Guidelines for Ensuring the Measurement Accuracy of Infrared Thermometers
The core principle of infrared thermometer technology is based on the emitted infrared energy. The most critical factors are emissivity, field of view, distance to the spot and spot position.
Emissivity: All objects reflect, transmit and radiate energy, and only the radiated energy indicates the temperature of the object.
When an infrared thermometer measures surface temperature, the instrument receives all three types of energy. Therefore, all infrared thermometers must be adjusted to read only the radiated energy. Measurement errors are usually caused by infrared energy reflected from other light sources. Some infrared thermometers support adjustable emissivity; emissivity values for various materials can be found in published emissivity tables. Other instruments have a fixed preset emissivity of 0.95. This value applies to the surface temperature of most organic materials, paints or oxidized surfaces. For such surfaces, apply tape or matte black paint on the measured surface for compensation. When the tape or paint reaches the same temperature as the base material, measuring the temperature of the tape or painted surface gives its true temperature.
Distance-to-spot ratio: The optical system of an infrared thermometer collects energy from a circular measuring spot and focuses it onto the detector. Optical resolution is defined as the ratio of the distance from the infrared thermometer to the object and the measured spot size (D:S). The higher the ratio, the better the resolution of the infrared thermometer and the smaller the measured spot size. Laser aiming is only used to help target the measurement point.
The latest advances in infrared optics introduce near-focus capability, enabling accurate measurement of small target areas and preventing the influence of background temperature.
Field of view: Ensure the target is larger than the spot size of the infrared thermometer during measurement. The smaller the target, the closer the thermometer should be to it. When high accuracy is critical, ensure the target is at least twice the spot size.
