Three spectrometry systems have been developed to determine the sizes and velocities of particles in the air. The spectrometers could be used for the environmental monitoring of particulate pollution, for clean-room monitoring experiments, or for other particle-counting jobs where real-time data on small particles is needed. One system is a forward-scattering spectrometer that detects particles ranging from 0.2 to 0.6 micrometers in size. Particles passing through the beam in the sampling region scatter light out of the collimated beam; and the photodetector measures this scattered light, the intensity of which is proportional to particle size. The second spectrometer images the shadows of particles passing through the sample area on the photodiode array. Particle size can be calculated by determining how many diodes are within a shadow. These two systems employ simple digital logic circuits to process the data and read them out as realtime histograms. In the third system two circuits are used. One unit covers a range of particle sizes from 0.1 to 1.5 micrometers, and the second unit covers a range from 1 to 25 micrometers.

  • Supplemental Notes:
    • This article appeared in a publication Analytical Techniques: A Compilation.
  • Corporate Authors:

    National Aeronautics and Space Administration

    400 Maryland Avenue, SW
    Washington, DC  United States  20546
  • Authors:
    • Williams, J R
    • Russell, D M
  • Publication Date: 1975-1

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Filing Info

  • Accession Number: 00128517
  • Record Type: Publication
  • Report/Paper Numbers: NASA CR-2028
  • Contract Numbers: MFS-24402, NPO-11612, MFS-16968
  • Files: TRIS
  • Created Date: Apr 21 1976 12:00AM