Chapter 2 ExerciseThermistor

Also called thermal resistor as the resistance varies as a function of temperature.

Manufactured in the form of beads, discs and rods.

Most thermistors have a negative coefficient (NTC) of temperature resistance.

Three important characteristics:o Resistance – Temperatureo Voltage – Currento Current – Time

Thermistor

Thermistor

Major applications of thermistors are measurement and control of temperature.

Other applications of thermistors:o Measurement of power at high frequencies.o Measurement of thermal conductivity.o Measurement of level, flow and pressure of liquids.o Measurement of composition of gases. Vacuum measurement.

Thermistor

Advantages

o High sensitivity especially in NTC region.o Fast response over narrow temperature range.o Cold junction compensation is not required.o No problems on contact and lead resistance.o Low cost and small size.

Limitations

o Characteristics of resistance are non-linear.o Not recommended for wide temperature range application.o Need a shielded power lines or filters and low excitation current.

Thermistor

Thermistor – Exercise Question

Thermistor – Exercise Question

Thermistor –Exercise Question