The word 'pyrometer' is derived from the Greek words 'pyro', meaning fire and 'meter', which in order to measure. Hence, by cumulative definition as by function, a pyrometer is a device to measure top temperature of an item. It is a gun shaped instrument in which detect temperature by non-contact methods. This can include irradiance, emissivity and infrared radiation. All pyrometers essentially follow the Stefan-Boltzmann law for temperature detection and calculation. They can typically measure temperatures in the array of 100 to 1999 F. The first pyrometer was invented along with a potter to study the temperature of his kiln. Development of this Brightness Pyrometer and also the Ratio Pyrometer then followed. Today important types of pyrometers in use are Optical Pyrometers, Resistance Pyrometers and Radiation Pyrometers. An optical pyrometer is constructed a great optical system along with detector. Every heated object undergoes a difference in colour and brightness and emits small amounts of radiation, about 3.4 to 0.7 microns. The optical pyrometer determines the temperature of the hot object by using colour matching. Another variation of the optical pyrometer is determining temperature of the filament by varying strength of current to match the shade of the detector filament with one particular being measured. Optical pyrometers require temperature calibration. A resistance pyrometer (RTD) determines temperature by measuring the change in resistance belonging to the heated materials electric energy. This type of pyrometer is applied when the object of temperature measurement cannot be created. These pyrometers require RTD calibration every couple of years or every may function too agressively. Radiation pyrometers make use of the concept of infrared radiation for temperature measurement. The pyrometer senses, records and compares the temperature of an object from the radiation it gives absent from. Heat-sensitive elements such as a thermocouple, a device that produces an energy current when part of it is heated, are used. The present generated in the thermocouple due towards heated object operates a dial that indicates temperature. Periodic thermocouple calibration is called for to maintain the precision of these pyrometers. Different varieties of pyrometers are being used for different temperatures and submissions. The optical systems also vary accordingly. Pyrometers find applications numerous industries but are primarily raised for electrical research. They help read the heating on power meters making sure that the electrician or handler is protected from burns. This tool allows the person to avoid any contact whatsoever while object being measured.