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I am trying to measure the surface temperature of a cold plate using K-Type thermocouples. However, the temperature reading on the scope is fluctuating tremendously.

IGBTs are attached on the cold plate and current is passing through them. The TCs are secured onto the cold plate surface using Kapton tape. The readings are fluctuation between 10 degrees and 45 degrees. The ambient temperature of the room is 26 degrees and the coolant is at 30 degrees. Which makes the reading inaccurate.

When I secure the TC to a non metallic surface, the readings do not fluctuate irregularly. Is there anything that I'm doing incorrectly? Thanks.

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  • $\begingroup$ Since IGBTs are power devices, I'd guess that the thermocouple is picking up interference from them, or the associated power wiring; does the problem go away when that circuitry is turned off? $\endgroup$
    – jayben
    Commented Mar 3, 2022 at 11:22
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    $\begingroup$ sounds like you need to isolate the thermocouple system. it may be picking up something like case ground at the bead. if that same case ground is then used as a reference in the same system attempting to measure voltage over the wires, then it won't work. $\endgroup$
    – Abel
    Commented Mar 4, 2022 at 2:09
  • $\begingroup$ You will probably need to electrically isolate the thermocouple. If that's not possible, you may be able to isolate the thermocouple reading electronics, but that will be much more complicated, and probably won't work as well. $\endgroup$
    – Drew ♦
    Commented Mar 5, 2022 at 7:54

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