What is Pyrometer ?

:- Temperature above 150° C are measured by instruments known as pyrometers . A Pyrometer is a type of thermometer used to measure high temperature. It is used for measuring Temperature without any physical contact . It is used for measuring body temperature by measuring it’s electromagnetic radiation.

Types of pyrometers :

Pyrometers commonly employed in engineering practic are :

1. Thermo-electric Pyrometer.

2. Radiation Pyrometer.

3. Optical Pyrometer.

4. Pyrometric cone Pyrometer.

Explanation :

1.Thermo-Electric Pyrometer:

It is used for measuring Temperature from 150° to 1,600°C. It consists of a thermo-couple, an indicating or recording device and suitable connecting wires. When one end of a thermo-couple is heated an electromotive force is generated which is applied either to a mili-voltmeter or potentiometer which is calibrated to read in degrees. The magnitude of electromotive force developed depends upon the temperature difference of the hot junction and cold junctions.

 2. Radiation Pyrometer:

It is used for measuring temperature above 550°C. This instrument utilizes the heating effect of energy radiated from a hot object as an index of it’s temperature.

It consists of four essential elements, namely :

1. Cylindrical tube containing a concave mirror

2. Lens focused on the hot object

3. Small thermo-couple on which mirror concentrates it’s rays

4. Measuring device which is the same as that used with thermo-couple.

3. Optical Pyrometer:

This is an instrument which is suitable only for high temperature work. The hot body is viewed through a telescope. A small electric filament lamp is arranged inside this telescope, so that the image of the filament is superimposed on that of the variation of hot body. A variable resistance arranged in filament circuit enables to vary the temperature of the filament. This resistance is adjusted so that the image of the filament merges or disappears into the image of the hot body. Under these conditions these temperatures are similar. So, resistance Control can be calibrated in terms of temperatures.

 4. Pyrometric cone Pyrometer:

It is used for measuring the furnace temperature. It can be used for temperature from 600°C to 2,000°C.

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Bapi Sarkar.