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The TOT method of particle size analysis determines the size of a particle by measuring the length of time a focused beam moving with a constant velocity spends traversing the particle. This method yields the particle size distribution as the chord length distribution (CLD). The location at which the beam transects the particle is random. Hence, the half-width of the CDL is non-zero even for a population of identical spheres, as in that case the chord length can range from 0 to the sphere diameter.
This method is implemented in a number of commercially available particle counters such as Galai counters (Galai Productions Ltd., Midgal Haemek, Israel) and Lasentec counters (Mettler-Toledo Inc.).
The Galai instruments have a transmission configuration. Details of the measurement principles of these instruments are discussed, for example, by Weiner et al (1998). See also Reproducibility of a Galai particle counter.
The Lasentec instruments work in backscattering configuration. This latter configuration, referred to as the focused beam reflectance measurement (FBRM), permits analyses of concentrated suspensions because the beam pathlength in suspension can be very small (a fraction of 1 mm).
| CITATION: Jonasz M. 2006. PSD measurement by time-of-transition (TOT) method: Introduction (www.tpdsci.com/Tpc/TOT.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 18-Jan-2006 Modified: 05-Jul-2006 Peer-reviewed: PENDING |
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