Is my CHT probe reading correctly?

Is my CHT probe reading correctly?

If you are unsure whether your CHT Thermocouple probe is reading correctly (MGL Avionics type-K thermocouple), there are a few simple tests you can do:

BOILING WATER TEST

With the CHT probe still connected to the instrument, hold the probe ring in a pot of rapidly-boiling water. You should get a reading of around 100 deg C / 212 deg F on the instrument.


MILLIVOLT TEST

To check the probe as a loose item, hold the probe ring in a pot of rapidly-boiling water. Set multimeter to millivolt scale. Due to lack of compensation in the measurement (function of instrument) the result will vary quite a bit but you should get around 3-5mV at 100 deg C / 212 degF.


CHECK POLARITY

Note that the polarity of Type-K Thermocouples is not intuitive, as Red is Negative:

TYPE-K (typical):
YELLOW = POSITIVE
RED = NEGATIVE

Note that the polarity of Type-J Thermocouples is not intuitive, as Black is often Positive:

TYPE-J (typical):
BLACK = POSITIVE
WHITE = NEGATIVE

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