Understanding the working principle, technical specifications, environmental working conditions, operation, and maintenance of infrared thermometers is the foundation for users to correctly choose and use them. The optical system collects the infrared radiation energy of the target within its field of view, and the size of the field of view is determined by the optical components and position of the thermometer. Infrared energy is focused on the photodetector and converted into corresponding electrical signals. The signal is converted into the temperature value of the measured target after being amplified and processed by the signal processing circuit according to the algorithm and target emissivity correction inside the instrument. In addition, the environmental conditions of the target and thermometer, such as temperature, atmosphere, pollution, and interference, should also be considered for their impact on performance indicators and correction methods.

All objects with temperatures above absolute zero are constantly emitting infrared radiation energy into the surrounding space. The magnitude and wavelength distribution of infrared radiation energy of an object are closely related to its surface temperature. Therefore, by measuring the infrared energy radiated by an object itself, its surface temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.

Blackbody radiation law: A blackbody is an idealized radiation body that absorbs radiation energy of all wavelengths without reflection or transmission of energy, and its surface emissivity is 1. It should be pointed out that there is no true blackbody in nature, but in order to clarify and obtain the distribution law of infrared radiation, a suitable model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, which derived Planck's law of blackbody radiation, namely the spectral radiance of blackbody radiation expressed in wavelength. This is the starting point of all infrared radiation theories, hence it is called the blackbody radiation law.