PLC / Analog Signals & Measurement Quality
Investigate a temperature error caused by the wrong thermocouple type
A thermocouple input can produce a changing yet incorrect temperature if its configured type or extension materials do not match the sensor.
Environment and inputs: Industrial PLC / automation guidance · Verify the exact controller, module, firmware, engineering tool and machine documentation. Linked vendor examples apply to their stated products and library versions; observation, state changes and physical work require distinct authorization.
Observe and record
Compare the sensor specification, module channel mode and approved extension-cable or connector identification from maintenance records.
Interpret the evidence
Different thermocouple types have different voltage-temperature relationships. A plausible ambient reading does not prove accuracy across the operating range.
Resolve and verify
Have the instrument owner correct the approved type and compatible installation, then validate several relevant temperatures through the calibration procedure.
Machine and data safeguards
Do not substitute generic wire, change polarity by guessing or disconnect a live protective temperature loop informally.