What is an infrared thermometer working principle
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 approach to infrared radiation energy, the size of the field of view by the pyrometer optical parts and their orientation determined. Infrared energy focused on the photodetector and transformed into a corresponding electrical signal. The signal passes through the amplifier and signal processing circuitry, and in accordance with the instrument's built-in algorithms and approach emissivity correction, ambient temperature compensation is transformed into the temperature value of the measured approach.
In nature, all objects with temperature higher than ** zero degrees are constantly announcing infrared radiation energy to the surrounding space. The size of the object's infrared radiation energy and its distribution by wavelength - and its external temperature has a very close relationship. Therefore, through the measurement of infrared energy radiated by the object itself, it will be able to accurately determine the temperature of its appearance, which is based on the objective basis of infrared radiation temperature measurement. Blackbody is an idealised radiator, it absorbs all wavelengths of radiant energy, no energy reflection and transmission, the emissivity of its appearance is 1.
However, the existence of practical objects in nature, almost all are not a blackbody, in order to clarify and obtain the distribution of infrared radiation law, in the theoretical study must choose the appropriate model, which is Planck proposed by the body cavity radiation quantisation vibronic model, and then derived the law of Planck's blackbody radiation, that is, expressed in wavelengths of the blackbody spectral radiance, this is the starting point of all infrared radiation theory, it is called Blackbody radiation law. All practical object 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 appearance of the situation and environmental conditions and other factors.
Consequently, in order to make the laws of blackbody radiation applicable to all practical objects, it is necessary to introduce a proportionality coefficient, i.e. emissivity, related to the nature of the material and the condition of the exterior. This coefficient represents the proximity of the thermal radiation of the practical object to the blackbody radiation, and its value is between zero and a value less than one. According to the law of radiation, only need to know the emissivity of the material, we know the infrared radiation characteristics of any object. The main factors affecting the emissivity in: the type of material, appearance roughness, physical and chemical layout and thickness of the material.
When using infrared radiation thermometer to measure the temperature of the policy first to measure the policy in its band range of infrared radiation, and then by the thermometer to calculate the temperature of the measured policy. Single-colour pyrometer and the amount of radiation in the band is proportional to the two-colour pyrometer and the ratio of the amount of radiation in the two bands is proportional.
