
where carbon dioxide can rise to
dangerous levels include brewing and carbonated drink industries.
In the United States, OSHA
(Occupational Safety & Health
154/2000 27
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09:08
Sivu 28
The carbon dioxide exhaust fans in the filler room are capable of 15 air
changes per hour at Springs Inc., which is a major soft drink manufacturer
and a large local Coca-Cola franchise distributor located in Huntsville,
Alabama.
Administration, U.S. Department of Labor) requires the average exposure limit of CO2 in
weight to remain at, or below,
5,000 ppm during an eight hour
working shift. Mr. Wilkinson explains: “We purchased Vaisala’s
CARBOCAP transmitters to
monitor the levels of CO2 in
the filler room. The information from the transmitters is
transmitted to the ABB Chart
Recorders. The chart recorders
monitor and log these levels.
When they sense levels over
4,900 ppm, an exhaust fan system is activated to remove the
CO2 from the filler room. The
fans turn off once the level returns to 1,000 ppm.”
Cooperation began
through the Internet
According to Mr. Wilkinson,
Big Springs Inc. has worked together with Vaisala for more
than a year. “Research on the
Internet led me to Vaisala’s
Boston Office. After studying
the company, I discovered that
Vaisala has a long history of
quality products and reliable
services. Not only that, but the
transmitters did not require calibration either. The products of
most other companies require
constant calibration. Another
reason for choosing Vaisala’s
products was Mr. Richard
Kershaw, from the Boston
28 154/2000
Office. He and the technical
staff worked with me to create
the system that we are currently using.”
Benefits of reliable CO2
measurement
Mr. Wilkinson says that they
have generally been satisfied
with the CO2 transmitters. “The
fact that we don’t have to calibrate the CARBOCAP transmitters saves time. The system
simply runs by itself and requires little or no maintenance.
I do not believe that there is another company that could
match the efficiency and reliability of Vaisala’s products, sales
and services.”
■
The GMT220 series transmitters are designed to measure
CO2 in demanding environments.
GMT220 Series
Industrial Carbon
Dioxide
Transmitter
T
he Vaisala GMT220 is the first range of CARBOCAP® transmitters available for a wide range of
CO2 applications including greenhouses, fruit storage, safety alarms and demand-controlled ventilation in mushroom farms, livestock husbandry and car park
garages. The GMT220 series transmitters are designed to measure CO2 in harsh and humid environments. The housing is
dust and water proof to IP65/NEMA4, and the materials have
been chosen to be particularly resistant to corrosion.
The transmitter is easy to install and use. The GMT220 series transmitters have a modular structure, which includes a
separate mounting plate to facilitate installation.
The probes of the transmitter make field maintenance
straightforward, because they are fully interchangeable. The
probes can either be replaced by newly calibrated probes or
separate ones that can be used as reference probes for checking calibration. This minimizes the downtime and eliminates
the need for expensive calibration equipment.
■
40234Ymi_Vaisala154
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09:09
Sivu 29
Outdoor plant growth experiments in
Elevated CO2 Atmospheres
A silent giant, Mount Iwate,
guards the peaceful surroundings of
the Tohoku Research Center on the
northern mainland of Japan.
The Forestry and Forest Products Research Institute studies plant
growth in elevated carbon dioxide environments in Japan. At the
end of 1999, Dr. Mori started a four-year project to study the effects
of carbon dioxide and soil nutrient content on young trees. Vaisala
is involved in this project, providing essential carbon dioxide
measurement instruments for the outdoor growth chambers.
From left, Mr. Gaku Hitsuma, Mr. Tatsushiro Ueda and
Dr. Shigita Mori on location at the open top chambers.
Shigeta Mori, Ph.D.
Tohoku Research Center
Forestry and Forest Products
Research Institute
Tatsushiro Ueda
Environmental Equipment
Section
Hokkaido Dalton Co., Ltd.
Juhana Häkkänen, M.Sc. (Tech.)
Business and Process
Development Manager
Vaisala Tokyo
Kennichi Ishimoto, L.L.B.
Technical Consultant
Vaisala Tokyo
Japan
A
now silent giant,
Mount Iwate, guards
the peaceful surroundings of the
Tohoku Research Center on
the northern mainland of
Japan. The volcano’s fiery prehistoric past, is a strong reminder of how our environment is undergoing constant
change. Since the birth of
‘Iwate san’, mankind has
emerged and evolved into an
increasingly influential component of our planet’s ecosystem.
