Thermistor Definition Construction and ApplicationsPublished on 24/2/2012 and last updated on 24/8/2018
Construction of ThermistorThere are different shapes and sizes of thermistors available in the market. Smaller thermistors are in the form of beads of diameter from 0.15 millimeters to 1.5 millimeters. Thermistors may be in the form of disks and washers made by pressing thermistor material under high pressure into flat cylindrical shapes with diameter from 3 millimeters to 25 millimeters.
Characteristics of ThermistorsThe relationship governing the characteristics of thermistors is given below as: R1 = resistance of thermistor at absolute temperature; T1oK. R2 = resistance of thermistor at temperature T2oK. β = constant depending upon material of transducer. From the above equation, we can conclude that the relationship between temperature and resistance is highly nonlinear. A thermistor usually exhibits a negative thermal resistance temperature coefficient of about 0.05 / oC.
Applications of ThermistorsThermistors are used for the measurement of temperature as a change of temperature produces a large change in their resistance. They are used for the control of the temperature in any circuit.
Thermal Compensation - They can be used for the temperature compensation in any circuit. For example in any circuit a simple carbon resistor is connected which has a positive thermal coefficient. So, if the resistance of carbon resistor is to be made unaffected by the temperature so a thermistor having same negative thermal coefficient is connected in series with it. So, as due to rising in temperature resistance of resistor increases and resistance of the thermistor decreases by the same amount as the magnitude of there thermal coefficients is same. So, as the resistor and thermistor are in series, thus the net resistance of resistance remains the same. We use thermistor also for measurement of thermal conductivity of electrical materials.