Thermistors

Thermistors are among the most accurate temperature-sensing components available. They are resistive devices whose resistance changes significantly with temperature, making them suitable for applications such as temperature sensing, inrush current limiting, self-resetting overcurrent protection, and self-regulating heating elements.

Thermistors are classified based on the sign of k, the first-order temperature coefficient of resistance. When k is positive, resistance increases as temperature rises; these devices are known as Positive Temperature Coefficient (PTC) thermistors, or posistors. When 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 widely used in applications including digital thermostats, battery packs, televisions, and automotive systems. In particular, NTC thermistors are commonly used to measure coolant and oil temperatures in vehicles.

NTC thermistors are defined by parameters such as their nominal resistance at a reference temperature—typically 25 °C—and their B value, which describes the temperature-to-resistance relationship over a specified range. These characteristics make NTC thermistors especially well suited for precise temperature measurement and control applications.