Det-Tronics PIR9400 PointWatch Infrared Hydrocarbon Gas Detector - Manual (Page 25)

23 95-8440 9.3
Current Level Status Corrective action
2.4 to 3.9 mA Negative Zero Indication NOTE: This phenomenon is typically caused either by the presence
of background gas during zero calibration, or by condensation on the
device optics. If low level background hydrocarbon gas was present
during calibration, the result will be a signal output level below
4 mA
when the background gas clears. To correct this, the device must be
re-calibrated with all background gas removed. Purge the detector
optics with Det-Tronics “zero air” calibration gas for about
30 seconds
prior to initiating calibration.
In outdoor environments having high humidity coupled with rapid
temperature swings, very small amounts of condensation may form on
the optics, causing a temporary (up to a few hours) negative excursion
below
4 mA. This phenomenon typically does not cause a loss of
detection capability, and will self-correct as the heated optics dry out
the residual condensation. Excursions down to the
3.0 mA level may
occur without significant loss of detection capability; therefore, it is
recommended that “zero drift” alert messages should be set no higher
than
3.0 mA, with typical threshold settings between 2.4 and 3.0 mA.
The PIR 9400 hydrophobic filter offers significant protection against
condensation. Verify that the hydrophobic filter is properly installed
and not crumpled or distorted to prevent a direct humidity path into the
device optics.
1.6 mA Calibration fault Make sure that the calibration gas being used matches the Gas
Selection Switch setting. If these match and the fault is still present,
perform disassembly and cleaning procedure, then recalibrate.
1.0 mA Fouled optics Perform disassembly and cleaning procedure, then recalibrate.
0.8 mA +24 Vdc line low (less than +17.5 Vdc) Ensure that input voltage is correct and that power connections are
good. If fault does not clear, replace the electronics assembly.
0.6 mA Calibrate input active at power-up Ensure that calibration line is not shorted and that the calibration switch
is open. If fault does not clear, replace the unit.
0.4 mA Active channel fault Replace electronics assembly.
0.2 mA Reference channel fault Replace electronics assembly.
0.0 mA CPU system fault, warmup Ensure that power is applied and that the warmup period is complete
(
1 minute). If fault does not clear, replace the unit.
Table 5—Troubleshooting Table