WF20x

As Structure Picture shown, there are 2 micrometers in the microscope:
--Fixed Micrometer With Main Scale In Eyepiece : 0~8mm 
--Moving Micrometer With Corss & Double Lines, Moved By Measuring Knob

The Fixed Micrometer has a main scale 0~8mm length, which is used to fix the measurement position. When you turn the Measuring Knob, it will move the Moving Micrometer and show its moving distance on the knob by 0.01mm division. Keep record of its moving distance, it will be the length you need to measure.

Measuring Diameter Of Power Particle (See Picture) 
1. Put the microscope on the surface of objects, turn on the LED light. 
2, Adjust eyepiece (2) to see both micrometer clearly in view field. 
3. Adjust focusing ring (7) to see objects clearly in view field.
4. Fix the focusing by screw (9).
5. Turn Measuring Knob to move the micrometer, until the cross center locate on left side of the particle. Read out the main scale as 5 and measuring knob scale as 0.36 (a). (Left Picture) 
6. Turn Measuring Knob to move the micrometer, locate the cross center on right side of the particle. Read out the main scale as 4 and measuring knob scale as 0.51 (b). (Right Picture) 
7. Moving distance (Y) is the difference between (a) and (b) divided by objective magnification (X) : Y=(b-a)/X. 
8. Measured Diameter = Moving Distance = (5.36mm-4.51mm)/1X=0.85mm