what is a thermistor

A thermistor is a type of resistor whose resistance changes with temperature. It is a semiconductor device that is made of metallic oxides, pressed into a bead, disk, or cylindrical shape and then encapsulated with an impermeable material such as epoxy or glass. Thermistors are categorized based on their conduction models. Negative-temperature-coefficient (NTC) thermistors have less resistance at higher temperatures, while positive-temperature-coefficient (PTC) thermistors have more resistance at higher temperatures. Thermistors are used in many applications including household appliances, water tanks, pipes, and equipment casings. They are highly accurate but only over a limited temperature range that is within about 50°C of a base temperature. Thermistors are often selected for applications where ruggedness, reliability, and stability are important. They are best used when a specific temperature needs to be maintained, and when monitoring temperatures within 50°C of ambient.