Two-colour infrared thermometer surface emission
Any infrared measuring instrument obtains equipment temperature information by measuring the infrared radiation power on the surface of 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 different surface emissivities of the target. In other words, for the same radiation power, the lower the emissivity, the higher the temperature will be displayed. Because the surface emissivity of an object is mainly determined by the material properties and surface state (such as surface oxidation, coating material, roughness and contamination 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 target being inspected, and input this value into the computer as an important parameter for calculating temperature or adjust the ε correction value of the infrared measuring instrument so that all The measured temperature output is emissivity corrected. Two other countermeasures to eliminate the impact of emissivity on test results are: when using an infrared thermal imaging camera for measurement, the emission must be corrected, and the emissivity value of the surface of the component under test must be found and the emissivity corrected to obtain a reliable temperature measurement results to improve the reliability of detection; for equipment components with frequent failures in infrared detection, 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 single-color wideband temperature measurement mode to the emissivity in the single-color narrowband temperature measurement mode. It is used when calculating the measured temperature in the dual-color temperature measurement mode. Since the emissivity of the narrowband mode cannot be adjusted, it is calculated by dividing the monochromatic broadband emissivity by the slope value.
If you need to pay attention to the narrowband temperature, adjust the slope and broadband emissivity so that the narrowband emissivity is greater than 1.00 (or less than 0.10).
Emissivity is a measure of an object's ability to radiate infrared light. This value can range from 0 (specular) to 1.0 (blackbody). If the emissivity is set to a value greater than the actual emissivity, the reading of the sensor head will be low. For example, if the actual emissivity of the object is 0.9 and the setting value is 0.95, the measured temperature will be lower.
How to determine slope
Effective methods of determining slope include measuring the object's temperature using a probe (such as an RTD), thermocouple, or other suitable method. After obtaining the actual temperature, adjust the emissivity setting until the temperature reading of the sensor head is equal to the actual measured temperature, and the correct slope value is obtained.
How to determine emissivity
1. Use a probe (such as RTD), thermocouple, or other suitable method to measure the actual temperature of the object. Adjust the emissivity value 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 approximately 0.98. Set the emissivity to 0.98 and measure the temperature of the blackened part. Then measure the area adjacent to the blackened part of the object and adjust the emissivity until the temperature reading is equal to the actual temperature. The correct emissivity is now obtained.
3 Optimize surface temperature measurement according to the following guidelines:
1. Use a measuring instrument to measure the emissivity of an object.
2. Try to avoid reflection; shield the object from high-temperature heat sources in the surrounding environment.
3. When the object temperature is high, if there are several partially overlapping wavelengths available, choose the shorter wavelength.
4. For translucent materials, such as glass; when measuring temperature, ensure that the background temperature is uniform and lower than the object temperature.
5. When the emissivity is less than 0.9, the sensor head and the surface of the target object should be kept as vertical as possible. Do not allow the angle between the axis of the sensor head and the normal line of the object surface to be greater than 45°
