Analysis and treatment of common faults of thermocouples

Fault phenomenon
possible reason
Approach
The thermoelectric potential is smaller than the actual value (the display meter indicates a low value)
Thermal electrode short circuit
If it is wet, dry it; if the insulator is damaged, replace the insulator.
The galvanic junction of the thermocouple is short-circuited, causing a short circuit
Sweeping dust
Compensation wire short circuit
Find the short circuit point, strengthen the insulation or replace the compensation wire
Thermocouple hot electrode deterioration
Under the length of the question, cut the metamorphic section to re-weld, or replace the new thermocouple
Compensation wire and thermocouple polarity reversed
Reconnect correctly
Compensation wire does not match thermocouple
Replace the matching compensation wire
The thermocouple installation position is not recorded or the insertion depth does not meet the requirements.
Reinstall as required
Thermocouple cold junction temperature compensation does not meet the requirements
Adjusting the cold end compensator
Thermocouples do not match display instruments
Replace the thermocouple or display meter to match
The thermoelectric potential is larger than the actual value (the display meter indicates a high value)
Display instrument does not match thermocouple
Replace the thermocouple to match it
Thermocouple and compensation wire are not matched
Replace the compensation wire to match it
DC interference signal enters
Eliminate DC interference
Thermoelectric output is unstable
Poor contact between thermocouple terminal and hot electrode
Tighten the terminal screws
Thermocouple measurement line insulation damage, causing intermittent short circuit or grounding
Find the point of failure and repair the insulation
Thermocouple is not installed securely or externally vibrated
Tighten the thermocouple to eliminate vibration or take shock absorption measures
The hot electrode will be broken
Repair or heat exchange galvanic couple
External interference (AC leakage, electromagnetic field induction, etc.)
Detect interference sources and use shielding measures
Thermocouple thermoelectric potential error
Hot electrode deterioration
Replace the hot electrode
Improper installation of thermocouple
Change the installation location
Protection tube surface area gray
Clear the dust

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