Radiation temperature measurement influenced by object emissivity
Almost all actual objects that exist in nature are not blackbodies. The radiation amount of all actual objects depends not only 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 condition, and environmental conditions that make up the object. Therefore, in order for the blackbody radiation law to apply to all actual objects, it is necessary to introduce a proportional coefficient related to material properties and surface conditions, namely emissivity. This coefficient represents the closeness between the thermal radiation of an actual object and the blackbody radiation, with a value between zero and values less than 1. According to the radiation law, 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, physicochemical structure, and material thickness, etc.
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 within the wavelength range, while the two-color thermometer is proportional to the radiation between the two wavelength ranges.
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 amplified and processed by a signal processing circuit, and converted into the temperature value of the measured target after being corrected according to the algorithm of the instrument's internal therapy and target emissivity.
