The infrared thermometer must be correctly selected
Infrared temperature measurement technology is playing an important role in product quality control and monitoring, equipment online fault diagnosis, protection and energy saving in our country. In the past two decades, non-contact infrared thermometers have developed rapidly in technology, their performance has been continuously improved, their scope of application has also been continuously expanded, and their market share has increased year by year. Compared with the contact temperature measurement method, infrared temperature measurement has the advantages of fast response time, non-contact, safe use and long service life. The digital noise meter also plays a certain role in measuring the sound level.
The working principle of the external measuring line thermometer:
Understanding the working principle, technical indicators, environmental working conditions, operation and maintenance of the infrared thermometer outside the group is to help users choose and use the infrared thermometer correctly.
All objects whose temperature is higher than the absolute zero are constantly emitting infrared radiation energy to the surrounding space. The infrared radiation characteristics of an object—the size of the radiation energy and its distribution by wavelength—has a very close relationship with its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.
Black body radiation law of pyrometer:
A blackbody is an idealized radiator that absorbs all wavelengths of radiant energy, has no reflection or transmission of energy, and has an emissivity of 1 on its surface. It should be pointed out that there is no real black body in nature, but in order to clarify and obtain the distribution law of infrared radiation, an appropriate model must be selected in theoretical research, which is the quantized oscillator model of body cavity radiation proposed by Jintai Keyi, so that This is the starting point of all infrared radiation theories, so it is called the law of black body radiation.
The influence of emissivity of thermometer object on radiation temperature measurement:
The actual objects that exist in nature are almost not black bodies. The radiation amount of all actual objects depends not only on the radiation wavelength and the temperature of the object, but also on the type of material constituting the object, the preparation method, the thermal process, the surface state and the environmental conditions. Therefore, in order to make the law of black body radiation applicable to all practical objects, a proportional coefficient related to material properties and surface states must be introduced, that is, emissivity. This coefficient indicates how close the thermal radiation of the actual object is to the black body radiation, and its value is between zero and a value less than 1. According to the law of radiation, as long as the emissivity of the material is known, the infrared radiation characteristics of any object can be known.
The main factors affecting the emissivity of infrared thermometers are:
Material type, surface roughness, physical and chemical structure and material thickness, etc.
When using an infrared radiation thermometer to measure the temperature of a target, it is first necessary to measure the infrared radiation of the target within its band range, and then the temperature of the measured target is calculated by the thermometer. Monochromatic pyrometers are proportional to the amount of radiation in a band: dual-color pyrometers are proportional to the ratio of the amount of radiation in the two bands.
The infrared thermometer must correctly correspond to the selection of the infrared system:
The infrared thermometer is composed of optical system, photoelectric detector, signal amplifier, signal processing, display output and other parts. The optical system gathers the infrared radiation energy of the target in its field of view, and the size of the field of view is determined by the optical parts of the thermometer and its position. Infrared energy is focused on a photodetector and converted into a corresponding electrical signal. The signal passes through the amplifier and the signal processing circuit, and is converted into the temperature value of the measured target after being corrected according to the algorithm of the internal treatment of the instrument and the emissivity of the target.
