Calibration of Eyepiece Micrometer

What is meant by micromeritics?

Micromeritics is the science and technology of small particles. It involves the study of particle size and size distribution, shape, angle of repose, porosity, true volume, bulk volume, true density, and bulk density.

The unit of particle size is a micrometer (\mu m)\; or simply micron(\mu)\;, which is equal to 10-6 meters or 10-3 millimeters. The millimicron (m\mu)\; is referred to as a nanometer (nm).

The size and the surface area of particles have profound importance in. pharmacy. A few important influences of particle size are mentioned below:

  • Small particles will have a large surface area leading to faster dissolution and drug absorption.
  • Particle size and shape influence the flowability of powders. The good flow property is an important requirement for tablet and capsule manufacturing.
  • Particle size is important for the proper mixing of granules and powders.
  • The physical stability of suspension is dependent on the size of dispersed particles. The smaller the particle the slower the rate of settling (stokes’ law).

Aim: To calibrate the eyepiece micrometer.

Principle of the Eyepiece Micrometer

The eyepiece micrometer has 100 divisions. The determination of the actual length of each division is known as calibration. The calibration is done in comparison with the standard stage micrometer. The number of divisions of the eyepiece micrometer matching equally or coinciding with the number of divisions of the stage micrometer is the basis for calibration. Each division of the stage micrometer is equal to 10 \mu m

Materials and apparatus required: Microscope, eyepiece micrometer, standard stage micrometer.


  1. The eyepiece micrometer is matched with the stage micrometer in such a way that the first line of both micrometers coincides.
  2. Then it is carefully looked to find out another point where lines of two micrometers coincide.
  3. The number of divisions of the eyepiece micrometer that equals the number of divisions of the stage micrometer is worked out.

Observation and Calculation:

Number of divisions of eyepiece micrometer (X) = Number of divisions of the stage micrometer (Y);

One division of the eyepiece micrometer = Y/X number of divisions of the stage micrometer

As 1 division of stage micrometer is equal to 10 \mu m, the one division of Y eyepiece micrometer = 10\times\frac YX\;\mu m

Report: One division of eyepiece micrometer = ___________________ \mu m\;

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