(1) The influence of the non-black body of the optical pyrometer. Because the measured object is a non-absolute black body, and the object's blackness coefficient ελ is not a constant, it is related to the wavelength λ, the surface condition of the object, and the temperature. The blackness coefficient sometimes varies greatly, which has a very unfavorable effect on the measurement. Sometimes in order to eliminate the influence of ελ, conditions for blackbody radiation can be created artificially.

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

(3) The optical pyrometer should try not to measure in places where the reflected light is strong, otherwise errors will occur.

(4) For the optical pyrometer, special care should be taken to keep the objective lens clean and send it for inspection regularly.