For the first time in Earth’s history, it seems that a single
species is capable of altering
the entire climate system.
154/2000 29
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09:10
Sivu 30
Vaisala CO2 instruments
in forest study
The consequences that global
warming has on nature are still
largely unknown. Japan is at
the forefront of a global effort
to study the phenomenon, and
to try to minimize its impact.
Proof of this is the United
Nations’ Kyoto Protocol aimed
at a worldwide reduction of carbon dioxide and other green
house gas emissions.
The Japanese high authority
in forestry issues, the Forestry
and Forest Products Research
Institute (FFPRI), has played
an active role in assessing the
effects of rising temperature
and carbon dioxide (CO2) concentration. The FFPRI, with its
five research centers around
Japan, is currently carrying out
numerous research projects on
the subject. One of these involves studying plant growth in
elevated carbon dioxide environments. Vaisala is also involved in this project, providing essential CO2 measurement instruments for the outdoor growth chambers.
Tohoku Research Center
The FFPRI Tohoku Research
Center in Morioka is responsible for forest preservation and
research in Tohoku, covering
an area of almost 67,000 km2,
over two thirds of which is forest. The majority of the forests
are owned either by national or
local government. The research
center is creating a long-term
30 154/2000
Vaisala’s CO2 measurement instruments are
used in the outdoor growth chambers.
plan to ensure the well being of
the Tohoku forests in the future. It is possible that the effects of global warming can already be seen in various trees in
the forests of Tohoku. It seems
that the slight climate change
and rising concentration of carbon dioxide in the atmosphere
are allowing some pests to
spread more easily from the
south. The complicated migration patterns of forest pests are
one example of the new challenges that the research center
is facing.
Dr. Shigeta Mori has been
conducting research projects
for Tohoku Research Center
over the last two years. Before
Morioka, he spent four years at
the FFPRI Hokkaido Research
Center. He has a doctorate in
agriculture from the Nagoya
University Graduate School of
Agriculture and Forestry, and
has participated in numerous
research projects in different
parts of Japan. “Japan is a
unique country for a forest researcher,” explains Dr. Mori.
“Although it is a moderately
small country in terms of surface area, it stretches right
through the forest zone of the
Northern Hemisphere. Japan’s
southernmost islands and the
island of Kyushu are in a subtropical forest zone and the island of Hokkaido in the north
is in a cool-temperate forest
zone. As most areas of Japan
also have high mountains, the
variety of domestic types of forest is remarkable.”
Dr. Mori has led innovative
research projects not only in
Japan, but also in Siberia and
Indonesia. Few researchers
have had the opportunity to
experience such a wide range of
different forests, from equatorial tropical rain forests to huge
larch forests in the permafrost
of northern Russia.
Open top growth
chambers
At the end of last year Dr. Mori
started a four-year project to
study the effects of carbon dioxide and soil nutrients on young
trees. The project is supported
by a grant for the ‘Development
of detailed methods to evaluate
CO2 budgets in forest and
ocean ecosystems’, funded by
the Ministry of Agriculture,
Forestry and Fisheries in Japan.
If all goes well, Dr. Mori’s study
will eventually provide new information on the physiological
changes that plants undergo in
modified atmospheres. These
changes, e.g. different allocation
of chemicals within the plant,
could alter their resistance to the
pests mentioned above. It is essential to comprehend these
basic mechanisms in order to
understand the nature of plant
behavior in changing environments.
Since his projects in Siberia,
one of Dr. Mori’s partners has
been Hokkaido Dalton Co.
Ltd., a company specializing in
designing and manufacturing
professional equipment for research and experiments. Once
again, the expertise of Mr.
Tatsushiro Ueda from Hokkaido
Dalton was needed. Under the
guidance of Dr. Mori, sixteen
open top chambers (OTCs) in
total were designed and built on
the test grounds of the Tohoku
Research Center. The growth of
identically cloned cuttings of a
hybrid larch, a cross between
Japanese larch (Larix kaempferi)
and Dahurian larch (Larix
gmelinii), is monitored in these
chambers. The cuttings are
grown in four different environments: two with different atmospheric carbon dioxide levels and
two with different levels of soil
nutrients.
