Determine the temperature range
Temperature measurement range is an important performance indicator of the thermometer. Such as TIME (Time), Raytek (Ray Thai) product coverage is -50 ℃-+3000 ℃, but this can not be done by a model of infrared thermometer. Each type of thermometer has its own specific temperature range. Therefore, the user's measured temperature range must be considered accurate and comprehensive, neither too narrow nor too wide. According to the law of black body radiation, the change in radiant energy caused by temperature in the short wavelength band of the spectrum will exceed the change in radiant energy caused by emissivity errors. Therefore, it is better to use short waves when measuring temperature.
Determine target size
Infrared thermometers can be divided into monochrome thermometers and dual-color thermometers (radiochromatic thermometers) according to the principle. For a monochrome thermometer, when measuring temperature, the area of the target to be measured should be filled with the field of view of the thermometer. It is recommended that the size of the target to be measured exceeds 50% of the field of view. If the size of the target is smaller than the field of view, the background radiant energy will enter the audiovisual notes of the thermometer and interfere with the temperature reading, causing errors. Conversely, if the target is larger than the field of view of the thermometer, the thermometer will not be affected by the background outside the measurement area.
Determine optical resolution (distance and sensitivity)
The optical resolution is determined by the ratio of D to S, which is the ratio of the distance D from the thermometer to the target to the measurement spot diameter S. If the thermometer must be installed away from the target due to environmental conditions, and you need to measure a small target, you should choose a thermometer with high optical resolution. The higher the optical resolution, the larger the D: S ratio, the higher the cost of the thermometer.
Determine the wavelength range
The emissivity and surface characteristics of the target material determine the spectral response or wavelength of the thermometer. For high reflectivity alloy materials, there is a low or varying emissivity. In the high temperature region, the best wavelength for measuring metal materials is near infrared, and a wavelength of 0.18-1.0 μm can be selected. Other temperature zones are available with wavelengths of 1.6 μm, 2.2 μm, and 3.9 μm. Since some materials are transparent at a certain wavelength, infrared energy will penetrate these materials, and a special wavelength should be selected for this material. For example, the internal temperature of the glass should be selected from 10μm, 2.2μm, and 3.9μm (the measured glass must be thick, otherwise it will transmit). The internal temperature of the glass should be selected from the 5.0μm wavelength. The lower region should be selected from the 8-14μm wavelength. For measurement of polyethylene plastic film, a wavelength of 3.43 μm is used, and for polyacetate, a wavelength of 4.3 μm or 7.9 μm is used. If the thickness exceeds 0.4mm, choose a wavelength of 8-14μm. For another example, use a narrow band of 4.24-4.3μm for measuring C02 in a flame, use a narrowband of 4.64μm for measuring C0 in a flame, and use a 4.47μm for measuring N02 in a flame.
Determine response time
The response time indicates the response speed of the infrared thermometer to changes in the measured temperature. It is defined as the time required to reach 95% of the reading (two-color colorimetric fiber requires only 5% energy). The circuit and the time constant of the display system are related. The response time of the new infrared thermometer can reach 1ms. This is much faster than the contact temperature measurement method. If the target moves fast or measures a fast-heated target, a fast-response infrared thermometer should be selected; otherwise, a sufficient signal response cannot be achieved, which will reduce the measurement accuracy. However, not all applications require fast response infrared thermometers. When there is thermal inertia for stationary or target thermal processes, the response time of the thermometer can be relaxed. Therefore, the choice of the response time of the infrared thermometer should be adapted to the situation of the measured target.
I believe that through the introduction above, when we choose an infrared thermometer, we should be able to choose a product suitable for our use.
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