Single-Particle Optical Counter

Single-particle optical counters cannot be easily used for measuring high aerosol concentrations. Whitby and Liu (1967) have shown that if many small particles are in the illuminated sensitive volume of this type of instrument at the same time, significant errors are introduced because the particles are considered by the detector to be fewer in number and greater in size. Thus there is a practical upper limit on the aerosol concentration that can be measured by such an instrument, being on the order of 1000 to 10,000 particles per cubic centimeter. 

Single Particle Optical Counter Principle and Application, Aerosol Generation, Measurement, Sampling, andAnalysis, Ed. Liu, B. Y. H., Academic Press, New York, 1976. 

Whitby, K. T., Vomela, R. A., Response of Single Particle Optical Counters to Non-ideal Particles, >mrow. iScr. Technol, 1967, 1,801-814. 

Gebhart, L, Reponse of Single-Particle Optical Counters to Particles of Irregular Shape, Part. Part. Syst Charact, 1991,8,40-47. 

Whitby, K. T., and Willeke, K., Single Particle Optical Counters Principles and Field Use, in Lundgren, D. A. et al. (Eds.), Aerosol Measurement, University Presses of Florida, Gainesville, FL, 1979. 

Since particles in the micron and submicron size range are of primary importance, the emphasis in this study is on using the singleparticle light scattering characteristics, and a new optical single-particle ratio counter was improved and calibrated. Furthermore, an electronic data acquisition system was developed, and finally the counter was applied to an in situ, real time study of automobile exhaust gas analysis. 

PSS Accusizer 780/SPOS Single particle optical sizer consists of a patented autodilution stage, single particle optical sensor, pulse height analyzer/counter (PHA), systems computer/processor and software control. The autodiluter performs a continuous dilution of the concentrated sample... 

Fig. 18.15 Advanced methods for single particle analysis in LC ARROW chips, (a) Nanopore added to reservoir for single particle entry into LC ARROW (b) Optical dual beam particle trap based on balancing the scattering force due to counter propagating beams...

The scattering function can be determined from theory for certain important special cases. The performance of optical single-particle counters depends on the variation of the scattering function with angular position. 

Noninterfering Optical Single-Particle Counter Studies of Automobile Smoke Emissions... 

Optical single-particle counters offer much more rapid aerosol size analysis than do impaction methods. 

For the optical particle counter of Fig. 6.5, the sensing volume is 1.5 x 1.5 x mm. Determine the total energy scattered by the air molecules in the volume. Compare this with the scattering by single particles with diameters ranging from 0.05 to 5 / m and a refractive index of 1.5. Assume k = 0.5 m and express your answers in terms of the incident intensity. The temperature is 20 0,... 

Hess, C. F., Non-intrusive optical single-particle counter for measuring the size and velocity of droplets in a spray, Applied Optics, 23, 4375-4382 (1984)... 

Optical particle counters—single counter useful for only 1 decade of size requires calibration sensitive to shape and refractive index 0.3 (commercial) 0.1 (research) 3-100 >200 possible 20 useful 1 particle/L Light-scattering from single particles... 

Optical particle counters require dilution of highly concentrated particle suspensions to a concentration level below the concentration limit of the sensor. The low "overconcentration" limit of a OPC was in the past the major disadvantage, limiting the use of optical single particle counters. The main objectives of the sample delivery procedure are ... 

Figure 14.6. Approaches to optical in situ sizing of contaminant and wear particles with (a) an external counter (b) an internal counter (c) two concentric beams (d) a single beam. (From Ref. 9, with permission from CRC Press.)...

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