Walton and Beckett Graticules for Asbestos - G22, G24, G25

The Walton and Beckett graticule is used for counting fibrous dust (e.g. asbestos or glass fibers) and is particularly useful where the majority of fibers to be counted are shorter than 5 microns. The circle is divided into four by two diametrical lines scaled in units of 5 and 3 microns respectively. 3 and 5 microns are the critical measurements of fiber lengths and diameters used in fiber counting. Unlike the usual globes of other particle graticules, the Walton and Beckett has a series of shapes to compare objects with. These shapes have been designed for comparison with fibers, especially since they incorporate an aspect ratio of 3:1 or 5:1 essential for such analysis.

Reference: W. H. Walton and S. T. Beckett. Occupational Hygiene. Vol.20,pp19-23
“A Microscope Eyepiece For The Evaluation of Fibrous Dusts.”

Please Note: Calibration factors are required for each of these graticules. See note below.

G22 Walton & Beckett for asbestos

G22 Walton & Beckett for asbestos,

         3:1 ratio.  Glass Sandwich

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G24 Walton & Beckett for asbestos

Based on the G22, the G24 is produced to a new design by the Institute of Occupational Health

G24 Walton & Beckett for asbestos, 5:1 ratio.  Glass Sandwich.

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G25 Walton & Beckett for asbestos, (1996).

G25 Walton & Beckett for asbestos,

(1996).  Glass Sandwich

Important Note:

The circle on these Walton & Beckett graticules must represent 100 microns at the stage and each one must be manufactured to suit the individual instrument. Therefore, the following details should be provided with your order :

1. Calibration factor ( if known)

                 or all of the following

1. Objective magnification

2. Eyepiece magnification

3. Diameter of graticules disc required

4. Microscope make and model

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