I was working with some thermistors for a recent project, I’m making a WiFi fridge sensor that sends data via MQTT, anyway, it uses a thermistor as the temp sensor and the ones I got did not come with a good datasheet. The datasheet for my part did not include any data on the temperature/resistance curve! Most good thermistors will come with the curve information in their datasheets and infact some will even include the Steinhart-Hart coefficients, but this did not. The part in question is a Cantherm MF52A2103J3470 and I had to figure out the curve on my own.
The process that I followed was to use a thermocouple I had connected to a multimeter to get known temperatures and then use another multimeter to check the resistance of the thermistor at those known temperatures. I ended up grabbing the following data points:
-26C = 96.3K
+4 = 24.1K
+39 = 5.5K
Once I had those datapoints I could drop them into this thermistor calculator: https://www.thinksrs.com/downloads/programs/therm%20calc/ntccalibrator/ntccalculator.html
The calculator then produced the following coefficients for the Steinhart-Hart equation:
A=1.221849189e-3
B=2.094372171e-4
C=2.785700391e-7
With those coefficients I was able to calibrate my thermistor to a reasonable level of accuracy!