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Thermocouple [ Model : TE ]
What is thermocouple?
When two dissimilar metal conductors are connected together to form a closed circuit and the two junctions are kept in different temperatures, thermal electromotive force (EMF) is generated in the circuit.
Thus, when one end (cold junction) is kept constant at a certain temperature, normally at 0oC, and the other end (measuring junction) is exposed to unknown temperature, the temperature at latter end can be determined
by measurement of EMF so generated. This combination of two dissimilar metal conductors are called "Thermocouple".
Features of ThermocoupleThus, when one end (cold junction) is kept constant at a certain temperature, normally at 0oC, and the other end (measuring junction) is exposed to unknown temperature, the temperature at latter end can be determined
by measurement of EMF so generated. This combination of two dissimilar metal conductors are called "Thermocouple".
Industrial thermocouple, in comparison with other thermometers, have the following features.
- Quick response and comparatively small time-lag
- If appropriate selection of a quality thermocouple is made, wide range of temperature from absolute 0 to 2,300oC can be measured
- Temperature of specific spot or small space can be measured
- Since temperature is detected by means of EMF, measurement, adjustment, amplification, control, conversation and other data processings are easy
- Less expensive and easily available in comparison with other temperature sensors
Structure and Measuring Method
Generally, industrial thermocouple is inserted into an insulating tube to prevent short circuit between the element wires and then inserted into a protective tube so as not to contact directly the object or surrounding atmosphere. Reference junction is compensated at a certain temperature (mostly at 0oC) for measurement. The EMF so generated is measured by means of moving coil type, electronic type, auto-balancing type, potentiometric or other indicating instruments.
recautions in Practical Applications
Since there are various types of thermocouples, it is most important to select the appropriate thermocouple for the specific application. In addition, care should be given to the selection of protection tube, structure and fitting method with due consideration of resistance to heat, corrosion and vibration.
