— validate equipment used to prepare secondary calibration suspensions for automatic particle counters;

— perform online secondary calibration of automatic particle counters;

— match two or more online particle counters, i.e. to count the same number of particles at a given size by two APCs associated on line;

— validate online particle counting systems with and without online dilution as used, for example, to measure the filtration efficiency of a hydraulic filter as described in the multipass filter test in ISO 16889.