What are D[4,3] and D[3,2]?

D[4,3] and D[3,2] are the mean diameters of the particle size based on volume-weighted and area-weighted mean results, respectively. Different mean diameters are used to compare results with different techniques. For example, if results from the volume-based laser diffraction method are compared, then the D[4,3] volume-weighted mean result is preferred. If, however, the measurement results emanating from an image analysis system are compared, D[3,2] area-weighted mean result is prioritized. 

The calculation of the mean diameter based on different weighting is shown below:

For example, two spheres are available, whose diameters are 1μm and 10μm, respectively. If the number-weighted mean diameter is required, then the number-weighted mean diameter is:

In this case, the mean diameter shows the quantitative relationship that corresponds to number-weighted.

Suppose the mean diameter of the system needs to be systematically reflected. In that case, the volume-weighted mean diameter shown below should be applied, which indicates that the volume of the large particle has occupied more than 99.9% of the system volume.

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