The size of the particles is called "grain size", also known as "particle size" or "diameter". When a certain physical property or physical behavior of the measured particle is closest to a homogeneous sphere (or combination) of a certain diameter, the diameter (or combination) of the sphere is taken as the equivalent particle size (or particle size distribution) of the measured particle. Of course, for non-spherical particles, the particle size is related to the measurement basis and statistical method, and the particle size can only be "equivalent.

The percentage (or cumulative percentage) of particles with different particle size intervals to the total powder is called frequency particle size distribution (or cumulative particle size distribution), and its ordinate is the particle size composition calculated on different bases, which can be the percentage or cumulative percentage of number, length, area and volume, and its abscissa is the particle size value calculated on different bases. D10,D50,D90 can reflect the uniformity of the powder, also known as the cumulative distribution of the powder.

D50: also known as the median particle size, refers to the cumulative distribution of 50% of the corresponding particle size value. This is a typical value representing the size of the particle size, which accurately divides the population into two equal parts, that is to say that 50% of the particles have a size above this value and 50% of the particles have a size below this value. If a sample has D50 = 5 μm, it means that particles having a particle diameter of more than 5 μm account for 50%, and particles having a particle diameter of less than 5 μm also account for 50%, among all particles having a particle diameter constituting the sample. D50 is often used to represent the average particle size of the powder. D90: refers to the particle size distribution, from small to large cumulative distribution percentage reaches 90% of the corresponding particle size value. That is, in a certain powder, the number of particles with particle size less than D97 accounts for 97% of the total number of particles. It is usually used to represent the coarse end particle size index of powder, which is a key indicator in powder production and application. Similarly, some industries use D95, D97 equivalent, its physical meaning is similar to D90. D10: means that the cumulative percentage below this value is 10%, as opposed to D90. In the application of production and life, these three parameters have very important significance. For example, in the pharmaceutical industry, if you know the particle size distribution of a certain drug, you can understand the effectiveness and side effects of the drug. In addition, in the field of environmental protection, particle size distribution is also one of the important indicators of air and water quality monitoring. In short, D10, D50, and D90 are three very important parameters in the particle size distribution, and they represent the particle distribution in different intervals. Tiny particulate matter is widely used in daily life and industrial production. The size and distribution of the size are directly related to the industrial process, product quality, energy consumption and safety of the production process. Therefore, it is of great significance to accurately and conveniently measure the sum diameter (particle size) of tiny particles and obtain the particle size distribution function.