Connecting The Thermistors - ABB PGC2000 Operation And Service Manual

2. Connect one multimeter lead to each wire of the measurement thermistor (installed in the
detector cavity labeled "M"). The resistance measurement should be approximately 40 ohms.
3. Connect one multimeter lead to each wire of the reference thermistor (installed in the detector
cavity labeled "R"). The resistance measurement should be within one ohm of the measurement
thermistor resistance.
4. If the resistance measurements are not within one ohm of each other, ensure the multimeter is
connected and functioning correctly, and that the correct meter function is selected.
5. If the detector thermistors are not in tolerance, the detector thermistors are defective. The
matched set of thermistor assemblies must be replaced and the checkout repeated.
6. Neither thermistor should contact the detector cell body. Connect the multimeter leads to one of
the thermistor wires and the detector cell body. The meter reading should range from several
hundred megohms to infinity.
7. Repeat this measurement for each of the other three thermistor wires. If all resistance
measurements are correct, go to "Connecting the Thermistors." If any resistance is too low, go to
step 8.
8. If the resistance measurement is approximately 20 ohms, the thermistor being tested is
contacting the internal wall of the detector cell cavity. When this occurs, carefully loosen the
gland of the suspect thermistor. Continue to loosen by hand and withdraw the gland and
thermistor from the detector cell body (taking care not to touch or damage the thermistor).
9. Inspect the thermistor for damage or bending. If it is damaged, the matched set of thermistor
assemblies will have to be replaced.
10. If the thermistor is slightly bent, use small needle nose pliers to gently and carefully bend it
straight.
11. If the thermistor orientation now appears to be correct, reinstall the detector thermistor and
repeat the complete checkout. If it fails again, replace the matched set of thermistor assemblies
and repeat the harness checkout.
12. If the thermistor is damaged during this attempted correction process, the matched set of
thermistor assemblies will have to be replaced.

Connecting the Thermistors

1. Roll the ends of each stripped harness wire between your thumb and index finger to tightly spiral
wrap the wire ends.
2. Using a 40 watt soldering iron and approved high temperature solder, "tin" each of the harness
wire ends.
3. Roll the ends of each stripped thermistor wire between your thumb and index finger to tightly
spiral wrap the wire ends.
4. Using a 40 watt soldering iron and approved high temperature solder, "tin" each of the thermistor
wire ends.
5. Install approved heat shrink over each of the four thermistor wires and slide it as far from the free
wire end as possible.
2000-OSM, F1 8-29