a digital ohmmeter. The resistance and corres pon ding temperature is lis t ed in Table 11A or
Table 11B. Check the r es i stance of both wires to ground. This resistance should be infinite.
Voltage Drop
Using a digital voltmete r, the voltage drop acros s any en ergized sensor can be me as ur e d
while the control is ene r giz e d. Table 11A or Table 11B l ists the relat ionship between
temperature and sensor v ol tage drop (volts dc measu red across the energiz ed sensor).
Exercise care when measu ring voltage to prevent damage to the sensor lead s, connector
plugs, and modules. Sen sors should also be chec k ed at the sensor plugs. Check th e sensor
wire at the sensor for 5 vdc if t he c on trol is powered.
Check Sens or Accuracy
Place the sensor in a mediu m of a known temperature and compare that temperat ur e t o the
measured reading. The thermometer used to det er m in e the temperature of the medium should
be of laboratory quali ty wi th 0.5° F (.25° C) gradua tions. The sensor in que s ti on should be
accurate to within 2° F (1. 2° C).
CAUTION CAUTION
!
Relieve all refriger an t pressure or drain the w at er prior to replacing the temp era-
ture sensors.