Siemens ULTRAMAT 23 Series - Page 30

Electrochemical hydrogen sul󹪝de measurement
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3
5
2
1
4
6
1 Gas membrane 4 Counter electrode
2 Working electrode 5 Terminal posts
3 Reference electrode 6 Electrolyte (H
2
SO
4
)
Figure 3-7 Operating principle of H
2
S sensor
The hydrogen sul󹪝de (H
2
S) enters the sensor through the di󹪜usion barrier (gas membrane (1))
and is oxidized on the working electrode (2). The reduction of oxygen in air takes place on the
counter electrode (4) as a counter reaction. The transfer of electrons can be tapped at the
terminal posts (5) as a current that is directly proportional to the gas concentration.
The zero point is automatically recalibrated by the AUTOCAL function when connecting e.g.
nitrogen or air.
Automatic calibration of the IR and UV components with air or nitrogen (AUTOCAL)
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Figure 3-8 Calibration with air
The ULTRAMAT 23 can be calibrated using, for example, ambient air. During this process (can be
set between 1 and 24 hours, 0 = no AUTOCAL), the analyzer chamber is purged with air by way
of an internal or external 3-way valve. The detector then generates the largest signal U
0
(no pre-
Description
3.3 Function
ULTRAMAT 23
30 Equipment Manual, 04/2022, A5E37100388-012