Troubleshooting of thermocouple assembly?

Prefabricated thermocouples have a wide range of applications, but some malfunctions are inevitable during use. When maintaining assembled thermocouples, it is also important to know some common troubleshooting methods. Below, we will introduce the troubleshooting of prefabricated thermocouples.

1： The thermoelectric potential is greater than the actual value

Possible reasons: The compensation wire does not match the thermocouple model; Insufficient insertion depth or incorrect installation position; Thermoelectric electrode deterioration; There is interference signal entering; The reference temperature of the thermocouple is too high.

Solution: Replace the compensating wire with the same model; Change the installation position or insertion depth; Replace the thermocouple; Check the interference source and eliminate it; Adjust the reference temperature or make corrections.

2： The thermoelectric potential is smaller than the actual value

Possible reasons: short circuit; Short circuit between terminals in thermocouple junction box; Compensation wire short circuited due to insulation burnout; Compensation wire does not match thermocouple; Compensate for the polarity reversal between the wire and the thermoelectric dipole; Insufficient insertion depth and incorrect installation position; The temperature at the cold end of the thermocouple is too high.

Solution: If it is caused by moisture after inspection, it can be dried; If the insulation of the ceramic tube is poor, it should be replaced; Open the junction box and brush the wiring board clean; Re insulate the short circuit or replace it with a new compensating wire; Replace with the same type of compensating wire; Reconnect correctly; Change the installation position and insertion depth; Replace the connecting wire of the thermocouple with a compensating wire to move the cold end away from the high temperature zone.

3： The measuring instrument indication is unstable, sometimes intermittent, sometimes high and sometimes low

Possible reasons: Poor contact of the thermoelectric electrode at the terminal post; Thermocouples have intermittent short circuits or intermittent grounding phenomena; The thermoelectric electrode has been broken or appears to be broken but not broken; The thermocouple is not securely installed and is swinging; The compensating wire has grounding or intermittent short circuit phenomenon.

Solution: Reconnect; Remove the thermoelectric electrode of the thermocouple from the protective tube, identify the fault point and eliminate it; Replace with a new electrode; Firmly installed; Identify the fault point and eliminate it.