The effect of an object's emissivity on the measurement of radiation temperature
Almost all actual objects that exist in nature are not black bodies. The radiation amount of all actual objects is not only dependent on the wavelength of radiation and the temperature of the object, but also on factors such as the type of material, preparation method, thermal process, surface state, and environmental conditions that make up the object. Therefore, in order for the blackbody radiation law to apply to all practical objects, it is necessary to introduce a proportional coefficient related to material properties and surface states, namely emissivity. This coefficient represents the proximity between the thermal radiation of the actual object and the blackbody radiation, with a value between zero and a value less than 1. 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 include material type, surface roughness, physicochemical structure, and material thickness.
When measuring the temperature of a target using an infrared radiation thermometer, the first step is to measure the infrared radiation of the target within its wavelength range, and then the thermometer calculates the temperature of the measured target. The monochromatic thermometer is proportional to the radiation amount within the band; The dual color thermometer is proportional to the ratio of radiation in both bands.
Infrared system: The infrared thermometer consists of an optical system, a photodetector, a signal amplifier, signal processing, display output, and other components. The optical system gathers 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 their positions 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 tested target after being amplified and processed by the signal processing circuit, and corrected according to the algorithm of the instrument's internal treatment and the target emissivity.
