Surface emission of two-color pyrometers
Any infrared measuring instrument obtains the temperature information of the equipment by measuring the infrared radiation power on the surface of the electrical equipment. And when the infrared diagnostic instrument receives the same infrared radiation power from the target, different detection results will be obtained due to the different surface emissivity of the target. That is to say, for the same radiation power, the lower the emissivity, the higher the temperature will be displayed. Because the surface emissivity of the object is mainly determined by the material properties and surface state (such as surface oxidation, coating material, roughness and pollution state, etc.). Therefore, in order to accurately measure the temperature of electrical equipment using infrared thermal imaging instruments, it is necessary to know the emissivity value of the inspected target, and input this value into the computer as an important parameter for calculating the temperature, or adjust the ε correction value of the infrared measuring instrument, so that all The measured temperature output value is corrected for emissivity. The other two countermeasures to eliminate the influence of emissivity on the test results are: when using an infrared thermal imager for measurement, it is necessary to correct the emissivity, find out the emissivity value of the surface of the device under test and correct the emissivity, so as to obtain a reliable The temperature measurement results can improve the reliability of detection; for infrared detection equipment components with frequent failures, in order to make the detection results have good comparability, the method of applying appropriate paint can be used to increase and stabilize the emissivity value, so that Obtain the true temperature of the surface of the device under test.
The slope is the ratio of the emissivity in the monochrome broadband temperature measurement mode to the emissivity in the monochrome narrowband temperature measurement mode, which will be used when calculating the measured temperature in the two-color temperature measurement mode. Since the emissivity of the narrowband mode cannot be adjusted, it is obtained by dividing the monochromatic broadband emissivity by the slope value.
If you need to pay attention to the narrowband temperature, make the narrowband emissivity greater than 1.00 (or less than 0.10) by adjusting the slope and broadband emissivity.
Emissivity is a measure of an object's ability to radiate infrared light. This value can be from 0 (mirror) to 1.0 (black body), if the emissivity setting is greater than the actual emissivity, the sensor head will read low. For example, if the actual emissivity of the object is 0.9 and the set value is 0.95, the measured temperature will be low.
how to determine slope
Effective methods of determining slope include measuring the temperature of the object with a probe (such as an RTD), a thermocouple, or other suitable means. After obtaining the actual temperature, adjust the setting of the emissivity until the temperature reading of the sensor head is equal to the actual measured temperature, that is, the correct slope value is obtained.
How to Determine Emissivity
1. Use a probe (such as RTD), thermocouple, or other suitable methods to measure the actual temperature of the object. Adjust the value of emissivity until the temperature reading of the sensor head is the same as the actual temperature, that is, the correct emissivity is obtained.
2. If part of the surface of the object can be coated, the surface of the object can be blackened with matte carbon black. At this time, the emissivity is about 0.98. Set the emissivity to 0.98, and measure the temperature of the blackened part. Finally, measure the area adjacent to the blackened part of the object and adjust the emissivity until the temperature reading equals the actual temperature. The correct emissivity is then obtained.
