What is Thermistors means?

Thermistor is a means of a term "Thermal Resisters".Thermistors are generally made from Semi-Conductor Materials.Most Thermistors have Negative Coefficient of Temperature Resistance i.e.Their Resistance decrease with increase in Temperature.

The Negative Temperature Coefficient of Resistance can be large as several percent per Degree Celsius.This allows the Thermistor Circuits to detect very small changes in Temperature which could not be observed with a Thermocouple.

Thermistors are widely used in applications which involves Measurements in the range of minus 60 degree Centigrade to 15 degree Centigrade.The Resistance of Thermistors ranges from 0.5 ohms to 0.75 mega ohms.
Thermistor is highly sensitive device.the Thermistor exhibits a highly Non Linear characteristics of Resistance versus Temperature.

Construction of Thermistors:-

Thermistors are composed of sintered mixture of Metallic oxides such as Manganese,Nickel,Cobalt,Copper,Iron and Urenium.They are available in variety of sizes and shapes.The Thermistors may be in the form of beads,rods and discs.

A Thermistor in the form of beads is smallest in size and bead may have a Diameter of 0.015 mm to 1.25 mm.(Beads may be sealed in the tips of Solid Glass Rod to form Probes which may be easier to mount than the beads).

Glass Probe have a Diameter of about 2.5 mm and a length which varies from 6 mm to 50 mm.Discs are made by pressing material under high pressure into Cylindrical Flat Shape with Diameters ranging from 2.5 mm to 25 mm.

The three important characteristics of Thermistor make them extremely useful in Measurement and Control Applications,these are as follows.

01)The Resistance:-Temperature characteristics

02)The Voltage:-Current characteristics

03)The Current:-Time characteristics

Applications of Thermistors.

Major Applications of Thermistors are Measurement and Control of Temperature they may be used for number of other applications.

01)Measurement of Temperature.

02)Control of Temperature.

03)Temperature Compensation.

The other Applications of Thermistors includes,

01)Measurement of Power at High Frequencies.

02)Measurement of Thermal Conductivity.

03)Measurement of Level,Flow and Pressure of Liquids.

04)Measurement of Composition of Gases.

05)Vacuum Measurement.

06)Providing Time Delay.