DualKmeter Measurement Problem
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My project is to modify a small hotplate (BYA-1010) for SMD reflow soldering.
I am using the original controller board for its 5V power supply and Triac circuitry. I have disabled the microcontroller. I am controlling the hotplate with an M5Stack Basic and am using a DualKmeter 13.2 module and a thermocouple for temperature sensing. The actual hotplate itself is made of aluminium and is grounded for electrical safety. The 5V power supply is not grounded.
If I touch the thermocouple onto the plate the DualKmeter gives a Not Ready (ie Fault) status. The same thing happens if I use the original factory-fitted thermocouple, which is screwed to the underside of the plate
However, if I use a Kmeter ISO Unit (connected to the Grove port of the M5Stack Basic) this does not happen and I get valid temperature readings. Can somebody explain this? The DualKmeter thermocouple input circuit is supposed to be galvanically isolated, so this should not happen. The Kmeter ISO Unit is behaving as expected.