Thermocoupler and MAX31855 calibration ?



  • Anyone done anything with this ??

    At room temperature it fluctuates up to +5 (c).

    Measure with the probe in the fridge at -18(c), +9(c) It hit's the -18 after around 30min, but settles after another 30min at -9
    Is there a Thermocouple lib with build in correction ??
    Screenshot 2015-03-20 12.05.05.png


  • Admin



  • Nope, using the Adafruit.. Will try this !!



  • That lib only supports HW SPI(from what I can see) and I would need it for Pro Mini's. But tried it on a mega, almost same issue.
    Did some more testing with same result. I checked the datasheets , and from what I can see, it is depending on a stabel reference voltage.
    Was driving my pro mini with 5v and then regulating it to 3.3v for the MAX31855. So dataline was 5v and max31855 was 3.3. Even if this is within spec the macx31855 board I got was as cheap one, so it did not filter the voltage/data input for the chip.(Looks like the Adafruit board does?) Moving the regulator in front of it all, driving everything with 3.3v it's as stabel as could be expected.

    Screenshot 2015-03-21 09.41.14.png
    Green is a DS18B20, Blue a DHT21 and the black is the ThermoCoupler.


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