In this reticle the circle areas double progressively, hence the diameters alter by Root 2, so that the size classes can form a continuation of the standard series of sieves for particle sizing. Each particle is assigned to a size class defined by two adjacent circles which represent the size limits of that class. Thus the distribution of size is obtained in terms of the diameter of circles having the same projected area as the particles. This method will cover particles in the range 150 micron to 0.38 micron. The size distributions with respect to their number and weight are determined separately. Final results are calculated as cumulative percents. Actual size of circles and globes are nominally 560µm, 400µm, 280µm, 200µm, 149µm, 100µm and 70µm. Circle1 is defined as 1unit. Originally designed by the National Coal Board for use in coal mining.

Glass Type and Thickness

Soda Lime 1.5mm thick

Diameter Tolerance

+0/-0.1mm

Orientation

Correct reading through glass