The Self-Adjusting Dilution System DIL 540 is used to defined and reproducible adjustment of the aerosol particle concentration (dilution). It is particularly useful for the verification of the test aerosol for testing cleanroom installations. In the standard EN ISO 14644-3, this is included as a requirement.
A partial stream is extracted from the raw aerosol flow. The particle concentration in the partial flow (capillary volume flow) will remain unchanged. A HEPA filter is used for separation of particles from the by-pass flow. The two flows are recombined. Dilution results from the ratio of the total flow to the capillary volume flow. The fluidic design of the device ensures isokinetic sampling at the inlet of the capillary. Interferences of particle size distribution of the aerosol through diluting are therefore minimal.
Optical particle counters have inherently a maximum measurable particle concentration. If this is exceeded, errors are to be expected for reasons of coincidence in the measurement volume of the counter. By placing the dilution system DIL 540 upstream of the particle counter, the aerosol concentration can be reduced by a factor of 100.