Which device is a thermistor?

• A. Thermostat
• B. RTD
• C. Thermocouple
• D. Thermistor

Answer: (D)

A thermistor is a temperature-sensitive resistor—its resistance changes with temperature. This large, often nonlinear resistance change is what makes it useful as a temperature sensor or for temperature compensation. While another device, an RTD, also changes resistance with temperature, it uses a metal element (like platinum) for higher accuracy and linearity, and isn’t called a thermistor. A thermocouple generates a voltage based on temperature difference between two metals, not a change in resistance. A thermostat acts as a switch to control heating or cooling, typically using a bimetal element, not a resistance that varies with temperature. So the device that fits the definition of a thermistor is the thermistor itself.