Types of Pyrometers and Working Principle and Advantages

A pyrometer is a thermometer that measures temperatures from a distance. It is used in many industries to measure the temperature of an object or material without making contact with it. Pyrometers are used in industrial processes, such as steelmaking and glassmaking, to measure the temperature of molten metals or hot glass. 

Such instruments which are made for measuring high temperatures are called Pyrometer, they are mainly of two types.

1. Optical Pyrometer 

An optical Pyrometer is widely used to accurately measure the temperature of molten metals and other hot substances in a furnace. These are often used for the range from 1000 to 5000°F.

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Construction And Working

It consists of an objective lens and after that, a bulb is attached. The filament of the bulb acts as a radiation source, after the bulb, there is a red filter and eyepiece. To heat the filament in the bulb, a battery current controller and an object in its series make the real image of the object on the filament. In the background of this image, the filament is viewed through the red filter through the eyepiece.

If the value of current flowing through the filament is less then the filament appears black relative to the image. If the value of the current flowing in the filament is high, then the glow appears.

The current in the filament is controlled so that the brightness of the image of the filament and the object becomes equal. This value of the wind is determined by the ammeter. The temperature of the filament can be calculated from i = a + bt +at.

2. Radiation Pyrometer 

This instrument is made or made to measure very high temperatures, in these instruments heat is measured by radiation, these instruments are called radiation pyrometers.

Construction And Working

With a pyrometer, we collect the hot radiation coming from a substance with the help of a concave mirror on a calico plate whose back surface is in contact with the measuring function of the thermocouple, due to which the radiation on it increases the temperature. 

And e.m.f is generated in the circuit, read from the M.V. connected to the circuit. In this calculation of hot substance can be used.

Advantages 

The main advantage of this thermometer is that the heated substance does not have to be kept in contact with it, so there is no definite limit to the temperature range. 

It can measure temperatures from 800°C to 3000°C to 4000 °C.

Disadvantage

This instrument cannot be used to measure temperatures below 800°C because the interference emission at these temperatures is so low that its accurate measurement is not possible.

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