Non-contact temperature sensor

Its sensitive components are not in contact with the measured object, also known as non-contact temperature measuring instrument. This instrument can be used to measure the surface temperature of moving objects, small targets and objects with small heat capacity or rapid temperature changes (transient), and can also be used to measure the temperature distribution of the temperature field.
The most commonly used non-contact thermometers are based on the fundamental law of black body radiation and are called radiation thermometers. Radiation thermometry methods include brightness method (see optical pyrometer), radiation method (see radiation pyrometer) and colorimetric method (see colorimetric thermometer). All kinds of radiation temperature measurement methods can only measure the corresponding photometric temperature, radiation temperature or colorimetric temperature. Only the temperature measured for a black body (an object that absorbs all radiation and does not reflect light) is the true temperature. If you want to measure the real temperature of the object, you must correct the surface emissivity of the material. However, the surface emissivity of materials depends not only on temperature and wavelength, but also on surface state, coating film and microstructure, so it is difficult to measure accurately. In automatic production, it is often necessary to use radiation thermometry to measure or control the surface temperature of certain objects, such as the steel strip rolling temperature, roll temperature, forging temperature in metallurgy, and the temperature of various molten metals in smelting furnaces or crucibles . In these specific cases, the measurement of the emissivity of an object's surface is quite difficult. For automatic measurement and control of solid surface temperature, an additional reflector can be used to form a black body cavity together with the measured surface. The effect of additional radiation can increase the effective radiation and effective emissivity of the measured surface. Use the effective emissivity coefficient to correct the measured temperature through the instrument, and finally get the real temperature of the measured surface. The most typical additional mirror is a hemispherical mirror. The diffuse radiation on the measured surface near the center of the sphere can be reflected back to the surface by the hemispherical mirror to form additional radiation, thereby increasing the effective emissivity coefficient. In the formula, ε is the surface emissivity of the material, and ρ is the reflectivity of the mirror. As for the radiation measurement of the real temperature of the gas and liquid medium, the method of inserting the heat-resistant material tube to a certain depth to form a black body cavity can be used. The effective emission coefficient of the cylinder cavity after reaching thermal equilibrium with the medium is obtained by calculation. In automatic measurement and control, this value can be used to correct the measured cavity bottom temperature (ie medium temperature) to obtain the real temperature of the medium.