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.
Porton - NG2, 21 mm
The circle areas of the Porton greaticules increases with Root 2 progression, as do the divisions on the right hand side of the rectangle. These divisions are numbered for convenience. The rectangle size is 4.5 mm x .25 mm. Circle sizes in microns are 560, 400, 280, 200, 140, 100, 70, 50, and 35. The specimen is racked on the mechanical stage of the microscope and traverses are taken right across the deposit, sizing all the particles encountered.
- Original Porton globes/circles.
- Surface chrome image.