How Does Surface Emissivity Affect Infrared Thermometers?
Leave a message
Infrared thermometers are widely used in many fields such as industry, medical treatment, and food safety due to their advantages of non-contact, fast response, and easy operation. However, in the actual temperature measurement process, a key factor affecting the accuracy of the reading is often overlooked, and that is the "surface emissivity" of the object being measured. Surface emissivity not only determines the intensity of radiation energy received by the infrared thermometer, but is also directly related to the accuracy of the measurement results. This article will focus on this core and deeply explore the principle and practical significance of the influence of surface emissivity on the performance of infrared thermometers.
Surface emissivity refers to the ability of an object's surface to radiate infrared energy, compared to a black object. The emissivity of an ideal blackbody is 1, which can completely absorb and re-radiate electromagnetic radiation in all bands; while the emissivity of objects in real life is usually lower than 1. Emissivity may vary depending on materials, colors, surface roughness and temperature conditions. This means that at the same temperature, objects with different emissivities will release different infrared energy intensities, which will affect the reception and judgment of the infrared thermometer.
How do infrared thermometers rely on surface emissivity to work?
The basic principle of infrared thermometer is to estimate the temperature by detecting the infrared radiation emitted by the surface of the object. Since the intensity of infrared radiation has a certain mathematical relationship with the temperature of the object surface, the thermometer will convert the received radiation intensity into a temperature display. However, this calculation must be based on an accurate emissivity value. If the set emissivity deviates greatly from the actual value, even if the accuracy of the device itself is high, it will lead to serious deviations in temperature readings. Therefore, thermometers usually provide an emissivity adjustment function when leaving the factory, so that users can adjust it according to the material of the object being measured.
How Do Differences In Emissivity Lead To Temperature Measurement Errors?
If the emissivity set by the infrared thermometer is higher than the actual value, the instrument will think that the received infrared energy is less, and will misjudge that the temperature is too low; conversely, it will misjudge that the temperature is too high. For example, polished metal surfaces generally have lower emissivity, while oxidized metal or painted surfaces have higher emissivity. If the same emissivity parameter is used to measure these two different surfaces, the temperatures displayed by the infrared thermometer will be significantly different even if their actual temperatures are the same. This error will not only mislead users, but may also cause major problems in the process, especially in situations where temperature is extremely precise, such as heat treatment, electronic component manufacturing, or medical temperature measurement.
How To Identify And Set The Appropriate Emissivity?
Correctly identifying the emissivity of the object being measured is the first step to ensure accurate readings from the infrared thermometer. The most common method is to consult the emissivity reference values provided in authoritative materials, but these values are often measured under specific conditions and may differ from actual usage scenarios. Another method is through comparison, that is, using a contact thermometer to accurately measure the surface temperature of the object, and then adjusting the emissivity setting of the infrared thermometer until the two readings are consistent. Some high-end infrared thermometers are also equipped with a visual calibration function, allowing users to quickly adjust parameters on site.
How Does Surface Treatment Improve Emissivity?
In order to improve the accuracy of infrared temperature measurement, the surface of the object is sometimes treated. For example, for a bright metal surface with low emissivity, a layer of high-emissivity black paint or a special temperature measurement sticker can be applied to the measurement area to improve its infrared radiation capability and make it easier for the thermometer to obtain the true temperature. In addition, keeping the surface clean and preventing interference from oil and oxide layers will also help stabilize the emissivity. Through these methods, the measurement effect can be optimized without changing the object itself.
