Infrared thermometer signal processing function explanation
Explanation of the signal processing function of the infrared thermometer: signal processing function: measuring the discrete process (such as parts production) is different from the continuous process, and the infrared thermometer is required to have a signal processing function (such as peak hold, valley hold, average value). For example, when measuring the temperature of the glass on the conveyor belt, it is necessary to use the peak value to hold, and the output signal of its temperature is sent to the controller.
Infrared temperature measurement technology is playing an important role in product quality control and monitoring, equipment online fault diagnosis, safety protection and energy saving. 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 contact temperature measurement methods, infrared temperature measurement has the advantages of fast response time, non-contact, safe use and long service life.
The selection of infrared thermometers can be divided into three aspects: performance indicators, such as temperature range, spot size, working wavelength, measurement accuracy, response time, etc.; environmental and working conditions, such as ambient temperature, window, display and output, protection Accessories, etc.; other selection aspects, such as ease of use, maintenance and calibration performance, and price, also have a certain impact on the choice of thermometer. With the continuous development of technology and technology, the best design and new progress of infrared thermometers provide users with various functions and multi-purpose instruments, expanding the choice.
The signal processing function of the infrared thermometer is explained to determine the temperature measurement range: the temperature measurement range is the most important performance index of the thermometer. Each type of thermometer has its own specific temperature range. Therefore, the user's measured temperature range must be considered accurately and comprehensively, neither too narrow nor too wide. According to the law of blackbody radiation, the change of radiation energy caused by temperature in the short-wave band of the spectrum will exceed the change of radiation energy caused by emissivity error. Therefore, it is better to use short-wave as much as possible when measuring temperature.
Determine the target size: Infrared thermometers can be divided into single-color thermometers and two-color thermometers (radiation colorimetric thermometers) according to the principle. For a monochromatic thermometer, when measuring temperature, the area of the target to be measured should fill the field of view of the thermometer. It is recommended that the measured target size exceed 50% of the field of view. If the target size is smaller than the field of view, the background radiation energy will enter the visual and acoustic symbols of the thermometer and interfere with the temperature measurement readings, causing errors. Conversely, if the target is larger than the pyrometer's field of view, the pyrometer will not be affected by background outside the measurement area.
The signal processing function of the infrared thermometer is explained to determine the optical resolution (distance is sensitive) The optical resolution is determined by the ratio of D to S, which is the ratio of the distance D between the thermometer to the target and the diameter S of the measurement spot. If the thermometer must be installed far away from the target due to environmental conditions, and a small target must be measured, a thermometer with high optical resolution should be selected. The higher the optical resolution, i.e. increasing the D:S ratio, the higher the cost of the pyrometer.
Infrared Thermometer Signal Processing Function Explanation Determining the Wavelength Range: The emissivity and surface properties of the online pyrometer target material determine the spectral response or wavelength of the pyrometer. For high reflectivity alloy materials, there is low or varying emissivity. In the high temperature area, the best wavelength for measuring metal materials is near infrared, and the wavelength of 0.18-1.0μm can be selected. Other temperature zones can choose 1.6μm, 2.2μm and 3.9μm wavelength. 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 wavelengths of 1.0μm, 2.2μm and 3.9μm are used to measure the internal temperature of the glass (the glass to be tested must be very thick, otherwise it will pass through) wavelengths; For example, the wavelength of 3.43 μm is used for measuring polyethylene plastic film, and the wavelength of 4.3 μm or 7.9 μm is used for polyester. If the thickness is more than 0.4mm, choose 8-14μm wavelength; for example, measure CO2 in flame with narrow band 4.24-4.3μm wavelength, measure CO in flame with narrow band 4.64μm wavelength, measure NO2 in flame with 4.47μm wavelength.
The signal processing function of the infrared thermometer is explained to determine the response time: the response time indicates the reaction speed of the infrared thermometer to the measured temperature change, which is defined as the time required to reach 95% of the energy of the final reading. It is related to the photoelectric detector and signal processing It is related to the time constant of the circuit and display system. This is much faster than contact temperature measurement methods. If the moving speed of the target is very fast or when measuring a fast-heating target, a fast-response infrared thermometer should be selected, otherwise the sufficient signal response will not be achieved, and the measurement accuracy will be reduced. However, not all applications require a fast-response infrared thermometer. For static or target thermal processes where thermal inertia exists, the response time of the pyrometer can be relaxed. Therefore, the choice of the response time of the infrared thermometer should be adapted to the situation of the measured target.
