Oxygen Monitor SGM7 6 Composition
HB_SGM7_eng.docx
15
6.1.2 Construction principle of the solid electrolyte sensor
1
2
5
6
7
3
4
Measurig Gas
Fig. 2:
Composition of the solid electrolyte sensor
The measuring cell (sensor) consists of a tube made of zirconium dioxide
(2/1) with two platinum electrodes. The measuring electrode is inside the
tube (2/3). The reference electrode (2/4) is located on the outside of the tube
and has a constant electrode potential. The electrodes and the ceramic tube
form a galvanic solid electrolyte measuring cell.
Measuring cell
(sensor)
In order to gain a higher oxide ion conductivity of the zirconium dioxide tube,
the sensor is heated to 750°C. This also avoids interfering reactions with
combustible components of the measuring gas at the electrode caused by
chemical unbalances. A thermocouple (2/5) inside the measuring cell
determines the actual electrode temperature. A regulator ensures a constant
temperature.
Sensor heater
The heated measuring cell produces thermal energy. Therefore, the SGM7
must not be covered.
1 Ceramic tube
2 Ceramic cover of reference
electrode
3 Measuring electrode
4 Reference electrode
5 Thermocouple
6 Connecting wire of
reference electrode
7 Connecting wire of
measuring electrode
