Improving the sensitivity of forward light scattering technique to large particles

The detection of a small number of large particles whose size lies outside the required size distribution is important in the processing of many mater ials when those particles result in the deterioration of the product qualit y. Laser diffraction, which is a very popular technique for on-line monitor ing and process control, has, however, limited sensitivity to those few lar ge particles. This paper deals with the improvement of this sensitivity. Th e fluctuations of the signal received by the detectors were analyzed by bot h experiment and simulation. Two statistical approaches, crosscorrelation a nd principal component analysis (PCA), were applied. A detection procedure is proposed which is based on the combination of sweep selection through PC A and an appropriate deconvolution of the selected sweeps. The preliminary experiments with Al2O3 powder showed an improved sensitivity to the large p articles.