Scales & Verniers - Key Notes

Arlo Guthrie — Mon, 20 Apr 2009 11:20:37 GMT

Current Revision posted to Revision Guide For Student Nurses - Part 2 by Arlo Guthrie on 4/20/2009 11:20:37 AM

The Vernier scale is a special position finding device for the microscope, which enables the operator to relocate a specific point of interest at a later date.
It is very important that the position of the slide label be noted.
The same microscope must be used.
The main scale has a series of lines at intervals of 1mm.
The Vernier scale has 10 lines and figures which correspond exactly to 9 divisions of the main scale.

Reading the Vernier Scale:

Observe where the zero mark on the Vernier plate meets the main North & South scale. If it falls between 2 divisions - read the lower and record (e.g. 12).
One of the Vernier lines will coincide more or less exactly with one of the lines of the main scale (all the other Vernier lines will be slightly from a main scale line). Note the number of the Vernier line which is in closest coincidence (e.g. 7).
The first reading is therefore 12.7.
Now repeat the procedure for the East & West scale.
Note the position of the label of the slide.
To find this field of view on a subsequent occasion, select the same objective, place the slide as recorded in step 5, then pre-set both scales and Verniers to the recorded figures. This should locate the specimen so that the desired field is now in view.