Design And Function - ProMinent DULCOTEST CDE Serie Instrucciones De Servicio

Design and Function

3
Design The CDE chlorine dioxide sensor is a diaphragm-covered dual electrode
measurement sensor. It essentially consists of the diaphragm cap and the
electrode shaft. The diaphragm cap filled with electrolyte forms the
measuring chamber. The sample water and gases enter the measurement
chamber, into which the electrodes in the electrode shaft project, through a
micro-porous diaphragm in the diaphragm cap. The amplifying electronics
are situated above the electrodes in the electrode shaft, above which is
located the two-wire interface.
The gauge for temperature compensation is integrated in the lower end of the
electrode shaft.
Function The chlorine dioxide passes through the diaphragm into the measuring
chamber and makes contact with the collector (working electrode). At the
collector, the chlorine dioxide absorbs electrons that originate from the
counter-electrode. The counter-electrode also acts as a reference electrode.
The following electrode reactions take place:
CIO
Anode (counter-electrode/reference system)
5 Ag ➝ 5 Ag
The sensor shows practically no cross-sensitivity with chlorine (< 2 %) so it
can also be used to measure chlorine dioxide in solutions containing chlorine.
When voltage is applied between the collector and the counter electrode, the
so-called polarisation voltage, a current flows between the two electrodes.
This current is proportional to the chlorine dioxide concentration in the
sample liquid. Electronic amplification transforms the current into a standard
output signal (4-20 mA). The signal is temperature-compensated by a
temperature sensor located in the sensor shaft.
Application range The type CDE 2 is typically used in disinfection of drinking water and utility
water of breweries. The type CDE 3 is used in the chlorine dioxide treatment
of hot water of quality similar to drinking water up to 60 °C (e.g. combat
against legionellae). The CDE should not be used in liquids containing
surfactants or surface-active substances. These conditions characterise
bottle washing machines. If ClO
this situation, ProMinent can supply a specially designed measuring sensor
with type CDP.
20
Design and Function
➝ CI
- + -
+ 5e + 4H + 2H
2
+ -
+ 5e
O
2
measurement and regulation is required in
2
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