Zirconia Probes
for the Simultaneous Measurement
of Oxygen and Combustible Gases -
The Sensors
 Product Sheet
The Sensors
The Dual Sensor
The Oxygen-sensing Part
The COe-sensing Part
Technical Data
Probes
Electronic
Controller AMS 3220 - Twin-version
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The Dual Sensor
The dual sensor for simultaneous measurement of O2 and COe looks very similar to our standard O2-sensor, but is distinctively different:
It contains a standard Platinum-(Pt-)-electrode for O2 measurement and a separate electrode, made from an alloy of Pt with another noble metal for the measurement of COe.
The reference electrode for both measuring electrodes is the inner Pt-electrode, exposed to the reference gas (usually instrument air).
The sensor has been developed by LAMTEC Corp. (Walldorf, Germany)
The Oxygen-sensing Part
This part of the sensor operates according to Nernst’s principle for solid state electrolytes:
At a constant operating temperature and constant Oxygen concentration in the reference gas, the masuring signal for O2 in the sample gas is described as:
Legend:
US sensor signal in mV
A change of sensor signal for a change of
O2-concentration by a factor of 10
B sensor offset for COxygen-sample-gas = COxygen-reference-gas
The COe-sensing Part
Combustible gas molecules will be adsorbed at the electrode (similar to O2-molecules) and reach the three-phase-barrier of sample gas, electrode and Zirconia.
The reaction at the COe-sensitive electrode produces an additional signal to the O2-signal.
Even at very small concentrations of combustible gases like CO or H2, this signal exceeds the O2-signal considerably.
The formation of this signal is very fast : T60-times of 2 seconds are common.
The Oxygen concentration has quite some influence on the COe-signal. It is therefore vital to correct the signal for the O2-concentration measured.
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