The main considerations when choosing an infrared thermometer are the following:
(1) In terms of performance indicators, such as:
Temperature measurement range: Each type of thermometer has its own specific temperature measurement range, which should be neither too narrow nor too wide. Generally speaking, the narrower the temperature measurement range, the higher the resolution of the output signal for monitoring temperature. Accuracy and reliability are easy to solve. If the temperature measurement range is too wide, the temperature measurement accuracy will be reduced.
Working wavelength: According to the blackbody radiation law, the change in radiant energy caused by temperature in the short-wavelength band of the spectrum will exceed the change in radiated energy caused by the emissivity error. Therefore, it is better to use short wavelength when measuring temperature, but it must also be Consider the factors of emissivity in combination with the object being detected:
The emissivity and surface properties of the target material determine the corresponding wavelength of the thermometer's spectrum. For high reflectivity alloy materials, there are low or varying emissivities. In high-temperature areas, the wavelength used to measure metal materials is near-infrared, and 0.8~1.0μm can be used. Other temperature zones are available in 1.6, 2.2 and 3.9μm. Since some materials are transparent at certain wavelengths, infrared energy will penetrate these materials. Special wavelengths should be selected for this material. For example, when measuring the internal temperature of glass, wavelengths 1.0, 2.2 and 3.9μm are used (the glass to be measured must be very thick. Otherwise, it will penetrate); when measuring the glass surface temperature, 5.0μm is used; when measuring the low temperature area, 8~14μm is suitable. For example, when measuring polyethylene plastic film, 3.43μm is used, polyester is used 4.3 or 7.9μm, and when the thickness exceeds 0.4mm, 3.43μm is used. 8~14μm, for example, narrow band 4.64μm is used to measure CO in flame, 4.47μm is used to measure NO2 in flame, etc.
Spot size: The area of the thermometer measurement point is called the "spot size". In order to obtain the best temperature reading, the distance between the thermometer and the test target must have a suitable range. The farther away from the target, the The spot size is larger. Therefore, the ratio of distance to spot size, or D:S, should be paid attention to in the application. When determining the measurement distance, care should be taken to make the target diameter equal to or larger than the measured light spot size. If the target is smaller than the spot size being measured, the thermometer will be measuring the temperature of the background object at the same time, reducing the accuracy of the reading.
