(EI&C Engineering Department)

By:-By:-Ritu Sharma(12EEAEI047)Ritu Sharma(12EEAEI047)Preeti Mahour(12EEAEI040)Preeti Mahour(12EEAEI040)

Government Engineering College, Ajmer

A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots. It produces a voltage when the temperature of one of the spots differs from the reference temperature at other parts of the circuit. 

The Seebeck effect is the conversion of thermal energy/temperature differences directly into electrical energy or electricity.

This effect measures the ease at which excess electrons will circulate in an electrical circuit under the influence of thermal difference.

The change in the voltage is proportional to the temperature difference between the junctions when the ends are connected to form a loop.

Ice-pointThe result of the calibration is a table of EMF versus T values. The integral is never directly evaluated. Instead a polynomial curve fit to the calibration data gives:

njnjjjj TbTbTbbTFE .....2

2100

With reference to the characteristics of pure Platinum

emf

Temperature

Types T, J, and K are most commonly used thermocouples (see Table 16.8 of the “Handbook”).

1.Steel industry2.Gas appliance safety3.Thermopile radiation sensors4.Manufacturing 5.Power production6.Thermoelectric cooling7.Process plants8.Thermocouple as vacuum gauge

It is rugged in construction Covers a wide range of

temperature Comparatively cheaper in cost Calibration can be easily checked Offers good reproducibility High speed of response Satisfactory measurement

accuracy

For accurate temperature measurements, cold junction compensation is necessary

The emf induced versus temperature characteristics is somewhat non-linear

Stray voltage pickup is possible In many applications, amplification of

signal is required