Measuring temperature using thermistors: The Steinhart-Hart coefficients

The thermistor is a useful device for measuring temperature in certain situations. ( See the earlier post in this blog).The issue is that the thermistor has a non linear temperature response and thus may be complicated in use if used directly. The thermistor curve (temperature versus resistance ) has been modeled very accurately by an analytical equation which can be used to advantage in thermistor based temperature measuring circuits. The fixed coefficients in this equation are referred to as the Steinhart-Hart coefficients and can be either obtained from the manufacturer of the thermistor or be extracted from a resistance versus temperature curve. In any case, once these coefficients are known, an analog – digital system of circuits can be used with a microprocessor, to measure temperature relatively accurately. A paper on the extraction of the coefficients and the analytical approach has been released by Signal Processing Group Inc., and is available for interested readers at>engineer’s corner.

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