a digital ohmmeter. The resistance and corresponding temperature is listed in Table 11A or Table 11B. Check the resistance of both wires to ground. This resistance should be infinite.

Voltage Drop

Using a digital voltmeter, the voltage drop across any energized sensor can be measured while the control is energized. Table 11A or Table 11B lists the relationship between temperature and sensor voltage drop (volts dc measured across the energized sensor). Exercise care when measuring voltage to prevent damage to the sensor leads, connector plugs, and modules. Sensors should also be checked at the sensor plugs. Check the sensor wire at the sensor for 5 vdc if the control is powered.

CAUTION ! CAUTION

Relieve all refrigerant pressure or drain the water prior to replacing the tempera- ture sensors.

Check Sensor Accuracy

Place the sensor in a medium of a known temperature and compare that temperature to the measured reading. The thermometer used to determine the temperature of the medium should be of laboratory quality with 0.5° F (.25° C) graduations. The sensor in question should be accurate to within 2° F (1.2° C).

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Carrier PC211 specifications Voltage Drop