Infrared thermometer measurement inaccuracy reasons
I. The relationship between the size of the temperature measurement target and the temperature measurement distance
External pyrometer can be divided into monochrome pyrometer and two-color pyrometer (radiation colorimetric pyrometer) according to the principle. For single-color pyrometer, in the temperature measurement, the measured target area should be filled with pyrometer field of view. It is recommended that the target size exceeds 50% of the field of view size. If the target size is smaller than the field of view, the background radiant energy will enter the pyrometer's visual acoustic signature and interfere with the temperature reading, resulting in an error. On the contrary, if the target is larger than the field of view of the pyrometer, the pyrometer will not be affected by the background outside the measurement area.
At different distances, the effective diameter of the target can be measured is different, and thus in the measurement of small targets to pay attention to the target distance. Infrared thermometer distance coefficient K is defined as: the measured target distance L and the measured target diameter D ratio, that is, K = L / D.
Second, the choice of the measured substance emissivity
1, infrared thermometer are generally black body (emissivity ε = 1.00) graduation, and in fact, the emissivity of the substance are less than 1.00. Therefore, in the need to measure the true temperature of the target, the emissivity value must be set. Substance emissivity can be found from the "radiation thermometry in the emissivity of the object in the data".
2, infrared thermometer can not be through the glass for temperature measurement, glass has a very special reflection and transmission characteristics, does not allow infrared temperature readings. However, the temperature can be measured through the infrared window. Infrared thermometer zui good not be used for bright or polished metal surface temperature measurement (stainless steel, aluminum, etc.).
Third, the measurement of the target in the bright background
If the measured target has a bright background light (especially by the sun or a strong lamp), the accuracy of the measurement will be affected, so available objects to block the target of direct light to eliminate the background light interference.
Other reasons
1, only the surface temperature measurement, infrared thermometer can not measure the internal temperature. Ambient temperature, if the pyrometer is suddenly exposed to ambient temperature difference of 20 ℃ or higher, allowing the instrument to adjust to the new ambient temperature within 20 minutes.
2, steam, dust, smoke, etc.. It blocks the optical system of the instrument and affects temperature measurement. To avoid damage to the infrared thermometer, first use compressed air to remove large particles and dust, and then wipe with a piece of cloth. Gently wipe the pyrometer body with a clean, slightly damp cloth. If necessary, dampen the cloth with a solution of water and a small amount of mild soap. Also, as soon as you are finished using the thermometer, close the lens cap and store it in the carrying case.
