Thermistor

A THERMISTOR is a temperature-sensitive resistor -- its electrical resistance changes as its temperature changes. There are two types. An NTC (Negative Temperature Coefficient) thermistor's resistance DECREASES as its temperature increases, giving it a negative temperature coefficient; NTC thermistors are commonly used as temperature sensors and in temperature-control circuits. A PTC (Positive Temperature Coefficient) thermistor's resistance INCREASES as its temperature increases instead; PTC thermistors are commonly connected in series within a circuit and used as a reusable, resettable fuse, limiting the current through the circuit to protect it against over-current conditions.

Thermistors are made from thermally sensitive metal-oxide semiconductor materials, and they are highly sensitive: even a small change in the surrounding temperature produces a comparatively large change in their resistance. Because they can also be made physically very small, they are well suited to measuring temperature variation within a small, localised area. Both NTC and PTC thermistors find wide application across industry. …