DENSITOMETER FOR SUSPENDED DUST

PURPOSE:To improve a mass density conversion coefficient based upon particle size dependency and to reduce the size and weight of the densitometer by arranging masks which has a couple of light transmission holes in front of and behind a condenser lens and photodetecting scattered light which is generated in the long-diameter direction of parallel luminous flux and travels forward. CONSTITUTION:The masks 23 an 25 having the couple of light transmission holes 30 and 30 are arranged in front of and behind condenser lenses 28 and 29 of the forward scattering photodetection type densitometer for suspended dust measurement. Then scattered light is generated when a collected air flow containing suspended dust passes through the parallel luminous flux 17 at an air flow cell part 8. Then a photosensor 15 photodetects only the scattered light which is generated by the couple of light transmission holes 30 and 30 in the long-diameter direction of the parallel luminous flux 17 and travels forward. Consequently, the mass density conversion coefficient based upon the grain size dependency characteristic to light scattering is improved to reduce the capacity and weight of the densitometer to half.