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Basic content introduction of non contact pyrometer

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Basic content introduction of non contact pyrometer

(Summary description)The sensitive components of non contact pyrometer do not touch each other with the measured object, also known as non-contact temperature measuring instrument.

Basic content introduction of non contact pyrometer

(Summary description)The sensitive components of non contact pyrometer do not touch each other with the measured object, also known as non-contact temperature measuring instrument.

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The sensitive components of non contact pyrometer do not touch each other with the measured object, also known as non-contact temperature measuring instrument. This kind of 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 commonly used non contact pyrometer is based on the basic law of blackbody radiation and is called a radiation thermometer. Radiation thermometry includes the luminance method (see optical pyrometer), radiation method (see radiation pyrometer) and colorimetric method (see colorimetric thermometer). The radiation temperature measurement method of non contact pyrometer can only measure the corresponding luminosity 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 determine the true temperature of an object, you must correct the surface emissivity of the material. The surface emissivity of a material not only depends on temperature and wavelength, but also on the surface state, coating film and microstructure, so it is difficult to accurately measure. In automated production, it is often necessary to use non-contact pyrometer to measure or control the surface temperature of certain objects, such as steel strip rolling temperature, roll temperature, forging temperature in metallurgy, and the temperature of various molten metals in smelting furnaces or crucibles. Under these specific circumstances, the measurement of the surface emissivity of an object is quite difficult. For the automatic measurement and control of the solid surface temperature, an additional mirror can be used to form a black body cavity together with the measured surface. The influence of additional radiation can increase the effective radiation and effective emission coefficient of the measured surface. Use the effective emission coefficient to correct the measured temperature through the meter, and finally get the true temperature of the measured surface. The most typical additional mirror is a hemispherical mirror. The diffuse radiation energy of the measured surface near the center of the ball is reflected back to the surface by the hemispherical mirror to form additional radiation, so that the non contact pyrometer improves the effective emission coefficient. The formula is the material surface emissivity and the reflectivity of the reflector. As for the radiation measurement of the true temperature of gas and liquid media, a method of inserting a heat-resistant material tube to a certain depth to form a black body cavity can be used. The effective emission coefficient of the cylindrical cavity after reaching thermal equilibrium with the medium is calculated by calculation. In automatic measurement and control, this value can be used to correct the measured cavity bottom temperature (that is, the temperature of the medium) to obtain the true temperature of the medium.

 

Advantages of non contact pyrometer:

 

The upper limit of non contact pyrometer measurement is not limited by the temperature resistance of the temperature sensing element, so in principle there is no limit on the maximum measurable temperature. For high temperatures above 1800°C, non-contact temperature measurement methods are mainly used. With the development of infrared technology, radiation temperature measurement has gradually expanded from visible light to infrared. It has been adopted from below 700°C to room temperature with high resolution.

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