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Chapter 9

Thermistor

This module provides a function to calculate the temperature of a
thermistor using an exponential model for NTC (negative temperature
coefficient)thermistors.

## 9.1 Usage

To use the thermistor function, use this:

#include <thermistor.h>

## 9.2 Functions

`float thermistor_t2_at_r2(float beta, float t1, float r_t1, float r_t2)` *function*

This function uses an exponential model for NTC thermistors to
approximate the thermistor’s temperature from its resistance. This
function returns a thermistor’s temperature given the thermistor’s
β value, `beta`, the nominal resistance,
`r_t1`, at the nominal temperature, `t1`, and the
measured resistance, `r_t2`. The temperatures must be in an
absolute temperature scale; e.g., Kelvin. The equation used is:

## 9.3 Caveat

Generally, this model is not as accurate as a table lookup can be.
The measured temperature should fall within the range that the β value was calculated for, and if you have a choice of β values,
you should choose the β value calculated over the smallest range
that still suits your expected temperature range.

Also, this module uses floating calculations and `log()` to
perform its calculation. The floating-point library is large and
floating point calculations can be relatively slow.