Explain about Thermistors?

A thermistor is a resistive device composed of metal oxides formed into a bead and encapsulated in epoxy or glass. A typical thermistor shows a large negative temperature coefficient. Resistance drops dramatically and non-linearly with temperature.

Sensitivity is many times that of RTDs but useful temperature range is limited. There are wide variations of performance and price between thermistors from different sources.

Typical benefits are:

• Low sensor cost: Basic thermistors are quite inexpensive. However, models with tighter interchangeability or extended temperature ranges often cost more than RTDs.

• High sensitivity: A thermistor may change resistance by tens of ohms per degree temperature change, versus a fraction of an ohm for RTDs.

• Point sensing: A thermistor bead can be made the size of a pin head for small area sensing.