arofarn/Adafruit_MicroPython_MAX31685
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Merge pull request #9 from CapableRobot/low_temp_fix

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Fix for below 0C measurements with nominal resistance other than 100 ohms
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Kattni
2020-01-08 09:43:28 -05:00
committed by GitHub
parent 95bc5592a2 207e1f7e2e
commit 17c638c02b
1 changed files with 5 additions and 0 deletions
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adafruit_max31865.py
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@ -246,6 +246,11 @@ class MAX31865:
temp = (math.sqrt(temp) + Z1) / Z4 temp = (math.sqrt(temp) + Z1) / Z4
if temp >= 0: if temp >= 0:
return temp return temp
# For the following math to work, nominal RTD resistance must be normalized to 100 ohms
raw_reading /= self.rtd_nominal
raw_reading *= 100
rpoly = raw_reading rpoly = raw_reading
temp = -242.02 temp = -242.02
temp += 2.2228 * rpoly temp += 2.2228 * rpoly