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Functions
8.5 Automatically executed functions
ULTRAMAT 23
156
Manual, 3/2016, A5E37100388-003
8.5.2 Probe protection function
Definition of probe protection function
A value 1.1 times the specified range can be considered as the maximum continuous
concentration. Although a measurement above such a concentration is still correct, the probe
is damaged by longer exposure. The maximum continuous concentration remains constant
even when changing the measuring range.
The protection function is also implemented with the 50 vpm probe for compatibility reasons
even though its maximum continuous concentration is 12.5 vpm. The protection function is
executed above this value.
Execution of this function is the same for all probes. The function test is set during execution
of the protection function in order to signal that the displayed value is incorrect.
How the protection function works
The protection function is triggered if the continuous measured value of H
2
S is greater than
the maximum continuous concentration (110 % of full-scale value) in measuring mode for a
period of 3 seconds.
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 different state such as calibrate, AUTOCAL, etc.
● Acknowledgment of the fault "H
2
S probe protection" in the logbook