Optical particle counters show a maximum measurable aerosol

concentration due to their operating principle. If this limit is exceeded

major measurement errors cannot be excluded, for example because of

coincidence. In case of testing of laminar flow boxes or clean rooms

according to VDI 2083 measurements of high upstream concentrations

are stipulated. Conventional clean room particle counters are unable to

measure at such high concentrations.

By placing the dilution system HDS 561 before the particle counter the

aerosol concentration can be reduced by a factor selected by the user.

Thus, the required upstream concentration of more than 106

 particles per

cubic foot can be diluted to a concentration which is within the measuring

range of the particle counter.

The High Dilution System HDS 561 is designed to dilute aerosols with an

adjustable dilution factor. Due to its accuracy a high degree of

reproducibility is guaranteed. The adjusted dilution factor is shown on the

display.

For a certain dilution factor the appropriate number of particles is

removed from the aerosol without occurring change in the particle size

distribution.

The device is easy and safe to operate. It is flexible to use and can be

utilised in combination with different particle counters.

The dilution system HDS is designed for a specific volume flow from

2.8 l/min to 100 l/min. Each device is calibrated by the manufacturer for a

fix flow rate. The range of adjustment of the dilution factor depends on

the current total volume flow and capillary type. For example, for a

volume flow of 28.3 l/min (1 cf/min) dilution factors from 6000 to 100000

can be adjusted (for more details see chapter “Options”).