Influence of emissivity of thermometer object on radiation temperature measurement
The actual objects that exist in nature are almost not black bodies. 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, the preparation method, the thermal process, the surface state and the 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 indicates how close the thermal radiation of the actual object is to the black body radiation, 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 can be known.
The main factors affecting the emissivity of infrared thermometers are:
Material type, surface roughness, physical and chemical structure and material thickness, etc.
When using an infrared radiation thermometer to measure the temperature of a target, it is first necessary to measure the infrared radiation of the target within its band range, and then the temperature of the measured target is calculated by the thermometer. Monochromatic pyrometers are proportional to the amount of radiation in a band: dual-color pyrometers are proportional to the ratio of the amount of radiation in the two bands.
The infrared thermometer must correctly correspond to the selection of the infrared system:
The infrared thermometer is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system gathers the infrared radiation energy of the target in its field of view, and the size of the field of view is determined by the optical parts of the thermometer and its position. Infrared energy is focused on a photodetector and converted into a corresponding electrical signal. The signal passes through the amplifier and the signal processing circuit, and is converted into the temperature value of the measured target after being corrected according to the algorithm of the internal treatment of the instrument and the emissivity of the target.
The selection of infrared thermometer can be divided into three aspects:
Performance indicators, such as temperature range, spot size, working wavelength, measurement accuracy, response time, etc.; environmental and working conditions, such as ambient temperature, window, display and output, protection accessories, etc.; other options, such as ease of use, maintenance And calibration performance and price, etc., also have a certain impact on the choice of thermometer. With the continuous development of technology and technology, the best design and new progress of infrared thermometers provide users with various functions and multi-purpose instruments, expanding the choice.
