How Object Emissivity Affects Radiation Temperature Measurement of Thermometers
Practically all real objects existing in nature are not blackbodies. Apart from the radiation wavelength and object temperature, the radiant quantity of any real object is also related to factors such as material type, fabrication method, thermal process, surface condition and environmental conditions. Therefore, to make the blackbody radiation laws applicable to all real objects, a proportional coefficient associated with material properties and surface conditions must be introduced, namely emissivity. This coefficient indicates how closely the thermal radiation of a real object approximates blackbody radiation, and its value ranges from zero to less than 1. According to radiation laws, the infrared radiation characteristics of any object can be obtained once the emissivity of its material is known.
The main factors affecting emissivity include material type, surface roughness, physicochemical structure and material thickness.
When measuring the temperature of a target with an infrared radiation thermometer, the instrument first measures the amount of infrared radiation of the target within its wavelength band, and then calculates the temperature of the measured target. A monochromatic thermometer is proportional to the radiant quantity within the wavelength band; a two-color thermometer is proportional to the ratio of radiant quantities in two wavelength bands.
Infrared System: An infrared thermometer consists of an optical system, photoelectric detector, signal amplifier, signal processing unit, display and output modules. The optical system collects the infrared radiant energy of the target within its field of view. The size of the field of view is determined by the thermometer's optical components and their positions. The infrared energy is focused onto the photoelectric detector and converted into corresponding electrical signals. Processed by the amplifier and signal processing circuits, these signals are converted into the temperature value of the measured target in accordance with the instrument's internal algorithms and target emissivity correction.
