Designing with Thermistors

Temperature-Sensitive Resistors

Thermistors are a useful electronic component as a simple way to measure temperature.  It acts just like a normal resistor, except that the resistance varies as the temperature rises and falls in a predictable manner.

This is a typical "10K" thermistor that you can buy from Adafruit

Thermistor

Now, since this is a thermistor, and not a normal resistor, its not 10k all the time, but 10k at a specific (and as it happens, standard) temperature of 25º C.  It comes with a datasheet that shows how its resistance varies with temperature.

There is a curious set of constants at the top of the datasheet, as you can see highlighted here

These two constants define the constants needed to complete what is called the "characteristic equation" for this particular thermistor.