PT100 temp probe not linear in measuring

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johnzbesko
 
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Joined: Wed Jan 09, 2013 12:34 pm

PT100 temp probe not linear in measuring

Post by johnzbesko »

Noobie question here. I have a PT100 3 wire temp probe connected to a MAX31865 that is connected to a RasPi. I can calibrate it to an analog thermometer, by modifying this python call:

mash = adafruit_max31865.MAX31865(spi, csm, rtd_nominal=100, ref_resistor=422.5, wires=3)

But as the temperature changes (I measure a range from 120F to 170F, for beer brewing), the probe and analog get out of sync. I thought of using https://github.com/drhaney/pt100rtd but am unsure how to use an Arduino library in my Spyder Python IDE, even though I realize the adafruit_max31865 library is originally an arduino library. (This project is one I'm returning to after a few years.) Can someone point me in the right direction?

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johnzbesko
 
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Joined: Wed Jan 09, 2013 12:34 pm

Re: PT100 temp probe not linear in measuring

Post by johnzbesko »

Well, I think I understand why I was having so much trouble with reading an accurate temperature. My probes are actually 2 wire, not 3, even though I wired my device as if they were 3 wire. As for using the table lookup in the arduino library, table lookups can easily be implemented in python. I'm ordering new probes now.

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