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LAP 323

LAP 323 Aerosol Spectrometer for analysis of particle size distributions and particle number concentrations in aerosols, Dual Wave Length Technology

With the new single particle scattering light spectrometer LAP 323 the innovative Dual Wavelength technology of Topas GmbH for particle size and number determination is implemented.
Aerosol particle size spectrometer LAP 323 frontside
The use of two laser diodes with different wavelengths allows a high-resolution detection of even small spherical particles and their accurate classification. The application of two light sources with monochromatic light of different wavelengths for scattered light generation has the advantage to level out discontinuities i.e. that particles whose size falls within this range are difficult to distinguish from one another. Additionally, the aerosol spectrometer is characterized by integrated sampling, intelligent volume flow control and compact design. The Laser Aerosol Spectrometer LAP 323 meets all technical requirements for aerosol spectrometers as described in ISO 21501-1 and VDI guideline 3867 part 4.


ISO 21501-1
ISO 18562-2
VDI 3867-4
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  • very high classification accuracy within the particle size measurement range
  • homogeneous and high illumination intensity in the measuring volume for an optimized lower detection limit
  • avoidance of border zone error through optimized measuring cell design
  • verification of mass concentration using a removable bypass filter


  • high resolution analysis of aerosols
  • filter testing and filter characterisation
  • analysis of test, calibration and pharmaceutical aersols
  • particle size determination of sprays, oil mists, dusts and powders

The Laser Aerosol Spectrometer uses an internal pump for the suction of the sample volume flow rate into the device. The volume flow rate is divided and only a small amount is directed into the measuring cell. Two long-life laser diodes of different wavelengths are located in the measuring cell and illuminate the particles flowing by. The resulting scattered light is collected by a photo detector. The optical signals are converted into electrical signals and processed by a microprocessor. The microprocessor amplifies the signals, determines their pulse height and classifies them into the appropriate pulse height classes. The channel contents (more than 90 size channels are available) are transmitted to a computer via the serial interface. Using the software PASWin with the provided calibration function, particle sizes can be assigned to the class boundaries resulting in the particle size distribution.

Parameter title Unit Value
resolution, measurement time s ≥ 1 (variable adjustable)
measuring range, particle size µm 0,15 ... 40
measurand - particle number concentration, particle size distribution
resolution, particle size - max 128 size channels (adjustable)
test flow rate L/min 3,0 (0,1 trough measuring cell)
measuring range, concentration #/cm³ max. 10'000
power supply - 110 - 230 VAC (50 - 60 Hz); 12 VDC (4,2 A)
power consumption W 21 (normal operation)
light source -
serial interface -
dimensions (w x h x d) mm
weight kg

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Laser Aerosol Spectrometer LAP 322, front view
detail view

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