typical applications of different types of pyrometers.
The word pyrometer originated from the Greek word, fire, "πυρ" (pyro), and meter, meaning to measure. Pyrometry is the science of measuring temperature greater than 1500 degree Celsius and therefore Pyrometer is the instrument that is used to generally measure high temperatures. [dictionary] They usually measure the temperature of the surface of the object. The surface of the object emits radiation which is used as a measurement for pyrometers. Due to the high temperature conditions, the measurement uses an indirect temperature technique. Instruments for temperature measurement by radiation are called radiation thermometers. The four principal techniques for the measurement of temperature by radiation are; 1. Total radiation
2. Pyroelectric thermometers
3. Optical disappearing filament thermometers
4. Photoelectric radiation pyrometers
Assembly and Operational Principal
Using this type of instrument, the radiation emitted by the body in which the temperature is required is directed on a thermal receiving element. The receiving element comes in a variety of forms which would include a thermocouple or a thermopile or a resistance element which usually comes in a form of a thin strip of blackened platinum. In a radiation thermopile, a large number of thermocouple in the form of fine strips are arranged circularly to make a wheel so that all the hot junctions will fall within a very small target area. These strips are blackened to increase the energy absorbing ability.
The hot junctions are rarely above a few hundred degrees Celsius and that makes it very stable. The thermocouple are also not exposed to the contaminated surrounding of the furnace.
Advantage and Disadvantage.
Having the thermopile as a detector produces a measurable e.m.f which acts as an advantage. As mentioned above, the hot junctions of the thermopile makes it a stable instrument of...
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