According to the principle, external thermometers can be divided into single-color thermometers and two-color thermometers (radiation colorimetric thermometers). For a monochromatic thermometer, when measuring temperature, the measured target area should fill the field of view of the thermometer. It is recommended that the size of the measured target exceeds 50% of the field of view. If the target size is smaller than the field of view, the background radiation energy will enter the visual and acoustic signals of the thermometer and interfere with the temperature measurement reading, causing 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.

At different distances, the effective diameter of the measurable target is different, so pay attention to the target distance when measuring small targets. The definition of the distance coefficient K of the infrared thermometer is: the ratio of the distance L of the measured target to the diameter D of the measured target, that is, K=L/D.

1. Infrared thermometers are generally graduated according to black bodies (emissivity ε=1.00), but in fact, the emissivity of substances is less than 1.00. Therefore, when the true temperature of the target needs to be measured, the emissivity value must be set. The emissivity of a substance can be found in the "Data on the Emissivity of Objects in Radiation Thermometry".

2. Infrared thermometers cannot measure temperature through glass. Glass has very special reflection and transmission characteristics and does not allow infrared temperature readings. But the temperature can be measured through the infrared window. It is best not to use infrared thermometers for temperature measurement on bright or polished metal surfaces (stainless steel, aluminum, etc.).

1. It only measures the surface temperature, and the infrared thermometer cannot measure the internal temperature. Ambient temperature. If the thermometer is suddenly exposed to an ambient temperature difference of 20 degree or higher, allow 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 damaging the infrared thermometer, first use compressed air to remove large particles and dust, then wipe it with a cloth. Use a clean, slightly damp cloth to gently wipe the thermometer body. If necessary, dampen the cloth with a solution of water and a small amount of mild soap. In addition, when you are finished using it, please put the lens cover on the infrared thermometer as soon as possible and put it in the carrying case for storage.