What is the Principle and Classification of Infrared Thermometers?
1. Infrared principle: Any object whose temperature is above * * zero degrees (-273 ℃) will emit thermal radiation outward. The difference in temperature of the object will result in a difference in the energy radiated and the wavelength of the radiation wave. However, infrared radiation is always included. For objects below a thousand degrees Celsius, the strongest electromagnetic waves hit by their thermal radiation are infrared waves. Therefore, by measuring the infrared radiation of the object itself, its appearance temperature can be accurately determined. This is the objective basis and fundamental principle of infrared thermometer temperature measurement.
A blackbody is an idealized radiator that absorbs radiation energy of all wavelengths without any reflection or transmission of energy, and its emissivity is 1. However, almost all real objects in the natural world are not blackbodies. In order to clarify and obtain the diffusion law of infrared radiation, a suitable model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, which derived Planck's law of blackbody radiation, that is, the spectral radiance of blackbody radiation expressed in wavelength. This is the starting point of all infrared radiation theories, hence it is called the blackbody radiation law.
The radiation level of all real objects depends not only on the radiation wavelength and temperature of the object, but also on factors such as the type of material used to construct the object, preparation methods, thermal history, and appearance and conditions. Therefore, in order to apply the blackbody radiation law to all real objects, it is necessary to introduce a proportionality coefficient related to the material properties and appearance states, namely emissivity. This coefficient represents the proximity level between the thermal radiation of real objects and blackbody radiation, with a value between 0 and 1. According to the law of radiation, as long as the emissivity of a material is known, the infrared radiation characteristics of any object can be determined. The important factors affecting emissivity of yarn include material type, surface roughness, physical and chemical layout, and material thickness.
2. The working principle and layout of an infrared thermometer: In the natural world, all objects with temperatures above * * zero degrees continuously emit infrared radiation energy into the surrounding space. The size and wavelength of an object's infrared radiation energy are closely related to its appearance temperature. Therefore, by measuring the infrared energy radiated by an object itself, its external temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.
The temperature measurement principle of an infrared thermometer is to convert the radiation energy of the infrared emitted by an object (such as molten steel) into an electrical signal. The magnitude of the infrared radiation energy corresponds to the temperature of the object (such as molten steel) itself, and the temperature of the object (such as molten steel) can be determined by the change in the magnitude of the electrical signal. The infrared thermometer consists of an optical system, photoelectric detector, signal amplifier, signal processing punishment, performance output and other departments. The optical system concentrates the target infrared radiation energy 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 by an amplifier and processed by a penalty circuit, and then converted to the temperature value of the target after correction based on the algorithm of the instrument's internal therapy and the target emissivity.
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 calculate the temperature of the target using the thermometer disk. The principle of infrared thermometers can be divided into monochromatic thermometers and two-color thermometers (radiation colorimetric thermometers). Monochromatic thermometers are proportional to the amount of radiation within the wavelength band; The dual color thermometer is proportional to the ratio of radiation in two bands.
