(1) The effect of non-black body. Since the measured object is a non-absolute black body, and the blackness coefficient ελ of the object is not constant, it is related to the wavelength λ, the surface condition of the object and the temperature. The shading factor sometimes varies greatly, which adversely affects the measurement. Sometimes in order to eliminate the influence of ελ, the conditions of black body radiation can be artificially created.

(2) The influence of the intermediate medium. If there is dust, smoke, carbon dioxide and other gases between the optical pyrometer and the measured object, it will absorb thermal radiation, thus causing errors. It is difficult to control dust-free during actual measurement, so the optical pyrometer should not be too far away from the object to be measured, generally within 1~2m, and no more than 3m at most.

(3) Optical thermometers should try not to measure in places with strong reflected light, otherwise errors will occur.

(4) Pay special attention to keeping the objective lens clean and submit it for inspection on a regular basis.