Detcon TP-624D - Manual (Page 36)

Model TP-624D
TP-624D Instruction Manual Rev. 0.4 Page 32 of 40
6. Troubleshooting Guide
Refer to the list of Failsafe Diagnostic features listed in Section 3.6.2 for additional reference in
troubleshooting activities. Listed below are some typical trouble conditions and their probable cause and
resolution path.
Figure 13 Replaceable H
2
S Sensor
Open Heater
Probable Cause: H
2
S sensor has failed
Remove H
2
S sensor wires from the Connector PCB and verify resistance between the black and white wires
using an ohmmeter. At room temperature, the heater film’s normal reading should range between 70 and 90
ohms.
Replace the H
2
S sensor if open circuit or significantly out-of range readings are found.
Open Sensor
Probable Cause: H
2
S sensor has failed
Remove H
2
S sensor wires from the Connector PCB and verify resistance between the blue and yellow wires
using an ohmmeter. At room temperature, the sensor’s normal reading range should be 100 K-ohms to 25
meg-ohms. Failure would be open circuit.
Replace the H
2
S sensor if an open circuit is found.
AutoSpan Calibration Faults – (Range, Stability, and Clearing)
To clear any AutoSpan Calibration fault, the AutoSpan process must be completed successfully (Section3.4).
Range Fault
Probable Causes: Failed Sensor, Cal Gas not applied or not applied at appropriate time, problems w/ cal gas
and delivery, no Humidifying Tube used, failure to properly desiccant packet the sensor cell during extended
power-off periods.
Check Heater Power Setting (should be 240 ± 5mW at 25ºC ambient temperature).
Verify use of span gas Humidifying Tube.
Check validity of span gas using H
2
S pull tube or other means (check MFG date on cal gas cylinder).
Check for obstructions through stainless steel flame arrestor (including being wet, blocked, or corroded).
Replace the H
2
S sensor.