DDS 560 - Aerosol Dilution System with variable dilution ratio

The Dynamic Dilution System DDS 560 is designed to definitely and reproducibly dilute aerosols according to EN ISO 14644 part 3 with possibility to adjust the dilution factor. The adjusted dilution factor is shown on a display. In the applied principle that corresponds to the standard VDI 3491-15, particles are removed from the sample according to the specified dilution ratio – the particle size distribution remains unchanged.

Optical particle counters show a maximum measurable aerosol concentration due to their operating principle. If this limit is exceeded major errors cannot be excluded, for example because of coincidence. In case of clean room testing or laminar flow box testing according to VDI 2083 measurements of high upstream concentrations are required. Conventional clean room particle counters are unable to measure at such high concentrations.
By placing the dynamic dilutor DDS 560 before a particle measuring device, e.g. the LAP 322: Laser Aerosol Particle Size Spectrometer, the aerosol concentration can be reduced by a factor selected by the user. Thus, the required upstream concentration can be diluted to a concentration which is within the measuring range of the particle counting device.

Advantages

• Various adjustable dilution factors
• Suitable for various operation flows (particle counter flows)
• Monitoring the particle counter flow rate
• Maintains gas characteristics of original aerosol
• Totally self-contained

The device is easy and safe to operate. The power supply can either be from the mains or from a battery. Thus, it is flexible to use and can be utilised in combination with different particle counters.
The dilution system is applicable for volume flows from 0.4l/min to 3l/min. The range of adjustment of the dilution ratio depends on the current total volume flow. For example, for a volume flow of 1l/min dilution factors from 10 to 370 can be adjusted.

Applications

• Checking HEPA- and ULPA-filters
• Validation and test of clean room equipment
• Filter media verification
• Aerosol research
• Verification of aerosol generators and powder disperser

Accessories

• Set of straight adapter R3 and elbow adapter R4 for aerosol outlet
• Replacement HEPA-Filter capsule

Principle

• The operating principle is based on the splitting of the total volume flow into a so-called bypass volume flow and a capillary volume flow. By means of an HEPA-filter all the particles are removed from the substantially larger bypass volume stream. The particle concentration of the smaller capillary volume stream remains unchanged. These two flows are eventually brought together again. The dilution factor is determined by the ratio of the capillary volume flow to the total volume flow. Both volume flow rates are continuously measured. The volume flow ratio is calculated and shown on the display. The total flow rate of the DDS 560 is set by the inlet volume flow of the particle counter. The user can adjust the desired dilution ratio with a control valve in the bypass line.

Specifications

• Volume flow range: 0.5…3  l/min
• Range of dilution ratios: 1:10 … 10:370 at 1 l/min (depending on overall volume flow)
• HEPA capsule:
  • Filter efficiency 99.97 % for 0.3 µm DOP droplets (according to ASTM D2986-71)
  • Guaranteed lifetime of 500h at volume flow of 3l/min with 2 x 106 particles/cm3 (<1 µm)
• Power supply: 12 V DC, 300 mA (via AC adapter)
• Dimensions (WxHxD): 300 mm x 200 mm x 140 mm
• Weight: 2.9 kg