40234Ymi_Vaisala154
13.9.2000
09:10
Sivu 31
CO2: 360 ppm
low nutrients oil
CO2: 720 ppm
low nutrients oil
CO2: 360 ppm
high nutrients oil
CO2: 720 ppm
high nutrients oil
Figure 1: Four different growth environments are monitored.
After four years of growth
monitoring, the small trees will
be cut down and analyzed
thoroughly. In the growth
chambers, the plants are subject to outside temperature, humidity and rainfall. As an OTC
is closed in at the sides by
transparent plastic film, the air
that circulates around the
plants can be enriched with a
particular gas; in this case, carbon dioxide.
CARBOCAP® technology
for research use
To provide sufficiently reliable
data for a scientific project, sets
of four chambers all have the
same gas and soil composition.
Therefore, a total of sixteen
chambers was needed (Figure
1). The carbon dioxide concentration of each chamber is measured by individual Vaisala CO2
transmitters fitted in the chambers. Half of the chambers are
maintained at near atmospheric background concentration of
360 ppmvol and the rest at an
enriched environment of double background concentration,
720 ppmvol. The Hokkaido
Dalton control system and carbon dioxide bottles needed for
the enrichment are in a small
hut adjacent to the chambers.
The control system not only
precisely regulates the CO2 levels of the OTCs, but is also
equipped with data logging for
all important parameters.
Dr. Mori and Mr. Ueda were
previously familiar with Vaisala
instruments, as the FFPRI has
used them in several projects.
“Everyone involved in producing important environmental
measurements knows Vaisala,”
says Dr. Mori. Up until now,
Vaisala products have been
used by the institute to measure more traditional weather
parameters, including barometric pressure, humidity and temperature. In these new chambers, Vaisala’s innovative CARBOCAP® technology has been
harnessed for research uses.
This was only natural because
dependability and good longterm stability were the decisive
factors in the choice of the
CO2 transmitters.
Juhana Häkkänen
Continuing the search
for clues
It will be several years before
final conclusions will have
been made in Dr. Mori’s and
Mr. Ueda’s current project. In
the meantime however, the
Forestry and Forest Products
Research Institute will actively
search for answers. One of their
ambitious targets is to calculate
the carbon dioxide balance of
the entire Japanese forest system, by 2002.
Just as there are many factors
involved in causing global
warming, many answers are
also required to solve the puzzle. The joint efforts of the
FFPRI research centers are
making a difference in this crucial issue, and Vaisala is pleased
to offer any assist it can.
■
154/2000 31
40234Ymi_Vaisala154
13.9.2000
09:10
Sivu 32
Service and Calibration
at Standard Prices
The Vaisala After Sales Service for humidity,
barometric pressure and carbon dioxide products in Europe has increased its range of services. In addition to service and repair facilities,
our European Service Center offers factory calibration facilities to customers in Europe, Israel
and South Africa. The first parameter in this factory calibration service is relative humidity.
Päivi T. Laitinen,
B.Sc. (Env. Eng.)
Technical Writer
Sensor Systems Division
Vaisala Helsinki
Finland
Vaisala’s European Service Center
provides full service for its
customers. The after sales facilities
include calibration, service, spare
parts and transportation at
standard prices. The European
Service Center is located in Helsinki.
Calibration – an integral
part of maintenance
T
he Vaisala After Sales
Center in Europe
has changed its service pricing principles for humidity, barometric
pressure and carbon dioxide
products. As of April 3, 2000,
After Sales has used standard
pricing for repairing and calibrating Vaisala products. The
standard price for repairs and
calibrations includes transportation, service and calibration work and spare parts. In
Europe, the service is based in
the European Service Center in
Helsinki.
Since the physical and electrical properties of materials do
not remain constant, measurement instruments have to be
calibrated regularly for them to
maintain their accuracy. As a
part of After Sales Services in
Europe, Vaisala offers factory
calibration services. The first
parameter included in this calibration system is humidity.
“Humidity was chosen because of Vaisala’s particular expertise in the area,” says Mr.
Jori Valli, European Service
Manager. It is recommended
that humidity instruments be
calibrated on a regular basis.
“The calibration interval depends on the instrument, the
required accuracy and the measurement environment. The average calibration interval for
humidity products is normally
one year.”
Calibrations can be divided
into two categories: one-point
and multi-point calibrations.
