Is the thermometer affected by ambient atmospheric attenuation?
Due to the fact that the infrared radiation energy on the surface of the tested electrical equipment is transmitted through the atmosphere to the infrared detection instrument, it will be attenuated by the absorption and attenuation of gas molecules such as water vapor, carbon dioxide, and carbon monoxide in the atmosphere, as well as the scattering of suspended particles in the air. The attenuation of the radiation energy transmission of the equipment decreases with the distance between the detection instrument and the tested equipment, reducing the transmittance of the radiation emitted by the tested equipment.
So its attenuation increases with distance, reducing the radiation contrast between the faulty and normal parts of the tested equipment. It can also cause the temperature displayed by the infrared instrument to be lower than the actual temperature value of the tested fault point due to the decrease in target energy received by the instrument, resulting in missed detection or misdiagnosis. This is particularly disadvantageous when detecting equipment failures with low temperature rise. As the detection distance increases, the influence of atmospheric composition will become increasingly significant. And in order to obtain the accuracy of the target temperature, the following measures must be taken: try to choose a season when the environment is relatively dry and clean for testing; Minimize the detection distance as much as possible without affecting safety, and make reasonable distance corrections to the temperature measurement results in order to obtain the actual temperature value.
Reasons for inaccurate measurement of infrared thermometers
The relationship between the size of the temperature measurement target and the temperature measurement distance
External thermometers can be divided into monochrome thermometers and two-color thermometers (radiation colorimetric thermometers) based on their principles. For monochrome thermometers, the area of the measured target should fill the thermometer's field of view during temperature measurement. It is recommended that the size of the target being tested exceed 50% of the field of view size. 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 reading, causing errors. On the contrary, 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
The effective diameter of measurable targets varies at different distances, so attention should be paid to the target distance when measuring small targets. The distance coefficient K of an infrared thermometer is defined as the ratio of the distance L of the measured target to the diameter D of the measured target, i.e. K=L/D.
