Electrical zone sensing distribution

Different methods are available for the determination of the particle-size distribution of powdered solids [30]. These are optical microscopy (usually combined with image analysis), sieve analysis, laser light scattering of suspended particles, and electrical zone sensing. 

Having defined the relevant particle size the frequency of occurrence of each size can be found. Number distributions can be determined by microscopy, electrical and light sensing zone methods surface... 

II ASTM E 1772-95(1995) (1997), Particle size distribution of chromatography media by electrical sensing zone technique, 450... 

British Standard BS3405 Part 5,(1983), Determination of Particle Size Distributions, Recommendations for the Electrical Sensing Zone Method, The Coulter Principle, 450, 462, 463... 

ISO 13319 Determination of particle size distributions - Electrical sensing zone method, 450... 

Multiple techniques can be used to measure the particle size distribution, for example electrozone sensing, sedimentation, laser diffraction, and microscopy. With the exception of microscopy, they all require calibration and the results depend on the technique. For example, in a round-robin study reported in Reference 4, the commonly used electrical sensing zone technique (Coulter Counter) was compared to microscopy and sedimentation. The average particle size determined by the electrical sensing zone method was by about 25%... 

BS ISO 13319, Determination of Particle Size Distributions - Electrical Sensing Zone Method, 2000. 

The effect of particle shape on particle size distribution was investigated by Naito et al. (1998) with commercial particle size analyzers based on five different measuring principles electrical sensing zone, laser diffraction and scattering, x-ray sedimentation, photosedimentation, and light attenuation. The particles used are blocky aluminum oxide and barium titanate particles, flaky boron nitride particles, and rodlike silicon whisker ceramic powders. Altogether, four commer-... 

If the particle size distributions are characterized by the average diameters at the cumulative masses of 10, 50, and 90%, the data scattering measured by different techniques can be represented by the diameter ratios at the cumulative masses of 10, 50, and 90%, or DRio, DR50, and DR90. Since the particle diameter measured by the electrical sensing zone technique is to be the equivalent volume diameter and is independent of the particle shape, its particle diameter is defined to be one. The particle diameters measured by other techniques are then ratioed with this diameter. The experimental results of DRjo, DR50, and DR90 are summarized in Table 5. It can be seen that the results of particle analysis from different techniques can be quite different. 

The Coulter Counter, through its various models, has become an estabi ished and we I I evaluated method of counting and sizing particles. The Coulter principle, or better, the electrical sensing zone method, has been the subject of many publications, including textbooks and the British Standard 3406. The main advantage of this method is that it yields directly a number distribution of the equivalent volume diameter. 

One question which then arises is, What do the various particle analyzers measure From the electrical sensing zone technique, we get a number distribution, in spite of the fact that the method measures the volume of the individual particles. Prom the particle volume the instrument computes a volume equivalent particle diameter (see Chap. 2). The instrument then counts and reports the particles within a series of narrow (volume equivalent) diameter ranges. 

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