ROC800-Series Instruction Manual
Revised July-2017 Troubleshooting 6-13
To test the thermocouple module:
1. Disconnect the thermocouple from the thermocouple module.
2. Generate the correct J or K signal using a multimeter and connect the
wiring from the multimeter to the T/C module.
3. Verify the ROC is reading the generated temperature from the
multimeter.
4. Remove the test equipment, and reconnect the field device.
To test the thermocouple:
1. Disconnect the thermocouple from the ROC800.
2. Connect the thermocouple directly to the multimeter and verify the
reading is correct by comparing it to a certified temperature
measurement device connected to the process temperature the T/C is
measuring.
3. Remove the test equipment, and reconnect the field device.
Unintentional thermocouple junctions cause many measurement errors.
Remember that any junction of two different metals will cause a
thermocouple junction. To increase the length of the leads from the
thermocouple, use the correct type of thermocouple extension wire. Any
connector must be made of the correct thermocouple material and correct
polarity must be observed.
If the reading is off:
1. The type J or K thermocouples are selected on a per channel basis on
the thermocouple module. Verify each channel on the ROC800 and
make sure it is set for the type of thermocouple that you are using.
2. Ensure any plugs, sockets, or terminal blocks used to connect the
extension wire are made from the same metals as the thermocouples
and correct polarity is observed.
3. Verify all connections are tight.
4. Verify the thermocouples have the correct construction (ungrounded)
and are not grounded by other means.
5. Verify you are using the correct thermocouple wire all the way from
the thermocouple to the ROC800 with minimal connections.
6. Verify the wiring run is adequately protected from noise.
7. Test the thermocouple reading from the thermocouple to a meter, and
then generate a signal into the ROC800 as described previously.
8. Finally, connect a thermocouple of the same type directly to the
ROC800. If it reads correctly, the problem is likely to be in the wiring
to the field or may be related to a ground loop.
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