Alternative Model‐Independent Inversion Programme for Malvern Particle Sizer

Abstract The Malvern Particle Sizer, developed in 1977, is used extensively for measuring the size distribution of solid particles and drops. It has several modes of operation based on a priori assumption of a particle size distribution function and a so‐called “model independent” programme in which no prior assumptions are made about the nature of the size distribution. Unfortunately neither the developers nor the manufacturers of the instrument have revealed the algorithm which is used to obtain the particle size distribution from the light scattering data. A number of people who have attempted to verify the performance of the instrument using the model‐independent programme have encountered discrepancies which cannot be explained without knowing the details of the Malvern inversion algorithm. The results obtained in this paper show that the light scattering data recorded, using the hardware of the Malvern instrument, can be successfully processed using Shifrin's inversion technique in order to the obtain particle size distribution. The use of Shifrin's inversion algorithm, which is described fully in the open literature, has a number of advantages over Malvern's proprietary software in the context of particle sizing research. It provides the research worker with a simple and mathematically elegant alternative method of processing the light scattering data which is particularly suitable for investigating the limits of applicability of the Fraunhofer diffraction particle‐sizing technique.