Removing The Thermistors; Installing The Thermistors; Thermistor Checkout - ABB PGC2000 Operation And Service Manual

3. Open the isothermal oven door.

Removing the Thermistors

1. Use a Phillips screwdriver to loosen the two Phillips head screws located on the top cover.
2. Remove the top cover by sliding it out and away from the detector assembly.
3. Remove the top sleeve from the detector assembly.
4. If they are not already labeled, label the wire pair connected to the measurement thermistor "M"
and the wire pair connected to the reference thermistor "R".
5. Position the detector wiring such that the wired splices can be accessed.
6. Cut and remove the heat shrink from each of the spliced thermistor wire connections to expose
the soldered connections.
7. Using a 40 watt soldering iron, de-solder and disconnect the wire splices.
8. Clean the area around the two detector thermistors to reduce the chance of foreign particles
entering the detector cavity when the thermistors are removed.
9. If necessary, remove the two standoffs that hold the top cover in place and retain them for re-
installation.
10. Loosen the two detector thermistor retaining gland nuts with a 5/16-inch open-end wrench.
Continue to loosen by hand.
11. Carefully extract the thermistors from the detector cell cavity.

Installing the Thermistors

Replacement thermistor installation kits are supplied with a matched pair of thermistor assemblies,
high temperature solder, and heat shrink tubing.
1. Cut the four thermistor wires approximately the same length as the wires on the thermistors that
were removed.
2. Insert one thermistor assembly into the detector cell cavity marked "M" (measurement) and screw
the cable gland finger tight.
3. Finish tightening the cable gland with a 5/16-inch open-end wrench.
4. Insert the second thermistor assembly into the detector cell cavity marked "R" (reference) and
screw the cable gland finger tight.
5. Finish tightening the cable gland with a 5/16-inch open-end wrench.
6. Using wire strippers, remove approximately 1/4 inch of insulation from the end of each detector
thermistor wire.

Thermistor Checkout

1. On a multimeter select the ohms function and a range capable of measuring 40 ohms.
8-28 2000-OSM, F1