16-03-2012, 12:26 PM
Temperature Sensors
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Plane of my seminars
Types of Temperature Sensors
Working
Applications
Summary
It is a sensor which relies the physical principle that any two different metals A and B are connected together, an emf that is a function of the temperature will be developed at the junction of these metals.
E=a1t+a2t2+a3t3+…….
Therefore the temperature and emf relationship is non linear
a1,a2,a3,a4……….depends upon the metals
Principle of working
Thomson effect: When two decimal metals are joined together an emf exist between the two points that is function of the junction temperature
Feltier effect: If two metals are connected to an external circuit in such way that current is drawn, the emf may be altered
Thomson effect: If a temperature gradient exists along either or both of the metals the emf may under go an additional modification
Two important laws
1.Solving the problems of thermocouple
In this intermediate metals and intermediate temperature are important
Law of intermediate metals
2.If a thermocouple produces circuit e1when the junction are at the temperatures t1 and t2 and e2,when at temperature t2 and t3 then it will produce an emf (e1+e2),if the junctions are at metals temperatures t1 and t3
Law of intermediate temperature
