thermocouple wire lenght

Discussion in 'General' started by Bo Herrmannsen, Dec 30, 2017.

  1. Bo Herrmannsen

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    Hi

    I want to use thermocouples on my next build, are there any restrictions on how much i can shorten up the wires? 1m seems a little to much as i know that the wires are not made to be bend over and over
     
  2. Old_Tafr

    Old_Tafr Well-Known Member

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    Can you do a test? Maybe put the thermocouple in either water with melting ice in it or boiling water and check the reading?

    Shorten the wires and test.

    As the reading is based on resistance then check what it is at a set temp (room temp) and let us know.

    The higher the resistance of the device itself vs the total resistance including the wires then the less effect shortening the wires will have.

    All shortening the wires will do is cause an offset in the temp but it will still be repeatable and consistent.

    If for example the thermistor is 10k and the wires are say 1 ohm (quite likely less) then the effect will be negligible
     
  3. Bo Herrmannsen

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    i simply ask because the thermocpuples like this one: https://e3d-online.com/type-k-thermocouple-cartridge

    is very different from a thermistor when it comes to the wire... some say that the wires can break etc

    maybe i better ask the sales people about this so i dont screw up, no need to get a thermocouple if the wires cant be shortened
     
  4. dc42

    dc42 Well-Known Member

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    You can shorten the thermocouple wires as much as you want. However, it's hard to extend thermocouple wires without risking interference or inaccuracy. So it's perhaps safer to coil the unused length out of the way.

    Is there a particular reason why you want to use thermocouples? Unless you will be printing at very high temperatures, PT100 sensors are generally preferred to thermocouples.
     
  5. Bo Herrmannsen

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    Nope to high temps

    I mainly want to try thermocouples as i had thermistors fail to often, and while they are cheap to replace i dont find it that "fun" doing it every 3 months

    i know pt100 are prefered but i have read reports that they are more troublesome than thermocouples.. i know that in both cases i would need an amp board unless the electronics have a direct input for thermocouples
     

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