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Thread: PT100 Temperature Probes

  1. #1
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    PT100 Temperature Probes

    (I'm new to HeaterMeter and the forums, and I'm also not an electrical/software engineer, so excuse any stupid questions)

    So my current understanding is that the HM does not accept PT100 (or other RTD) probes, and only accepts thermistors or thermocouples if you have the add-on board, has anyone managed to adapt the HM to use RTDs? I have a stash of them at home that I've used for other projects, and I'd love to use them instead of needing to buy new probes.

    I have some mad-scientist ideas about how I might be able to make it work with some different add-on boards, but I'd rather avoid that if someone else has been successful with this already.

    Thanks!

  2. #2
    TVWBB Honor Circle Bryan Mayland's Avatar
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    You should be able to hook it up, if you can make an analog amplifier for it. The only problem I can see is with the offset because the circuits I see with a quick google are ~4mv/C and -276.5C. HeaterMeter can only do a -127 degree offset so it would always read 148C high. There are probably other circuits you can find with a different offset though.

    HeaterMeter take any linear analog input and calculate a temperature from it, given the mV/C and an offset between -127 and 128 degrees. Note that I say degrees when I mention the offset because it is applied at the end, after conversion from C to F if you're doing F. If your temperature units are C, then you get the full 128C of offset, but if you have Farenheit units you can only adjust it by 5/9 * 128F = 71C.
    I'm that HeaterMeter guy what ruins everybody's free time.

  3. #3
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    I'm in the same situation, I have several PT100 probes to my disposal, and would like to use them with the HM (v 4.3 that I'm currently building).
    I came across several "Digital MAX31865 PT100 RTD Amplifier Temperature Thermocouple Sensor For Arduino" interface board on ebay and other places, and wonder if I could use this as interface? Would the temperature offset still be a challenge? or can this be fixed in a piece of code somewhere.
    Thanks in advance for you help, I'm discovering this very interesting project.

  4. #4
    TVWBB Honor Circle Bryan Mayland's Avatar
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    No the MAX31865 won't work because it is a digital protocol and HeaterMeter wants to take an analog reading so the code would have to be rewritten to support it.
    I'm that HeaterMeter guy what ruins everybody's free time.

  5. #5
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    Thanks Bryan, I missed that part. I have seen that there are some analog PT100 amplifiers available, butt seen the price and the issue with the temperature offset, I think I will buy some Temoworks pro probes to get started.

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