Electrolysis Device SGM5EL Operation
25
D. Calibration
CALIBRATION
206400 ppm
ZERO GAS:
206400 ppm
CALIBR. ZERO POINT:
OK ( 5.6)
SPAN GAS:
1 ppm
CALIBR. SPAN GAS:
OK ( 1.00)
6
5
START/SAVE RETURN
8.3 Calibration
For measurements with high accuracy requirements a calibration is highly
recommended (The high stability of the combi cell requires one check-up per
year only!).
The device must be in operating state for a
minimum of two hours before the calibration!
8.3.1 Zero calibration
The zero calibration serves the balance of the offset voltage of the ZrO2-
sensor. The offset is caused by the construction (when the electrode has a
disadvantageous position in the heating field) and can occur due to aging of
the sensor.
Before calibration, the sensor is flushed with ambient air. The gas flow is set
by internal or external pump at the value which is used for measuring the
measuring gas.
With the zero calibration, the working point in ambient air is calibrated with
20.64 vol.% O2.
8.3.2 Span gas calibration
Certified test gas (oxygen concentration near future measuring conditions)
must flow through the device.
The stability of the measuring value is checked during the calibration. The
real calibration process starts as soon as the signal produced by the test gas
is stable. Therefore, the duration of the calibration process can vary (variation
under 1 % in 4 seconds).
If the stability is not given, the calibration is stopped after 60 seconds.
Furthermore, the deviation of measuring value from set value is evaluated.
At zero point calib/- 20 mV (cell voltage), at span gas calib/-
20 % of measuring value (cell voltage) are allowed.