Conductivity Sensor Types

Conductivity Sensor Types
Types of conductivity sensors
Hygienic:
Generally there are two types of conductivity
sensors:
The flat electrode assembly of a four pole
HAMILTON conductivity cell can be easily
cleaned. When assembled into a HYGIENIC
SOCKET™ (view page 38) its cleanability
complies with EHEDG criteria. That was
confirmed by the TU München (Test No 180 /
10.10.2008).
• 2 electrode sensors are constructed in a
simple way.They are suited for measurements
in clean solutions. Contaminations, e.g. by
lime, affect the measurement
• 4 electrode sensors consist of two current
and two voltage electrodes. Between the
two current electrodes there is a constant
electric current. With the two voltage
electrodes a voltage drop is measured
accross the sample. The voltage drop
depends on the conductivity of the sample.
Because of this measurement principle, 4
electrode sensors have a much broader
linear measurement range and are not
sensitive to contamination.
HAMILTON 2 electrode sensors with graphite
contacts
current electrodes
voltage electrodes
EHEDG: Sets criteria for cleanability
sample solution
Scheme of a 4 pin conductivity cell
Unique linearity:
A Conducell 4USF-PG, calibrated with a 1413 μS/cm standard solution, is capable of determing
standard solutions covering a wide range of conductivities with extremely small deviations.
1.E+06
106
The flat tip of CONDUCELL 4USF-PG
CONDUCELL
4USF-PG-120
/ Knick Stratos 2401
Conducell
4USF-PG-120
reading [uS/cm]
1.E+05
105
1.E+04
104
1.E+03
103
1.E+02
102
Tested hygiene: CONDUCELL in
HYGIENIC SOCKET™
1.E+01
101
1.E+00
100
1.E+00
100
1.E+01
101
The effect of temperature
104
105
1.E+02
1.E+03
1.E+04
1.E+05
102
103
conductivity (reference value) [uS/cm]
The conductivity of a solution strongly
depends on temperature. In order to compare
measurement results, the measurements must
refer to a standard temperature of 25°C. The
notion “Temperature compensation” means
the translation of a conductivity obtained at
any temperature to the theoretical measurand
at 25°C.
106
1.E+06
For most aqueous solutions the conductivity
changes almost linearily by approximately
2% /°C. Most conductivity sensors contain
a temperature probe to compensate for the
temperature effect. Additionally, with some
transmitters temperature compensation can
be adapted to the sample.
EHEDG 01 Reinigbarkeitstest
Prozessanschluss Hygienic Socket
am Beispiel Leitfähigkeitssensor, Typ Conducell
Test-Nr. 180 / 10.10.2008
Hamilton Bonaduz AG
CH-7402 Bonaduz
Der Bericht umfasst 11 Seiten mit 1 Seite Anhang, 4 Abbildungen und 1 Tabelle.
Die Prüfergebnisse beziehen sich nur auf die angeführten und untersuchten
Bauteile. Die Prüfungen wurden von geschultem Personal nach den angegebenen
Testvorschriften durchgeführt.
Weihenstephan,
den 02.02.2009
Report of TU München: EHEDG cleanability test
– 25 –
THE MEASURE OF EXCELLENCE
TM