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Commercial single-particle optical counters (OPC) are typically optimized for a wide range of particle compositions as represented by the refractive index of the particles, a significant factor in determining light scattering by a particle. This optimization is achieved by measuring light scattered by the particle in the near-forward direction (for example, Holve and Self 1979). Thus, the angular range for the detection of scattered light is limited, which may result in a multivalued response of the OPC to particle size.
However, when particles to be analyzed in one run are all of the same composition, the angular range for the detection of scattered light can be significantly widened. This may limit a particle range of multivalued response or produce a univalued response of the OPC. Such an OPC is described by Kiselev et al (2005) who studied condensational growth of water droplets on salt seed particles.
That instrument features nested, optically determined sampling zones which were in order to ignore signals from particles skimming the sampling zone, not representative of the particle size. Other methods of rejecting such signals include the use of two-color illumination and detection system (Wang and Hencken 1986).
| CITATION: Jonasz M. 2006. White-light particle counters (www.tpdsci.com/Tpc/WtLtOPC.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 15-Jan-2006 Modified: 05-Jul-2006 Peer-reviewed: PENDING |
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