The user can perform a onepoint calibration, and it is used
for frequent spot checking of
instruments on the field. This
field calibration can usually be
carried out without disconnecting the instrument, by using a
recently calibrated portable instrument, such as the Vaisala
HMI41 digital indicator, as a
reference. One-point calibrations can also identify instruments that need further adjustment.
VAISALA NEWS
4
▼
32
5
13.9.2000
09:11
Sivu 33
Multi-point calibrations are
best suited to regular calibrations in stable indoor conditions. The Vaisala HMK15 is a
multi-point humidity calibrator based on saturated salt
baths. When a multi-point calibration is performed, the instrument is checked at two or
more stable points of relative
humidity; for instance, up to
three humidities can be generated using the HMK15 calibrator. This naturally means higher accuracy over the whole
measurement range than with
one-point calibration.
Trained personnel consisting of
seven service technicians and
one test engineer perform factory calibrations in a controlled
environment. To verify the results, two calibration certificates
are issued per calibrated instrument. The first calibration certificate is produced before the
adjustment and the second after
the adjustment. This two-certificate system makes it possible,
amongst other things, to continually monitor the operation
level of the calibrated product.
Reliable and
professional calibrations
Vaisala’s factory calibration is
carried out using a batch calibration system based on a computer controlled humidity generator, with software. According
to Mr. Valli, the advantages of
batch calibration methods are
capacity and speed: “The batch
calibration system allows for
higher accuracy than salt calibration. The whole calibration
process is also rapid due to the
short stabilizing time of the calibrator.” The batch calibrator
also provides traceability directly to the National Physical
Laboratory (NPL) in the United
Kingdom. In some quality systems traceable calibration certificates are a requirement.
▼
For a customer, the easiest way
of handling multi-point calibrations is to send the instrument
to Vaisala. Our factory calibration is carried out using five calibration points. This makes calibration more reliable. As Mr.
Valli notes: “Sensors seldom behave in a purely linear way. Five
calibration points and very accurate references give us more
accurate data from the middle
of the measurement area.”
The Vaisala After Sales Service
for humidity, barometric pressure and carbon dioxide is led by
After Sales Manager Jaakko
Laurikainen and European
Service Manager Jori Valli.
Traceable to the NPL
6
A product calibrated using
the Vaisala calibration service
will receive a calibration sticker
showing the date when the device was calibrated. In the future, a customer can also take
part in the Vaisala calibration
reminder program. The participants of this program will receive a letter, on a yearly basis,
reminding them of the recommended calibration and requesting them to send the instrument to Vaisala to be calibrated. This service will be
launched at the end of the year
2000.
■
European Service Summary
The standard price for calibration includes:
• free transportation by courier
• calibration work and certificate
• wearing parts (e.g. filters)
The standard price for repair and calibration includes:
• transportation by courier
• service work and spare parts (e.g. sensors)
• calibration work and certificate.
The standard price does not include probes and probe cables.
▼
40234Ymi_Vaisala154
7
154/2000 33
40234Ymi_Vaisala154
13.9.2000
Mike Johnson
Laboratory Manager
and
Kim Vacca
Customer Service Manager
Vaisala Boston
USA
At the beginning of
2000 the Vaisala
Boston Service Center
conducted a survey
entailing a variety of
questions covering the
entire after-sales
process. The survey
showed that 98 % of
customers were either
satisfied or highly satisfied with Vaisala’s
products, with the majority being highly satisfied. The survey also
showed that 96 % of
those who responded
expressed their satisfaction with Vaisala’s
service.
09:12
Sivu 34
Boston Service Center’s number one goal
Meeting the Demands
of the Customer
O
ver the years, the industry’s focus on
customer service and
customer support
has intensified to a degree that
companies have begun to distinguish themselves by this particular aspect. Companies have
begun to understand the need
for offering more than just a
quality product. The after-sales
process is now just as important as the sales process. When
it comes to making a business
grow, keeping existing customers satisfied is just as important as finding new customers.
There are several facets to
customer service and customer
support. First and foremost are
quick and accurate answers.
Whether there are technical inquiries, status of order requests,
or just general questions, answers must be prompt and to
the point. In almost all cases,
the question or inquiry needs
to be answered immediately,
and we make a point of providing our customers with answers
on the same day, even if we
simply acknowledge the question and inform the customer
that we are working on it.
