Lamtec LT 2 - Page 81

8 Fault Analysis/Trouble-shooting
79
8.2.2 Offset voltage outside the limits
An impermissible voltage U-O
2
was discovered during offset calibration. Check
whether the O
2
measuring cell has been supplied with air.
- Sufficient flow of compressed air/instrument air
Pressure rise greater than 1...2 mbar; see 6.1.2
- Cracked filter insert?
If OK, check the probe voltage U-O
2
in air.
Permitted voltage range -20…+20mV.
Reversed polarity of probe terminals 33/34
8.2.3 No reference air (can be output as a fault via P395, initiation time 1 hour)
This warning also appears if the reference air is monitored by a flow meter with limit
transducer (e.g. with the efficiency calculation optional extra 657R0895K, see section
4.12.2)
The reference air does not reach the quantity required for flowing around the
reference electrode.
This can result in the falsification of the measurement value.
Possible causes:
- There is no instrument air (compressed air, reference air pump) at the
reference air connection of the probe.
- The reference air throttle is not open sufficiently.
- The signal from the differential pressure sensor has drifted.
Measures:
- Check electrical and pneumatic connections
- Reset the reference air quantity, see 10.4
- Faulty differential pressure sensor? → replace
- Faulty pressure input card → replace
8.2.4 D-P offset calibration too low, not enough gas (compressed air)
Rise in pressure in preliminary filter during offset calibration with insufficient
compressed air (<0.5mbar).
Possible causes:
- There is no instrument air (compressed air) at the test gas connection of the
probe, or inadequate pre-pressure (0,3bar)
- The shut-off plug valve in the PCB is not open.
- The test gas throttle in the PCB is not open sufficiently.
- The signal from the differential pressure sensor has drifted (recalibrate to “0”).
- Probe preliminary filter cracked or broken (replace)
8.2.5 D-P offset calibration too high, dirty preliminary filter
Rise in pressure in preliminary filter during offset calibration with excessive
compressed air.
Possible causes:
- Instrument air (compressed air) at the probe test gas connection has
excessive pre-pressure.
- The signal from the differential pressure sensor has drifted (recalibrate to “0”).
- Probe preliminary filter is dirty (clean it)