NTC continued, it needs to be calibrated


So far, the NTC thermometer was working fine at about 20 C
But i noticed that when the actual temperature was going down (it is winter after all), the reported temperature not so much

So time to use high quality testing equipment: Put the whole thing in the fridge
A normal fridge is about 4  or 5 degrees C

Reported temp : 9 Degrees.

Something is wrong there.
Let's compute the actual beta of the NTC.

Put a voltmeter in Ohm mode at the NTC in the fridge for a bit at 5 degrees :
Result= 218 kOhm


Beta = T*Tref*ln(Rref/R)/(T-Tref)
with
T=5+K  (K=273.15)
Tref=25+K
Rref=100kOhm
R=218kOhm

=> Beta= -3230

So not really -3950

With the actual beta value,  it works much better

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