Customer service
orientation
The Vaisala SSD Service Center
in Boston has worked extremely hard over the years to offer
customers better service than
that provided by all of our competitors. Each member of the
team understands the need to
reflect this attitude at all times
and work in accordance with
the guidelines that have been
set out and which put us above
the industry standard.
34 154/2000
Calibration of humidity and
temperature equipment can be
carried out anywhere. It is up
to the customer whether to return the unit to Vaisala for service. With competition for this
business increasing, the need to
continually improving one’s
capabilities is essential. Being
able to support the product
that has been sold is a crucial
role for a Service Center.
Vaisala has taken the necessary
steps to ensure that accurate
testing and support for products can be carried out at each
Service Center. The Boston
Service Center provides calibration traceable to the
National Institute of Standards
and Technology (NIST).
We also continue to support
and service our older-generation products.
Improved after-sales
support
Over the last several years, The
Vaisala SSD Service Center in
Boston has continually improved upon all aspects of
after-sales support. The success
of this improvement can be
measured in many ways, and
most obviously from a survey
of actual customer responses.
At the beginning of 2000 the
Vaisala Boston Service Center
conducted a survey entailing a
variety of questions covering
the entire after-sales process. 61
out of the 150 surveys were
completed and returned. The
results were extremely positive
and showed that the direction
we are taking has proved to be
correct.
The survey showed that 98 %
of customers were either satisfied or highly satisfied with
Vaisala products, with the majority being highly satisfied. The
survey also showed that 96 %
of those who responded expressed their satisfaction with
Vaisala’s Service, and 46 % of
these were highly satisfied. The
survey allowed customers to
voice their comments, and
Laboratory Capabilities
200
150
100
50
Low Range
High range
0
-50
-100
RH
Traceability
T °C
Traceability
Td °C
Traceability
T °C
Expanded
Testing
The SSD Calibration Laboratory includes equipment that will allow for
testing at various temperatures, dewpoints and humidities.
13.9.2000
09:12
Sivu 35
P H O T O S B Y K I M VA C C A , VA I S A L A B O S T O N .
40234Ymi_Vaisala154
From the left, Kim Vacca (Customer Service Manager) and
Lori Summerlin (Customer Service Representative from the
Customer Service Department in Boston. They handle all
customer inquiries on service, repair, expediting and tracing
orders, and any problems with orders or shipments.
most were very positive about
the sales staff and customer service personnel. Comment such
as trust, confidence and reliability appeared several times.
Flexible internet access
Mike Johnson, Laboratory Manager
Rejane Smith, Senior Service Technician
In today’s market, end-users are
presented with several choices
when they need calibration or
service. Providing something
that is better than the rest can
make the difference. This does
not mean simply talking about
service and support, but following through the actual
process. It is even easier to access us via our web-site
(www.vaisala.com/inc/ssdcat)
for technical support, order inquiries or field returns. The
standard turn-around time is,
on average, between two to
three days for all repairs performed in the Boston Office.
We also offer an express
turnaround, which allows serviced products to be shipped
back within two days. Our
Calibration Reminder Program
is made up of over 3,900 pieces
of equipment. As part of the
program a reminder is sent out
a month before the calibration
is due. This allows customers to
keep track of their equipment
to ensure that it is calibrated at
regular intervals.
Developing customer
training
The staff of the SSD Calibration/Service Laboratory in the
group picture. From the left, (seated) Gary Francisque, Ed
Mehu and Chang Pyun, (back row), Paul Joyce, Linda Hall,
Patsy Wheeler, Rejane Smith and Mike Johnson.
two or three day event in designated regions of the United
States that will combine a detailed presentation with a
hands-on working session.
The automotive industry has
toughened its requirements on
the quality system of its vendors. This industry has adopted
QS 9000, which means that all
suppliers must be ISO Guide
25 accredited (soon to become
ISO Guide 17025). The SSD
Calibration Laboratory is looking to attain accreditation
through third party assessment.
The implementation and documentation of accreditation will
further improve the calibration
process, which will be of great
benefit to most customers. This
is yet another way in which
Vaisala is committed to meeting all of the demands of a
changing industry.
The Vaisala Service Center
has evolved into a highly successful operation. Meeting the
demands of the customer is the
number one goal. We have purchased equipment that will
allow for testing at various temperatures, dewpoints and humidities. We are able to simulate most processes on the field
so that those products can be
tested as close to the conditions of their environment as
possible. We are committed to
serving our customers with the
best turn-around time without
reducing quality.
