A method of measuring particle size of iron powder by light microscopy

Since the optical microscope working with reflected light can only measure the particle size larger than 5 microns, the particle size analysis generally adopts the microscope working with transmitted light. To calculate particle size, a microscale is fitted to the eyepiece of the microscope, which should be calibrated before use.
There are three kinds of microscales commonly used for analysis:
(1) linear scale with crosshair;
(2) Network microscopic scale;
(3) Pattern microscopic scale.