Thermometer Principle

Understanding the working principle, technical indicators, environmental working conditions, operation and maintenance of infrared thermometers is the basis for users to choose and use infrared thermometers correctly. The optical system collects the target infrared radiation energy in its field of view, and the size of the field of view is determined by the optical parts and position of the thermometer. Infrared energy is focused on the photoelectric detector and converted into corresponding electrical signals. The signal is converted into the temperature value of the measured target after being corrected by the amplifier and the signal processing circuit according to the internal algorithm of the instrument and the target emissivity. In addition, the environmental conditions of the target and the thermometer, such as temperature, atmosphere, pollution and interference, etc., should also be considered to affect the performance index and correction methods.

All objects with a temperature above absolute zero are constantly emitting infrared radiation energy into the surrounding space. The size of the infrared radiation energy of an object and its distribution according to wavelength are closely related to its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, it can accurately determine its surface temperature, which is the objective basis on which infrared radiation temperature measurement is based.

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

The effect of the emissivity of an object on the temperature measurement of radiation: practical objects existing in nature are hardly black bodies. In addition to the radiation wavelength and the temperature of the object, the radiation amount of all actual objects is also related to the types of materials that constitute the object, the preparation method, the thermal process, and the surface state and environmental conditions. Therefore, in order to apply the law of blackbody radiation to all real objects, a proportionality factor related to the material properties and surface state must be introduced, namely the emissivity. This coefficient indicates how close the thermal radiation of an actual object is to black body radiation, and its value is between zero and a value less than one. According to the law of radiation, as long as the emissivity of a material is known, the infrared radiation characteristics of any object are known