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Real-time techniques for aerodynamic size measurement.

Baron-PA; Mazumder-MK; Cheng-Y-S; Peters-TM
Aerosol Measurement: Principles, Techniques, and Applications, Third Edition. Kulkarni P, Baron PA, Willeke K, eds., Hoboken, NJ: John Wiley and Sons, Inc, 2011 Jan; :313-338
As discussed in the previous chapter, optical particle counting techniques, based on light scattering, have the advantage of rapid, continuous, and nondestructive particle detection. However, the amount of light scattered may not be directly related to a specific property, such as aerodynamic particle size, that one wishes to measure. By combining the advantages of optical detection with the manipulation of particle motion, several instruments have been developed that detect more specific properties, such as aerodynamic size, of aerosol particles. The aerodynamic size of particles is used to describe their behavior in gravitational settling, filtration, respiratory deposition, sampling, and other aerosol systems. Measurement of aerodynamic size at one time could only be achieved by manually observing settling velocity of individual particles. Subsequently, impactors allowed the measurement of size distributions on a routine basis, although gravimetric and/or chemical analysis still had to be carried out in the laboratory. With the advent of new technology (e.g., lasers and microcomputers), real-time measurements became possible. Several instruments were developed to measure aerodynamic size as rapidly and accurately as possible. These included the Electric-Single Particle Aerodynamic Relaxation Time Analyzer (ESPART; HOS)2, the Aerodynamic Particle Sizerw (APS; TSI) and the Aerosizerw (TSI). While these latter two instruments allow rapid determination of size distributions, they measure particle behavior largely outside the Stokes regime and the recorded size must be corrected to give an accurate aerodynamic size of individual particles. While the aerodynamic diameter describes the inertial properties, the electrostatic charge influences the electrodynamic behavior of the charged particles in transport processes. Both aerodynamic diameter and electrostatic charge measurements on individual particles are needed in many processes; some examples are electrophotography and laser printing, electrostatic powder coating, electrostatic precipitation, electrostatically enhanced fabric filtration, and electrostatic beneficiation of minerals and coal. The ESPART is capable of measuring particle charge as well as aerodynamic diameter. These sophisticated instruments provide more specific data about aerosols; however, because of the complexity of their detection and analysis systems, they may also have various limitations and subtle problems associated with the interpretation of the data. The following sections present a discussion of these instruments.
Aerosol-particles; Aerosols; Aerosol-sampling; Airborne-particles; Electrophysiological-measurements; Electrophysiology; Filter-materials; Filtration; Lung-irritants; Measurement-equipment; Microscopic-analysis; Nanotechnology; Particle-aerodynamics; Particle-counters; Particulate-dust; Particulates; Particulate-sampling-methods
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Kulkarni-P; Baron-PA; Willeke-K
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Aerosol Measurement: Principles, Techniques, and Applications, Third Edition