Thermistor (thermoresistor) is a semiconductor resistor, which electrical resistance considerably depends on temperature. It is used for registration, temperature measurement in thermal control systems, in power meters and other devices.
There are two thermoresistor types: PTC (positive temperature coefficient) and NTC (negative temperature coefficient). The resistance of PTC thermistor, when the temperature is rising, increases, but in case of NTC thermistor – decreases.
Thermistors have high resolution and accuracy of ± 0,001°C with a good calibration. They are highly sensitive, have a simple two-wire connection circuit (which doesn’t require temperature compensation of free ends comparing to a thermocouple), a relatively high speed. But at the same time they have some disadvantages: a sharply nonlinear transformation characteristic and poor characteristic repeatability. In addition, they have a relatively narrow temperature range under measurement.
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