A method and an app. to improve the precision and reproducibility of particle size anal. by laser diffraction is presented. Powder particles are typically prepd. for laser diffraction testing using an ultra-​sound bath which will disperse particle agglomerates and allow a precise measurement. However, the precision and reproducibility of agglomerate dispersion is affected by ultra-​sound probe wear, corrosion and age. Differences in sonication performance can be compensated by voltage adjustments to the ultra-​sound probe, leading to substantial improvements in the precision and reproducibility of particle size detn.