It is very difficult to directly measure the effective emissivity of a blackbody cavity, which is generally calculated by the indirect methods. Different calculation methods have certain differences. In this paper, the STEEP software, TRACEPRO software and approximation formula are used to calculate the effective emissivity of the blackbody cavity for the three commonly used blackbody models of integrating sphere, cylindrical and cylindrical-conical, and Compare the results of emissivity greater than 0.99. The results show that the consistency of the results of the three methods in calculating the cylindrical type and the integrating sphere type blackbody can be better than 0.03%. When calculating the conical black body, the difference between the results of the approximate formula and the other two schemes is less than 0.07%. The calculation results of the scheme tend to be consistent with the increase of the emissivity of the model.
To realize spectral diffuse reflectance scale in mid-infrared waveband in 0/d geometric condition at National Institute of Metrology in China (NIM), a facility based on auxiliary integrating sphere method has been built up. An integrating sphere (diameter 100mm) coated with gold and series of gold plate were used for calculating the reflectance. The uncertainty of spectral diffuse reflectance in NIM is approximately less than 3.0% (k = 2) in 3μm -14μm.