Composition and working principle of infrared thermometer
Infrared system: The infrared thermometer consists of an optical system, optoelectronics, 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 photoelectricity and converted into corresponding electrical signals. The signal is converted into the temperature value of the tested target after being amplified and processed by the signal processing circuit, and corrected according to the algorithm of the instrument's internal treatment and the target emissivity. Understanding the working principle, technical specifications, environmental working conditions, operation and maintenance of infrared thermometers is the foundation for users to choose and use infrared thermometers correctly.
In addition, the environmental conditions of the target and thermometer, such as temperature, atmosphere, pollution, and interference, should also be considered for their impact on performance indicators and correction methods. Any object with a temperature above relative zero will emit infrared radiation. The infrared thermometer receives and measures the wavelength of the infrared emitted by the object, and can obtain the corresponding temperature. All objects with temperatures above relative zero are constantly emitting infrared radiation energy into the surrounding space. The size and wavelength distribution of infrared radiation energy of an object are closely related to its surface temperature. Therefore, by measuring the infrared energy emitted by an object itself, its surface temperature can be accurately measured, which is the objective basis for infrared radiation temperature measurement. Blackbody radiation law: A blackbody is an idealized radiator that absorbs radiation energy of all wavelengths without any reflection or transmission of energy. Its surface emissivity is 1.
It should be pointed out that there is no real blackbody in nature, but in order to understand and obtain the distribution law of infrared radiation, it is necessary to choose a suitable model in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, which derives the law of Planck blackbody radiation, that is, the spectral radiance of blackbody expressed in wavelength. This is the starting point of all infrared radiation theories, hence the blackbody radiation law. The influence of object emissivity on radiation temperature measurement: Almost all actual objects present in nature are not black bodies. The radiation amount of all actual objects is not only dependent 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 state, and environmental conditions that make up the object. Infrared energy is focused on the photoelectric detector and converted into corresponding electrical signals. The signal is converted into the temperature value of the tested target after being calibrated by the amplifier and signal processing circuit according to the internal algorithm of the instrument and the target emissivity.
Therefore, in order for the blackbody radiation law to apply to all practical objects, it is necessary to introduce a proportional coefficient related to material properties and surface states, namely emissivity. This coefficient represents the proximity between the thermal radiation of the actual object and the blackbody radiation, with a value between zero and a value less than 1. According to the law of radiation, as long as the emissivity of a material is known, the infrared radiation characteristics of any object are known. The main factors that affect emissivity are material type, surface roughness, physicochemical structure, and material thickness. 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 amount within the band; The ratio of the dual color thermometer to the radiation of the two bands is proportional
