To adjust the emissivity of an infrared thermometer, follow these steps
Infrared (IR) radiation
Infrared radiation is everywhere and never-ending. The greater the temperature difference between objects, the more obvious the radiation phenomenon is. The vacuum can transmit the infrared radiation energy emitted by the sun to the earth through 93 million miles of space and time, where it can be absorbed by us and bring us warmth. When we stand in front of a refrigerated food cabinet in a shopping mall, the infrared radiated heat emitted by our bodies is absorbed by the refrigerated food, making us feel very cool. In both examples, the radiation effect is very obvious, and we can clearly feel the changes and feel its presence.
When we need to quantify the effect of infrared radiation, we need to measure the temperature of infrared radiation, and in this case an infrared thermometer is used. Different materials have different infrared radiation characteristics. Before using an infrared thermometer to read the temperature, we must first understand the basic principles of infrared radiation measurement and the infrared radiation characteristics of the specific material being measured.
Infrared radiation rate = absorptivity + reflectivity + transmittance
No matter what kind of infrared radiation is emitted, it will be absorbed, so absorption rate = emissivity. What the infrared thermometer reads is the infrared radiation energy emitted by the surface of the object. The infrared radiometer cannot read the infrared radiation energy lost in the air. Therefore, in actual measurement work, we can ignore the transmittance, so that we get a Basic infrared radiation measurement formula:
Infrared radiance = emissivity - reflectivity
Reflectivity is inversely proportional to emissivity. The stronger an object's ability to reflect infrared radiation, the weaker its own ability to infrared radiation. The reflectivity of an object can generally be judged by visual inspection. New copper has a higher reflectivity but a lower emissivity (0.07-0.2), and oxidized copper has a lower reflectivity and a higher emissivity (0.6-0.7 ), copper blackened by heavy oxidation has an even lower reflectivity and a correspondingly higher emissivity (0.88). Most painted surfaces have very high emissivity (0.9-0.95) and negligible reflectivity.
For most infrared thermometers, all that needs to be set is the rated emissivity of the material being measured. This value is usually preset to 0.95, which is sufficient for measuring organic materials or painted surfaces.
By adjusting the emissivity of the thermometer, the problem of insufficient infrared radiation energy on the surface of some materials can be compensated, especially for metal materials. The impact of reflectivity on the measurement needs to be considered only when there is a high-temperature infrared radiation source near the surface of the object to be measured and reflects it.
