Introduction Thermocouples are the most widely used device for measuring and sensing temperature in which two wires (conductors) of distinct similarity are joined with their free ends (of the wires) linked to an instrument that measures the difference in potential at the junction (of the ends) of the conductors. The discovery of thermocouple is traced back to a German physicist Thomas Seebeck who in 1821 discovered that voltages exist between the two ends of a conductor, in which case metals at different temperature where used. His work revealed that voltages at the ends where proportional to the changes in the temperature difference of the two conductors. Modern theories studying the behavior of electrons within a material’s molecular structure provide an analytical explanation to back Seebeck phenomena. However should be noted that the magnitude of voltages produced at the junction of the two conductors, depends on the type of conductions used and the magnitude of voltage produced is usually in millivolt. Basic Principle Of Operation It has been observed that when one end of a conductive material is heated to a temperature higher than the opposite end, the electrons at the hotter end become more thermally energized than the electrons at the relatively cooler end. As a result these thermally energized electrons begin to diffuse towards the cooler end. This redistribution of electrons creates negative charges at the cool end and an opposite but equal positive charge at the hot end, thus maintaining charge neutrality. Hence heating on end of a conductor consequently creates an electrostatic voltage caused by redistribution of elections throughout the entire material. This effect is known as Seebeck effect and is the basic principle of thermocouples. Applications Of Thermocouples
The magnitude of voltage produced by thermocouple is proportional to the difference in the temperatures of the two conductors used in producing the thermocouple. The magnitude of voltage is dependent on the type of metals used in the production of the thermocouple. It has vast applications which include: fail safe for gas safety appliance such as oven and heaters, production of vacuum gauges, measurements of irradiation and so on. It has found vast application both in home and industries because its market cost is quiet low compared to other temperature sensing devices and its market availability is relatively high.
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February 2019
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