How to choose the average particle size when using?

Each particle size measurement method is to measure a certain physical property of particles under different datum, and different average results can be obtained according to a variety of different methods (such as D [4,3],D [3,2], etc.), but which average particle size should be used? Take a simple example of two spheres with diameters of 1 and 10. For the metallurgical industry, if you calculate a simple number of average particle diameters, the result is D [1,0] =(1+10)/2=5.5. But if you're interested in mass of matter, and mass is a cubic function of diameter, then a sphere of diameter 1 has a mass of 1, and a sphere of diameter 10 has a mass of 1000. In other words, the large sphere makes up 99.9% of the total mass of the system. In metallurgy, only 0.1% of the total mass is lost if a sphere with a particle size of 1 is dropped. Therefore, the simple number average can not accurately reflect the mass of the system, but D [4,3] can better reflect the average mass of particles.

In the example of the two spheres above, the mass matrix volume mean particle size is calculated as follows:

This value is a fairly adequate indication of the quality of the system ,which is important for some industries.

But in a clean room making large-scale integrated circuits, the number or concentration of particles is all that matters, because if a particle falls on a silicon chip, a defect will occur and the product may fail. A method that can directly measure the number or concentration of particles is needed. For particle counting, the number of particles is sufficient; in this case, the size of the particles is not important.