CM121C Shadow Ring suitable for all ventilated Kipp & Zonen pyranometers, smart pyranometers, pygeometers and UV Radiometers to shield the instrument from direct radiation. The device allows diffuse sky irradiance measurement by covering the sensors dome with a shadow. Correction factors are supplied with the equipment to allow compensation for the diffuse radiation intercepted by the ring. The CM121C includes a factory fitted adapter to correct for the extra height of the ventilated sensors. The shadow ring requires manual adjustment every few days.