# Electronic – How to measure temperature using a NTC thermistor

thermistor

I have a TTC103 NTC thermistor. It has zero-power resistance of 10 kΩ at 25°C and B25/50 value of 4050. How do I use it to measure temperature?

NTC (negative temperature coefficient) thermistors change their effective resistance over temperature. The most common equation used to model this change is the Steinhart-Hart equation. It uses three coefficients to characterize the NTC material with great accuracy.

The Steinhart–Hart equation is a model of the resistance of a semiconductor at different temperatures. The equation is:

$${1 \over T} = A + B \ln(R) + C (\ln(R))^3$$

where:

• $$\T\$$ is the temperature (in kelvins)
• $$\R\$$ is the resistance at $$\T\$$ (in ohms)
• $$\A\$$, $$\B\$$, and $$\C\$$ are the Steinhart–Hart coefficients which vary depending on the type and model of thermistor and the temperature range of interest. (The most general form of the applied equation contains a $$\(\ln(R))^2\$$ term, but this is frequently neglected because it is typically much smaller than the other coefficients, and is therefore not shown above.)

Many manufacturers provide application notes (e.g. here) detailing on how to calibrate a given NTC if you desire accuracy better than the quoted manufacturing tolerance.

The provided B-coefficient can be used in a simplified Steinhart-Hart equation as described on the Wikipedia Thermistor article under "B parameter equation".