What is pyrometer? Explain any one type of pyrometer.
1 Answer
Answer :
Pyrometers: Pyrometers is an instrument used for measuring temperature without any physical contact. It depends upon the relationship between the temperature of a hot body and the electromagnetic radiation emitted by the body. When a body is heated, it emits thermal energy known as heat radiation. A black matt surface (or a black body) is a very goodabsorber of heat radiation and, also, a very good emitter of such radiations whenheated. Pyrometry is a technique for determining a body’s temperature by measuringits electromagnetic radiation.
Types: 1. Optical pyrometers 2 . Radiation Pyrometers
Optical pyrometers:
The working principle of optical pyrometer state that the brightness of light of a given color emitted by a hot source, gives an indication of temperature. During the operation of optical pyrometer following conditions occurs.
1. When the temperature of the filament is higher than that required for equal brightness then the filament is too bright as shown in the figure.
2. When the temperature of filament is lower, the filament becomes too dark as shown in fig.
3. When the brightness of image produced by the source and brightness produced by the filament are equal, the outline of the filament disappears as shown in fig.
(OR)
Radiation Pyrometers: Construction of radiation pyrometers, which consist of blackened tube. One end is exposed to the hot body whose temperature is to be measured, at the other end of the tube sighting aperture is present, is which an adjustable eye piece is fitted. i) One concave mirror is provided as shown in figure to collect the radiations coming from the body whose temperature is to be measured. ii) The position of concave mirror is adjusted using rack and pinion so as to get proper focusing of thermal radiation on the detector disc. The detector disc consists of blackened platinum sheet or foil. iii) The output of detector is given to the meter for measuring the thermoelectric EMF or resistance which is a direct indication of temperature of hot body.