Infrared thermometer components and working principle
Infrared system: Infrared thermometer by the optical system, photoelectric, 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. Infrared energy is focused on the photoelectric and transformed into a corresponding electrical signal. This signal is converted into a temperature value for the target after passing through amplifiers and signal processing circuits and being corrected for the target emissivity according to the algorithms used in the instrument. Understanding of the infrared thermometer operating principle, technical specifications, environmental conditions and operation and maintenance is the basis for the user to correctly select and use the infrared thermometer.
In addition, should also consider the target and the pyrometer is located in the environmental conditions, such as temperature, atmosphere, pollution and interference and other factors on the performance indicators and correction methods. Any object with a temperature above ** zero emits infrared light. The infrared thermometer receives and measures the wavelength of the infrared rays emitted by the object, and the corresponding temperature can be obtained. All objects with temperatures above **zero degrees are constantly emitting infrared radiant energy into the surrounding space. The size of the object's infrared radiation energy and its distribution by wavelength - and its surface temperature has a very close relationship. Therefore, through the measurement of the infrared energy radiated by the object itself, it will be able to accurately determine its surface temperature, which is the objective basis for infrared radiation temperature measurement. Blackbody radiation law: blackbody is an idealised radiator, which absorbs all wavelengths of radiant energy, no energy reflection and transmission, the emissivity of its surface is 1.
It should be noted that there is no real black body in nature, but in order to clarify and obtain the law of infrared radiation distribution, in the theoretical study must choose the appropriate model, which is Planck put forward the body cavity radiation quantisation vibronic model, which led to Planck's law of the black body radiation, that is, the wavelength of the black body spectral radiance, this is the starting point for all infrared radiation theory, so called the law of black body radiation. The effect of object emissivity on radiometric temperature measurement: the existence of real objects in nature, almost all are not black bodies. All the actual object of the radiation in addition to relying on the wavelength of the radiation and the temperature of the object, but also with the composition of the object's material type, preparation methods, thermal processes, as well as the surface state and environmental conditions and other factors. The infrared energy is focussed on the photodetector and converted into a corresponding electrical signal. This signal is converted into the temperature value of the target by an amplifier and signal processing circuitry in accordance with the instrument's internal algorithm and target emissivity correction.
Therefore, in order to make the blackbody radiation law applicable to all real objects, it is necessary to introduce a proportionality coefficient, i.e. emissivity, related to the nature of the material and the state of the surface. This coefficient represents the proximity of the thermal radiation of the actual object to the blackbody radiation and has a value between zero and a value less than one. According to the law of radiation, as long as we know the emissivity of the material, we know the infrared radiation characteristics of any object. The main factors affecting emissivity are: material type, surface roughness, physical and chemical structure and material thickness. When measuring the temperature of a target with an infrared radiation pyrometer, the target's infrared radiation within its band is first measured, and then the temperature of the target is calculated by the pyrometer.
