What to do if the infrared thermometer measures inaccurately
Infrared thermometers are not accurate in measuring reflective objects because they reflect. After reflection, the infrared thermometer not only measures the infrared radiation of the target, but also measures other infrared radiation energy such as the reflected surface, ambient temperature, and even sunlight sensed by the thermometer, so it may be inaccurate.
According to the principle, external thermometers can be divided into monochrome thermometers and two-color thermometers (radiation colorimetric thermometers). For monochrome thermometers, when measuring temperature, the target area should be filled with the thermometer's field of view. It is recommended that the size of the target being measured should exceed 50% of the field of view. If the target size is smaller than the field of view, background radiation energy will enter the photoacoustic branch of the thermometer, interfere with temperature measurement readings, and produce 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, that is, k=l/d.
What are the reasons for inaccurate measurement of infrared thermometers?
Select the emissivity of the tested substance
1. Infrared thermometers generally use a blackbody scale (emissivity=1.00), but in reality, the emissivity of a substance is less than 1.00. Therefore, when measuring the true temperature of a target, the emissivity value must be set. The emissivity of materials can be found in "Data on Object Emissivity in Radiation Thermometry".
2. Infrared thermometers cannot measure temperature through glass. Glass has special reflection and transmission characteristics, so infrared temperature measurement is not allowed. But temperature can be measured through an infrared window. Infrared thermometers should not be used to measure the temperature of bright or polished metal surfaces (such as stainless steel, aluminum, etc.)
Measurement of targets under strong light background
If the target being measured has bright background light (especially sunlight or strong light), it will affect the accuracy of the measurement. Therefore, objects can be used to block the strong light directly shining on the target to eliminate the interference of background light.
