How to choose a proper obscuration range?

In laser diffraction particle size analysis, inaccurate results can be caused by particles agglomerating in the suspension, especially when they are fine. Therefore, a full dispersion of the sample prior to measurement is essential.

Samples that either dissolve or agglomerate in a wet medium or react with the medium are usually analyzed using the dry dispersion method.

Obscuration refers to the proportion of light scattered and absorbed by the particles in the measurement zone, which indicates the concentration of the suspension.

A background measurement has to be made prior to sample analysis. The background measurement is made up of both optical and electrical signals.

The refractive index describes the degree to which light rays are bent as they pass from one medium to another. The absorption coefficient is a measure of the light beam penetration through a material.

The reasons for abnormal background signals vary. The exclusion of abnormal background signals should begin with inspecting the sample cell, then the laser source and lens, and finally, the alignment system.