NTC thermistor; arduino

Introduction

Theory

Electronics

Simple circuit

$R=R_{1}+R_{ntc}$

${\begin{cases}I&={\frac {U}{R}}={\frac {5V}{R_{1}+R_{ntc}}}\\I_{R_{1}}&={\frac {U_{R_{1}}}{R_{1}}}={\frac {V_{measured}}{R_{1}}}\end{cases}}$ Because $I=I_{R_{1}}$, we get $V_{measured}={\frac {R_{1}}{R_{1}+R_{ntc}}}5V$ or $R_{ntc}={\frac {R_{1}}{V_{measured}}}5V-R_{1}$ and $R_{ntc}$ gives the temperature. Of course, it needs to be scaled. But that is not a problem.

$\beta ={\frac {\ln {\frac {T_{1}}{T_{2}}}}{T_{1}^{-1}-T_{2}^{1}}}$

Code

Calibration

Use two fixed point calibration.

References