Graticules, Stage Micrometers, and Calibration Standards Eyepiece Graticules (continued)


D. Particle Sizing and Distributing


The use of the eyepiece graticules showed in this section make 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


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 4.5mm x 2.025mm. Circle sizes in microns are 450, 360, 270, 225,180,145, 110, 74, 37, and 18.


Pattern NG1


Description


Paterson globes/circles. Surface chrome image.


Porton — NG2


The circle areas of the Porton graticules 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 4.5mm x .25mm. 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.


Pattern NG2


Description


Original Porton globes/circles. Surface chrome image.


New Porton — NG12


The NG12 is particularly useful since the array of globes and circles are conveniently close to where the particles pass. At the end of each band of the sample the mechanical stage is traversed vertically to take in the next band until the whole sample has been covered.


Pattern NG12


Description Dia.


Modified Porton pattern globes/circles. 16mm Surface chrome image.


19mm 21mm


24


Electron Microscopy Sciences In PA: (215) 412-8400 • Toll-Free (800) 523-5874 Fax (215) 412-8450 or 8452 • email: info@emsdiasum.com


Cat.#


68032-16 68032-19 68032-21


Dia.


16mm 19mm 21mm


Cat.#


68024-16 68024-19 68024-21


Dia.


16mm 19mm 21mm


Cat.#


68031-16 68031-19 68031-21


or stacie@ems-secure.com • www.emsdiasu m.com


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