A Thermistor has a series of resistors whose values are changed by the temperature changes around them. These value changes affect a current that is generated either by the recording system into which they are plugged or by inline batteries.

A thermocouple comprises two wires made from dissimilar metals. A temperature change at the junction of these two metals will generate an electrical signal because of their metallurgical properties. This is accomplished using specific metals. Different metals are used to measure different temperature ranges resulting in different Types of thermocouples.