Measuring Cells

The eyepiece graticule and stage micrometer are used to measure the actual size of specimens.
The eyepiece graticule is a glass disc marked with 100 divisions that are calibrated using a stage micrometer.1. The stage micrometer is placed on the stage. The eyepiece graticule is placed over the eyepiece.2. The eyepiece graticule is calibrated against the very accurate stage micrometer. The eyepiece has divisions but no scale.3. The stage micrometer is a glass slide with markings. It is a very accurate scale in micrometers. One division = 1 micrometer.The specimen is then observed through the eyepiece.When observing the micrometer through the eyepiece, if it is found that 40 divisions of the eyepiece correspond to 25 micrometers then one division of the eyepiece corresponds to 0.625 micrometers.For example, if forty divisions of the eyepiece correspond to 25 micrometers then each eyepiece division is 0.625 micrometers.The micrometer stage slide is removed and the specimen slide placed on the stage. The size of the specimen can be determined by measuring it with the eyepiece.