What you'll learn
**Reported symptom:** The indicated temperature falls when the process heats up and rises as it cools.
Lab time: ~10 minutes.
Lesson briefing
Reversed Thermocouple Polarity
Reported symptom: The indicated temperature falls when the process heats up and rises as it cools.
The circuit was commissioned from a known-good drawing. Treat every terminal as suspect, but test from source to load instead of guessing. Use voltage mode on an energised control circuit and continuity only after the simulated circuit is isolated.
Your task
Verify sensor polarity at the input card against the thermocouple type and extension-wire markings.
Choose the fault category only when the measurements support it.
Hints
Do not rely on generic red/black conventions; thermocouple colours vary by standard and type.
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This lesson uses 7 placed components on the lab canvas. Components are vendor-neutral (no proprietary trademarks); the wiring rules apply to any equivalent industrial part.
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