In temperature measurement, the two-color pyrometer does not change with the surface state of the object (different surface roughness, or the chemical state of the surface is different), and does not affect the accuracy of temperature measurement, while the single-color pyrometer will be affected.

The optical part of the pyrometer, such as glass, will leave some dust after a period of use, and the presence of water, gas, oil, etc. in the air will reduce the emissivity coefficient, so the temperature measured by the monochrome pyrometer is often used. will decrease. The two-color pyrometer measures the ratio of an object in two specific wavebands. When the dust, water vapor and other substances in the two wavebands change, the measured signal drops at the same time. After division, the ratio remains unchanged. But this does not mean that the use of the two-color pyrometer does not require maintenance. When the dust, moisture, etc. are too dirty, the glass needs to be wiped.
Monochromatic pyrometers cannot measure objects smaller than the viewing range. If the target does not fill the field of view, the measurement temperature is lowered. A two-color thermometer can measure objects with a small field of view.