Temperature measurement emissivity of infrared thermometer
A black body is an idealized radiator that absorbs radiant energy of all wavelengths, has no reflection or transmission of energy, and has an emissivity of 1 on its surface. However, the actual objects in nature are almost not black bodies. In order to clarify and obtain the distribution law of infrared radiation, an appropriate model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, thus Derived the law of Planck's black body radiation, that is, the black body spectral radiance expressed by wavelength, which is the starting point of all infrared radiation theories, so it is called the law of black body radiation. The radiation amount of all actual objects depends not only on the radiation wavelength and the temperature of the object, but also on the type of material constituting the object, preparation method, thermal process, surface state and environmental conditions. Therefore, in order to make the law of black body radiation applicable to all practical objects, a proportional coefficient related to material properties and surface states must be introduced, that is, emissivity. This coefficient represents how close the thermal radiation of an actual object is to the radiation of a black body, and its value is between zero and a value less than 1. According to the law of radiation, as long as the emissivity of the material is known, the infrared radiation characteristics of any object are known. The main factors affecting emissivity are: material type, surface roughness, physical and chemical structure, and material thickness. When measuring human body temperature, the emissivity is generally adjusted at 0.95 to measure the most accurate temperature.
Human body infrared thermometer
Infrared thermometers used to test the temperature of the human body are called human infrared thermometers. But it must be clarified that there is no special medical or industrial infrared thermometer, because the manufacturing principles of infrared thermometers are the same. There are only high-precision, high distance coefficient ratio, high-performance infrared thermometers and low-precision, low distance coefficient ratio and low-performance infrared thermometers. As long as the emissivity of the infrared thermometer is set at 0.95 (the emissivity of human skin is generally this value, even if there is a difference, the impact is only within 0.3 degrees), it meets the requirements of human body temperature measurement. (For example: all brands of cars can run at a speed of 40 yards, and high-end cars may reach a speed of 200 yards, but there is no distinction between cars that specialize in running 40 yards and cars that specialize in running 200 yards, only the difference between high and low performance cars .)
