The following occurs when the protection function starts:
• The H
2
S measured value display is set to "*****"
• An "H" (H
2
S protection function running) is displayed in the measurement screen at the right
edge where the test letter "!" appears (fault no longer pending has been logged).
• The zero gas valve is opened
• The "Function control" status is set.
As long as the protection function is active, the zero gas valve remains open during the zero gas
purge time. The device then switches to purging of the sample gas path with sample gas. This
process is repeated if the maximum continuous concentration is exceeded within the sample
gas purge time.
This process is repeated up to 6 times. If after the 6th repeat the sample gas concentration is still
too high, the zero gas valve remains permanently open and the fault 28 "H
2
S probe protection"
is entered in the logbook.
If the maximum continuous concentration is not exceeded again, the protection state is
terminated and the H
2
S measured value is displayed again. Furthermore, the function control
and the test letter "H" are deleted.
Return to measuring mode
An active protection function can be interrupted as follows:
• Automatic: Prior to completion of the 6th repeat, the measured value in the sample gas purge
time remains permanently below the maximum continuous concentration.
• Set the protection function to 'OFF' by changing the parameter in the limit display or via ELAN
• Start a dierent state such as calibrate, AUTOCAL, etc.
• Acknowledgment of the fault "H
2
S probe protection" in the logbook
Sequence parameter
The zero gas purge time is twice the AUTOCAL purge time. The sample gas purge time is equal
to the AUTOCAL purge time. The AUTOCAL purge time is an adjustable parameter whose setting
is described in section Calibration: AUTOCAL/drift values: Purge time (Page 126).
The protection function can be enabled and disabled using the menu item 'H
2
S probe
protection' (see section Parameters: Limits: H2S sensor protection (Page 131)). The function is
ON with the factory setting.
The device remains in measuring mode while the protection function is running. You can read
out via ELAN or PROFIBUS whether the protection function of the analyzer is being processed,
and in which step.
The following illustration show how the protection function runs over time:
Functions
8.5 Automatically executed functions of the H2S sensors
ULTRAMAT 23
158 Equipment Manual, 04/2022, A5E37100388-012
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