■
To further improve the aftersales process the Vaisala SSD
Service Center is working on
developing a training course to
educate customers on products, theory, calibration and
measurements. The training
course will take the form of a
154/2000 35
40234Ymi_Vaisala154
4.9.2000
17:02
Sivu 36
www.vaisala.com
Europe
North America
VAISALA Oyj
P.O. Box 26, FIN-00421 Helsinki
FINLAND
Phone int.: +358 9 894 91
Telefax: +358 9 894 9227
http://www.vaisala.com
VAISALA Inc.
100 Commerce Way
Woburn, MA 01801-1068
USA
Phone int.: +1 781 933 4500
Telefax: +1 781 933 8029
Vaisala Malmö
Drottninggatan 1 D
S - 212 11 Malmö
SWEDEN
Phone int.: +46 40 298 991
Telefax: +46 40 298 992
Phone from Sweden:
0200 848 848
Telefax from Sweden:
0200 849 849
Vaisala Inc.
Boulder Operations
8401 Base Line Road
Boulder, CO 80303-4715
USA
Phone int.: +1 303 499 1701
Telefax: +1 303 499 1767
VAISALA Ltd
Newmarket Office
Suffolk House
Fordham Road
Newmarket
Suffolk CB8 7AA
UNITED KINGDOM
Phone int.: +44 1638 674 400
Telefax: +44 1638 674 411
VAISALA Ltd
Birmingham Operations
Vaisala House
349 Bristol Road
Birmingham B5 7SW
UNITED KINGDOM
Phone int.: +44 121 683 1200
Telefax: +44 121 683 1299
VAISALA SA
2, rue Stéphenson (escalier 2bis)
F-78284 Saint-Quentin-EnYvelines Cedex
FRANCE
Phone int.: +33 1 3057 2728
Telefax: +33 1 3096 0858
VAISALA Dimensions SA
7, Europarc Ste-Victoire
F-13590 Meyreuil
FRANCE
Phone int.: +33 4 4212 6464
Telefax: +33 4 4212 6474
VAISALA KK
42 Kagurazaka 6-Chome
Shinjuku-Ku
Tokyo 162-0825
JAPAN
Phone int.: +81 3 3266 9611
Telefax: +81 3 3266 9610
VAISALA KK
Osaka Branch
1-12-15, Higashimikuni
Yodogawa-Ku, Osaka 532-0002
JAPAN
Phone int.: +81 6 6391 2441
Telefax: +81 6 6391 2442
VAISALA Pty Ltd
3 Guest Street
Hawthorn, VIC 3122
AUSTRALIA
Phone int.: +61 3 9818 4200
Telefax: +61 3 9818 4522
A.C.N. 006 500 616
VAISALA Beijing
Representative Office
Wangfujing Grand Hotel
Room 518-520
57, Wangfujing Street
Beijing 100006
PEOPLE’S REPUBLIC
OF CHINA
Phone int.: +86 10 6522 4050
Telefax: +86 10 6522 4051
VAISALA Regional Office
Malaysia
2nd Fl. Wisma Chinese Chamber
258 Jalan Ampang
50450 Kuala Lumpur
MALAYSIA
Phone int.: +60 3 457 1376
Telefax: +60 3 459 1176
/Offset-kopio Oy 2000
Vaisala GmbH
Bonn Office
Adenauerallee 46 a
D-53110 Bonn
GERMANY
Phone int.: +49 228 912 5110
Telefax: +49 228 912 5111
Asia and Pacific
ISO 9002
VAISALA GmbH
Stuttgart Branch
Zweigniederlassung
Pestalozzi Str. 8
D-70563 Stuttgart
GERMANY
Phone int.: +49 711 734 057
Telefax: +49 711 735 6340
VAISALA Inc.
Handar Business Unit
1288 Reamwood Ave.
Sunnyvale, CA 94089-2233
USA
Phone int.: +1 408 734 9640
Telefax: +1 408 734 0655
Sävypaino
VAISALA GmbH
Postfach 540267
D-22502 Hamburg
GERMANY
Phone int.: +49 40 851 7630
Telefax: +49 40 850 8444
VAISALA Inc.
Columbus Operations
7450 Industrial Parkway
Plain City, Ohio 43064-9005
USA
Phone int.: +1 614 873 6880
Telefax: +1 614 873 6890