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3.3.4. Fault thresholds
Processing of detector faults
Each channel detects the following faults.
For toxic and explosive gas detectors:
- line interrupted (0 mA),
- line short-circuited or excessive consumption,
- negative offset (more than 20% of measuring scale),
- line in calibration mode (2 mA) (if confirmed by programming).
For detectors of the explosive gas type (4-20 mA and 340 mA) in normal mode and if the
measurement is greater than 100% of the measuring scale, there are the following immediate
results:
- Display: SUP
- The relays are actuated if the thresholds are reached.
- The general fault relay is actuated.
- The 4-20 mA output of the channel is greater than 20 mA.
- All these states are memorized and the only way of acknowledging them is to
switch off the channel and then restart it.
Faults are valid after a preprogrammed time (in the same way as alarms).
FAULT BLOCK DIAGRAM
END
START
Wait until the fault has been present
for at least 5 seconds.
The relays are locked in their current state.
The common fault relay is engaged.
The buzzer is engaged.
The channel fault LED is illuminated. *
1 mA is sent on the 4-20 mA output.
* The LED is extinguished as soon a the fault disappears.
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