Thermistors, derived from the term thermally sensitive resistors, are a very accurate and cost effective method for measuring temperature. Thermistors are usually two-terminal semiconductor devices made from semi-conductor materials that have an electrical resistance that varies non-linearly with temperature. Some materials provide better stability while others have higher resistance ranges and are fabricated into smaller thermistors. Each specificthermistor has its own unique resistance versus temperature characteristic. 

Often during the rebuild and overhaul of a piece of electrical apparatus, we are faced with the challenge to identify the type of temperature detection devices that need to be replaced.Types of temperature detectors discussed include: Resistance Temperature Detectors (RTDs) Thermocouples Thermistors Thermostats

When we mention temperature detectors for motors we usually think of winding temperature detectors. However, temperature detectors can also be used to monitor bearings and airflow. In this article we will describe the more common types of temperature detectors and how they can be applied to windings, bearings and to check ventilation (airflow).