The eyepiece scale is divided into 100 small divisions

The stage micrometer (calibration slide) scale is 1 mm divided into 100 divisions, each division is equivalent to 10µm.

Method

1. Insert the eyepiece scale (round glass disc) into the eyepiece by removing the uppermost lens and placing the scale on field stop.

2. Insert the eyepiece into the microscope.

3. Place stage micrometer on microscope stage

4. Focus low power objective on stage slide.

5. Adjust stage and eyepiece scales until eyepiece scale (numbered) lies along the single line of the stage scale.

6. Note number of eyepiece divisions and its appropriate stage measurement, e.g.

50 eyepiece divisions = 125 µm

10 eyepiece divisions = 25 µm

7. From this reading, work out value for one eyepiece division.

50 eyepiece divisions = 125 µm

eyepiece division = 125/50 µm = 2.5 µm

8. 10 eyepiece divisions = 25 µm

eyepiece division = 25/10 µm = 2.5 µm

9. Repeat for all objectives and note readings.

10. It is recommended that a separate eyepiece is kept with the micrometer disc inside. This eyepiece can then be inserted when measurement is required.

Calibration need only be done once for each microscope in use.