thermocouple on copper

Discussion in 'General Electronics Chat' started by Skeebopstop, Feb 9, 2009.

  1. Skeebopstop

    Thread Starter Active Member

    Jan 9, 2009
    just curious if anyone has ever designed a thermocouple out of copper tracking?

    I was thinking along the lines of using copper and another component type metal reference to generate the temperature dependant voltage.

    would be nice to rig up something nice to be able to read out the temperature of your boards, especially when maybe sampling the ambient inside a housing in one or two spots.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    It might be a challenge to find a truly neutral bit of copper to attach a dissimilar metal to generate that thermocouple voltage. I wonder if it could be isolated so it did not create problems - odd voltage on the ground plane, creating an alternate ground path, and so on.

    I would prefer to use a thermistor for the purpose. It's usually important to control voltage sources and current paths on the PCB foil.
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    Copper-constantan is a recognized thermocouple pair. It gives (mV) of -0.67 at 0°F, 1.52 at 100°F, and 3.97 at 200°F.

    How are you going to weld the constantan to the PCB trace? I've never tried it, but capacitor discharge might work.

  4. Skeebopstop

    Thread Starter Active Member

    Jan 9, 2009
    No idea mate. My first impression would have also been to just use an SMD thermistor, but it is always interesting to see how far we can push the copper on the boards (i.e. microstrip).

    Just curious if anyone out there had any 'standard' implementations for doing this by having one half of the trace with its soldermask stripped back so the junction become copper with solder, copper without solder.