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  • Thermocouple is extensively used in steel processing, turbine and diesel engine for temperature measurement
  • It is used in gas feed heat appliances such as ovens and water heaters.
  • It is used in power production.
  • A thermocouple can be used as a vacuum gauge over the range of approximately 0.001 to 1 torr absolute pressure
  • Thermoelectric cooling
  • Medical equipment and Packaging equipment 

2.Thermistor:

A thermistor is type of resistor whose resistance varies significantly with the temperature. They are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors and self-regulating protectors.

It is cheap and easily abundant temperature sensors which is easy to use and adaptable also. Circuits with thermistor can have reasonable output voltages- not the millivolt output as thermocouples have. Because of these qualities they are widely used for simple temperature measurements but not for the high one. But in the temperature ranges where they work are widely used.Image Added

 

How Does A Thermistor's Resistance Depend Upon Temperature?

Steinhart-Hart equation gives the reciprocal of absolute temperature as a function of the resistance of a thermistor.

Using the Steinhardt-Hart equation, you can calculate the temperature of the thermistor from the measured resistance.

The Steinhardt-Hart equation is:

1/T = A + B*ln(R) + C*(ln(R))3 R in W, T in oK

The constants, A, B and C can be determined from experimental measurements of resistance, or they can be calculated from tabular data.

How Do You Use A Thermistor?

In this bridge circuit, three resistors are constant, Ra, Rb, and Rc, while the resistive sensor, Rs, varies depending upon some physical variable - like temperature, light level, etc.  That's where the thermistor can be used.

        The thermistor can be placed anywhere in the bridge with three constant resistors, but different placements can produce different behaviour in the bridge.  For example, different placements might cause the output voltage to go in different directions as the temperature changes.

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References:

  1. 1.      http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/TempR.html
  2. http://en.wikipedia.org/wiki/Thermistor

 

 

 

references:

http://www.electronics-tutorials.ws/io/io_3.html

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