Detcon FP-524HT - Manual (Page 18)

dropped to 0 mA until the Fault is corrected.
Fail-Safe/Fault Supervision
Model FP-524HT MicroSafe™ sensors are programmed for fail-safe operation. Any of the following fault condition
will illuminate the fault LED, and cause the display to read its corresponding fault condition: “SENSOR
FAULT” , “SIGNAL FAULT” , “HEATER FAULT”, or “CAL FAULT” . A “Sensor Fault”, “Signal Fault”, “Cal
Fault”, and “Heater Fault”, will also cause the mA output to drop to zero (0) mA.
Sensor Life
The sensor life feature is a reference based on signal output from the sensor cell. When a sensor life of 25% or less
remains, the sensor cell should be replaced within a reasonable maintenance schedule.
3.11 D ISPLAY C ONTRAST A DJUST
Model FP-524HT MicroSafe™ sensors feature a 16 character backlit liquid crystal display. Like most LCDs, charac-
ter contrast can be affected by viewing angle and temperature. Temperature compensation circuitry included in the
MicroSafe™ design will compensate for this characteristic, however temperature extremes may still cause a shift in
the contrast. Display contrast can be adjusted by the user if necessary. However, changing the contrast requires that
the sensor housing be opened, thus declassif ication of the area is required.
To adjust the display contrast, remove the enclosure cover and use a jewelers screwdriver to turn the contrast
adjust screw located beneath the metallic face plate. The adjustment location is marked “CONTRAST”. See f igure 6
for location.
3.12 T
ROUBLE
S
HOOTING
G
UIDE
Sensor Fault
1. Open Sensor – broken wire or contact in sensor.
2. Remove replaceable sensor element and check adjacent pin pairs with ohm-meter. Normal reading is 1-4 ohms
and failed reading is an open circuit.
3. Replace sensor if verif ied as Open Sensor.
Heater Fault
1. Open sensor or drifted heater voltage setting.
2. Check heater voltage setting and re-adjust to target reading. Unplug/replug transmitter to see if Fault clears.
3. Remove replaceable sensor element and check adjacent pin pairs with ohm-meter. Normal reading is 1-4 ohms
and failed reading is an open circuit.
4. Replace sensor if verif ied as Open Sensor.
Signal Fault
1. Zero has drifted too far negative.
2. Re-zero sensor in clean air.
Poor Sensor Performance (Slow Response, Drifting Sensor)
1. Check that correct Heater Voltage is applied to your Sensor.
NOTE: Detcon has two version sensors: C-Style and the J-Style. Each uses a different heater voltage setting.
The C-Style sensor measures 0.9”across the exposed stainless steel sinter face and has a serial number format C??-
###. The C-Style sensor requires 2.7 VDC.
The J-Style sensor measures 0.4”across exposed the stainless steel sinter face and has a serial number format J??-###.
The J-Style sensor requires 2.2 VDC.
2. If heater voltage is incorrect, adjust accordingly for the correct sensor type.
Excessive Span Drift or Slow Response
Model FP-524HT Combustible Gas Sensor PG.18