A7.8
3.10.6.3 Zero Gas Flow Failure - 63
Indicates that the analyser has not detected a change in oxygen reading within a preset time
interval after switching on the zero gas.
This may be due to:
1. No zero gas or low flow.
2. Preset time intervals too short. Perform a manual calibration and measure DV lag and
90% point on a chart recorder.
The time out period for the DV lag is in Parameter 49 and for the 90% point in parameter 50. This
alarm can only be cleared by performing a successful auto-calibration.
3.10.6.4 Span Gas Flow Failure - 64
Identical to zero gas flow failure (Section 3.10.6.3). The time out period for the DV lag is in
parameter 52 and for the 90% point in parameter 53.
3.10.6.5 Sample Gas Flow Failure - 65
Identical to zero gas flow failure (Section 3.10.6.3). It usually indicates a fault within the sample
system. A manual calibration should be done to determine which calibrating point is in error.
This alarm can only be cleared by performing a successful auto-calibration.
3.10.7 Oxygen Level Alarms In Auto-Calibration
The oxygen level alarms will be triggered by the change in the oxygen signal as a result of the
calibrating gases passing through the analyser. The user can make use of the auto-calibration
alarm (46) and external logic functions to inhibit any external annunciators.
3.10.8 Electrical Power Failure In Auto-Calibration
Assuming that the battery back-up of memory is good, then should electrical power fail during the
auto-calibration sequence, when the analyser restarts the sequence is aborted and the previous
calibration is still valid. The next auto-calibration will occur at the programmed time interval after
the restoration of power.
If the power interruption occurs during normal operation then the clock which controls the auto-
calibration repetition time is stopped but its settings retained in memory. When electrical power
is restored the clock starts running again but the next auto-calibration will be delayed by the
duration of the power interruption.
If the battery back-up of memory has failed then the complete memory is erased and the analyser,
including auto-calibration functions, will have to be reprogrammed.
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