Effect of object emissivity on pyrometer temperature measurement
Almost all actual objects that exist in nature are not black bodies. The amount of radiation emitted by all real objects depends, in addition to the wavelength of the radiation and the temperature of the object, on such factors as the type of material constituting the object, the method of preparation, the thermal process and the state of the surface and environmental conditions. Therefore, in order for the blackbody radiation law to apply to all real objects, a proportionality coefficient, i.e., the emissivity, related to the nature of the material and the state of the surface, must be introduced. This coefficient represents the proximity of the thermal radiation of a real object to the blackbody radiation, and its value ranges 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.
The main factors affecting emissivity are: material type, surface roughness, physical and chemical structure and material thickness.
When using infrared radiation thermometer to measure the temperature of the target first to measure the target in its band range of infrared radiation, and then by the thermometer to calculate the temperature of the target to be measured. Single-colour pyrometers are proportional to the amount of radiation in the band; two-colour pyrometers are proportional to the ratio of the amount of radiation in the two bands.
Infrared system: infrared thermometer by the optical system, photodetector, signal amplifier and signal processing, display output and other components. Optical system convergence of its field of view of the target infrared radiation energy, the size of the field of view by the thermometer's optical parts and their location to determine. The infrared energy is focused on the photodetector and transformed into a corresponding electrical signal. The signal is converted into the temperature value of the target after passing through the amplifier and signal processing circuitry and being corrected for the target emissivity according to the algorithm and target emissivity in the instrument.
