Black Body is the most ideal calibrator of an infrared thermometer. This is because blackbodies have an Emissivity equal to 1.000.

A perfect blackbody only would have an emissivity of 1.000. This would take place in a system where no light or radiation could escape and all the radiation shall remain inside forever. In the real world, there is no such thing as a perfect blackbody for IR thermometry. This is because there would be no opening for taking a measurement in such a system. However, the perfect blackbody is a good prototype for modeling thermal radiation.

Emissivity is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an emissivity = 1 while any real object would have emissivity < 1. Emissivity is a dimensionless quantity. Every material radiates energy. The amount of radiated power is dependent on the material’s temperature and the material’s emissivity.

IR thermometers make use of this. They measure the amount of energy radiated by an object in an infrared band. This infrared band can vary from 1 micro meter to 14 micro meters. Depending on the wavelength range IR thermometers uses different types of sensors to determine the temperature. They calculate temperature based on this measured power and the material’s emissivity.

Emissivity is one of the major sources of error in infrared measurements. Knowledge of the emissivity of the measured surface is of great value to any user of an IR thermometer. As so, great care should be taken to know the effects of emissivity of the surface when measuring it. Deviation in the assumed emissivity of the measuring target body would lead to significant error in temperature measurement. Proper knowledge of emissivity and background temperature should be considered when measuring a surface temperature. These factors are even more important when using an IR thermometer calibrator. Paying attention to these factors will provide a better calibration and better IR metrology.