Particle Size Distributions: Dynamic Image Analysis Beats Laser Diffraction in a Micron to Millimeter Range

摘要

Laser diffraction is the most frequently used measurement technique for the analysis of particle size distributions in the range 1 micron to 1 mm in the context of quality control. Modern laser diffraction systems offer some convincing advantages such as short measurement times, easy operation and reproducible analysis results. However, they also have various disadvantages: Even if the instruments have been calibrated and validated, an absolute particle size measurement is not possible. Various round robin tests have shown that the analysis results depend strongly on the type of instrument and even on the particular model and software version. Dynamic image Processing is an established method for size and shape analysis of free flowing, dispersed particles with hundreds of customers and applications all over the world. With the help of the latest camera technology the method is now available also for particle sizes from 1 micron, to 3 mm, a size range which was previously covered exclusively by laser diffraction. The same advantages are now available for fine powders as well as for larger particles: reliable detection of over-size, high resolution and excellent reproducibility of the particle size results, information about particle shape, as well as easy operation, short measuring times, and an intuitive, simple measuring principle. Indirect methods with limited accuracy, such as laser diffraction but also complex optical methods with unreliable statistics, such as microscopy, become increasingly outdated.