Thermally Sensitive Resistors / Thermistors

Thermally Sensitive Resistors

Rg Allen thermistors

Thermistors are thermally sensitive resistors whose prime function is to exhibit a large, predictable and precise change in electrical resistance when subjected to a corresponding change in body temperature. Negative Temperature Coefficient (NTC) thermistors exhibit a decrease in electrical resistance when subjected to an increase in body temperature and Positive Temperature Coefficient (PTC) thermistors exhibit an increase in electrical resistance when subjected to an increase in body temperature.

A thermistor is an element with an electrical resistance that changes in response to temperature. This name is derived from the more descriptive term "thermally sensitive resistor," the original name for these devices. Thermistors were first discovered by Michael Faraday in 1833, although commercially useful thermistors weren't manufactured until 1930. They're now widely used in a variety of electronic applications, most often as temperature sensors. Additional uses of thermistors include current limiters, current protectors and heating elements.

A thermistor's change in electrical resistance due to a corresponding temperature change is evident whether the thermistor's body temperature is changed as a result of conduction or radiation from the surrounding environment or due to "self heating" brought about by power dissipation within the device.

Thermistors are one of the most accurate types of temperature sensors. They are resistors whose resistance varies greatly with temperature. This resistor type is used commonly as an inrush current limiter, temperature sensor, self-resetting overcurrent protector, and self-regulating heating element. The two types of Thermistors are based on the sign of k, which represents the first-order temperature coefficient of resistance. If the k is positive, resistance increases with temperature increase and the device is referred to as a positive temperature coefficient (PTC) Thermistor, or posistor. If k is negative, resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) Thermistor. Both PTC and NTC Thermistors are used in a wide range of applications, including measuring coolant and oil temperatures in automobiles (NTC thermistors), digital thermostats, battery packs, and televisions.


Industries Served



Medical
Thin film thermistors featuring ultra-miniature size, excellent response time and high-accuracy, make temperature sensing possible within the most stringent physical limitations. Highly recommended for various types of catheter applications.

Automotive
Thermistors can be found across a broad range of automotive applications including battery, motor, inverter, HVAC and ECU temperature management.

Office Automation
Thermistors are being used across the globe in office equipment including printers and copiers. Our contact and non-contact sensors for example, are critical components essential for temperature management of laser printer fuser assemblies.

Home Appliances
Thermistors can also be found in a wide variety of home appliances ranging from HVAC equipment, microwave ovens, gas stoves/ranges, refrigerators to water heaters.

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