用于测试建筑窗户的透光率，适用于各种材质的建筑窗户。包括天窗上部和阳台门的透过率系数和透色指数，并可同时检测玻璃幕墙的透过率系数和透色指数。

1. standard of execution
GB/T 11976-2015 外窗采光性能分级及试验方法。

2. Main technical parameters
Test items: transmittance T and color transmittance R.
The testing device consists of light source room, light source, receiving room, specimen frame and testing instrument.

Light room:
The inner surface is diffusely reflected with low spectral selectivity and a reflection ratio greater than 0.8
The illuminance on the surface of the specimen is greater than 1000lx, and the illuminance difference at each point is less than 1%
The light source room shall be rectangular, with the opening area less than 10% of the indoor surface area

light source：
Electric light source with continuous spectrum, symmetrical arrangement and light control device are adopted
The light source is powered by a stabilized voltage source, and its voltage fluctuation is no more than 0.5%
The stability of the light source was checked according to the method described in appendix 1 of jjg247-1994
The light source is specially designed to ensure that no direct light falls on the surface of the specimen

Reception room：
The inner surface is diffusely reflected with low spectral selectivity and a reflection ratio greater than 0.8
The receiving chamber is a cube, and the opening area is less than 10% of the indoor surface area

Specimen box：
The thickness of the specimen frame is equal to the actual wall thickness
The connection part between the specimen frame and the two-chamber opening is strictly sealed to ensure no light leakage

Optical receiver:
The optical receiver shall have a V() correction whose spectral response is consistent with the illumination efficiency of the international illumination commission's light vision spectrum
The optical receiver has a cosine corrector, and the optical receiver meets the requirements of the first-level illuminometer specified by JJG245
The optical receiver is uniformly arranged on the periphery and inner side of the opening of the receiving chamber, and the quantity is set according to the size