BS ISO 26723:2020 pdf free.Plastics – Determination of total luminous transmittance and refl ectance.
BS ISO 26723 5.1 The apparatus shall consist of a stabilized light source, an associated optical system, an integrating sphere with ports, and a photometer comprising a photo-detector, signal processor and display unit or  recorder (see Figure 1).， 5.2 The light source and the photometer shall be used in conjunction with a filter to provide an output corresponding to the photopic standard luminous efficiency V[2) (as defined in ISO/CIE 11664-1), which is identical to the colour-matching function y (2] specified in ISO/CIE 11664-1 under CIE standard illuminant D65 as specified in ISO 11664-2. The output of the photodetector shall be proportional to the incident flux, to within 1 % of the incident flux, over the range used. The spectral and photometric characteristics of the light source and photometer shall be kept constant during measurements. 5.3 The total port area (sum of area of the port a, b, C and d) shall not exceed 4,0 % of the internal reflecting area of the sphere. It is desirable for the diameter of integrating sphere to be not less than 150 mm to be big enough for a specimen to pull together the scatter light to the thickness direction of the specimen enough. 5.4 Ports a, b and C shall be centred on the same great circle of the sphere. The angle between line ac and line bc shall be 14。。Where the line ac means the line which links the centre of port C to the centre of port a, and the line bc means the line which links the centre of port b to the centre of port C. Port d shall not be in the great circle on the sphere with port a, b and C. 5.6 The white reference which is attached on the port c shall have the even high reflectance for all wavelengths of the visible ray. Barium sulfate and Polytetrafluoroethylene (PTFE) are suitable. The inner wall of the integrating sphere shall have a coating applied that has the same reflectance as a white reference.BS ISO 26723 pdf download.