Particle Sizing and Distributing
The use of the eyepiece graticules shown in this section makes it possible to analyze specimens containing particles as an alternative, or in addition to, sieving. Graticules for particle size analysis are particularly popular when there are only limited quantities of particles or where particles are smaller than 50 microns in diameter. Typical substances analyzed are sand grains, soil particles, plant seeds, fertilizers, abrasives, liquid droplets, pigments, pulverized coal, silica, fibers, and fine dust.
The basic principle employed is to compare particles to the globes and circles of varying sizes that appear on the graticule – dark particles being compared to solids globes, and light or transparent ones to the circles. Naturally the procedure varies with the graticule concerned, more information about which is given below.
Please note that for calibration, the circles and globes will represent particles smaller in diameter by the magnification of the objective.
Paterson Globes and Circles - NG1, 21 mm
The graticule consists of a central rectangle, sub-divided into nine smaller rectangles, with a number of increasing circles outside the top and bottom horizontal edges. The marked figures are the diameters of the circles in units. 250 units represent the horizontal length of the large rectangle. Rectangle size is 4.5 mm x 2.025 mm. Circle sizes in microns are 450, 360, 270, 225, 180, 145, 110, 74, 37, and 18.