METHOD OF AND APPARATUS FOR DETERMINING THE PARTICLE SIZE DISTRIBUTION OF A SUSPENSION OF PARTICLES

摘要

1528845 Determining particle size distribution COMPAGNIE INDUSTRIELLE DES LASERS 30 Jan 1976 [4 Feb 1975] 03869/76 Heading G1A To determine the size distribution of particles suspended in a liquid 24 the liquid is circulated through a receptacle 9 of sufficiently small crosssection for the particles to pass one at a time through a laser beam which forms a diffraction pattern in a focal plane 11, while a photo-multiplier 15 receives light from the pattern via an aperture 13, see Fig. 2 and a counter 18 counts the number of output signals of the multiplier whose amplitude exceed a threshold value set on device 19, the counting being repeated for different threshold values while a predetermined quantity of liquid circulates through the receptacle 9. The radii R 1 , R 2 of the aperture 13 are adjusted to be equal to the limits e.g. 33, 34, Fig. 3, between which, for the maximum diameter particles e.g. 8 microns, the percentage light energy within a diffraction circle of radius R increases linearly with R. The first threshold value is then set to correspond to the noise signal at the photo-multiplier with this aperture and subsequent counts are performed with higher threshold values. To count particles giving signals smaller than the above first threshold value a smaller aperture is used which lowers the noise signal and the procedure repeated. Calibration of the apparatus is carried out by circulating suspensions of particles all of the same known size and measuring the amplitude of the photo-multiplier output signal on an oscillograph 35.