| Abstract: | Previous work to predict the minimum count or mass of particles to achieve a given repeatability of a size parameter has focussed on relatively narrow size distributions. Work by Masuda and Gotoh 1], based upon the log‐normal distribution by number, produce a prediction of the number of particles to be counted to achieve a defined accuracy of median volume mean MVD and mass median diameter MMD. The published paper limited the geometric standard deviations (sg) to a maximum of 1.6. This equates to a size distribution covering just less than 1 decade of size. Modern laser diffraction units have optical arrangements enabling a range of particle sizes between 0.05 microns to 2000 microns to be determined. With the laser diffraction unit in mind the predictions of Masuda and Gotoh were extended to higher values of (sg) where limitations were seen. An alternative prediction was then explored whose results compare very favourably with practical measurements of a characterised certified reference material CRM. |
