Sanity check: I need to measure the junction temperature (or as close as possible) of an SMD LED. Can I solder the tip of a thermocouple to a leg of the part? Assuming there is no ground loop (the meter is battery operated, standalone), is there anything I should be aware of?
I am assuming that the thermocouple being in connection with the circuit will not influence the reading, is that a correct assumption? The LED is driven by a 25kHz PWM signal. I'll also be connecting another thermocouple to the metal enclosure by drilling a hole and pinching the tip in the hole.
I have tried thermal glue previously and that was a unreliable so I would want to avoid glue.
Answer
Solder a type T thermocouple to whichever pin of the LED has a better thermal conductive path to the LED die.
Type T thermocouples are copper-constantan, and are solderable, whereas the more common type J and type K are of metals that do not form a solder joint.
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