Hermocouple Checks - Ametek Dycor CG1100 Series User Manual

Thermocouple Checks
Thermocouple Checks
Reversed Thermocouple
Wires
Cell temperature will display a
negative number on the Status tab
of the configurator software if the
thermocouple wires are reversed.
Wiring Checks
Open Thermocouple
Disconnect power to the analyzer. Disconnect TB5 plug from
the analog board and measure the resistance across the
terminals. If an open is measured, replace the thermocouple.
Shorted/Failed Thermocouple
check that the thermocouple leads are not shorted to chas-
sis ground. Disconnect the TB5 plug from the analog board
and using an ohm meter, measure the resistance between
Tc+ terminal and chassis ground, and between terminal Tc-
and chassis ground. If shorted, replace the thermocouple.
Checking Continuity
Measure the resistance across connections Tc+ and Tc-
across TB5 terminals on the analog board. The resistance
should be less than 5 ohms.
If this doesn't solve the problem:
Remove the thermocouple from the analyzer and connect
it to a Type K test meter. using a thermometer, check the
temperature of an environment. Place the thermocouple in
this same environment and check that the reading of the test
meter measures the same temperature as the thermometer.
If the thermocouple measures the temperature incorrectly (greater
than 1% of expected temperature), replace the thermocouple.
Thermocouple Compensation Circuit Check
use a volt meter to measure across capacitor TB5 on the
analog board. if you measure 1 millivolt at capacitor TB5,
measure across connections labeled Tc- (TB5, Pin 2) and
cell- (TB4, Pin 2) on the analog board. it should measure 1
millivolt at 25°c ambient temperature. This signal is a function
of ambient temperature and may be up to ±2 millivolts at extreme
ambient temperatures. At 0°c the reading should be 0 milli-
volts, and at 40°c it should read 1.6 millivolts.
If you don't measure this voltage, replace the backplane board
Make sure all wiring connections are terminated to the
proper locations and are seated properly. Ensure wires are
not reversed and the cable is not damaged.
Maintenance and Troubleshooting | 6-3T