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Tips on good calibration (for H2S)
In order to perform good calibration, follow the instructions below
1.
Make sure the flow meters are stable and are set at 1 SCFH. Not enough pressure on the
calibration gas may cause flow meter to fluctuate and will result in inconsistent flow of gas
through the sensor.
2.
If process stream is known to have high concentration of H2S then turn off the sample from
stream approximately 3 minutes (1 sample cycle) before calibration. This will allow
additional time to purge the sensor.
3.
During the sampling and clearing time of calibration always note the change in voltage and
gain factor as displayed on the last line of the LCD. The gain factor is a number that ideally
should be between 40 and 230. However, the gain factor outside of this range does not
necessarily imply the malfunction of the sensor.
4.
Also note the steady change in the sensor signal ( displayed on the last line of the LCD).
The sensor signal should rise as the sensor is exposed to H2S during the sample cycle and
should clear to zero state when in purge or clear mode. The typical zero state of a sensor is
between 0.8 and 1.1 volts.
Sensor Calibration Error
The unit will display messages if sensor calibration error occurs.
Error Message
Description
Remedy
Zero too High
Sensor is unable to clear
Check any blockage on sensor vent
lines. Also check if purging pump
is operating.
Zero too Low
Sensor drift below baseline
Sensor old or deteriorated. Replace
with new one.
No Span
Or Span too low
Sensor was unable to detect any
change
Check the H2S concentration of the
calibration gas being applied.
Also check the flow meters for
proper flow rate.
Check for possible leaks in the
tubing inside the sampling system.
If problem persists then sensor may
need to be replaced.
If the calibration fails then the analyzer will restore the old calibration data.
