microorganisms are microscopic objects that are visible only with the help of a microscope. micrometry refers to the measurement of dimensions of the desired microorganisms. ocular micrometer and stage micrometer.

1. MICROMETRY
Sachu Elsa
Mathew
B.A.M College
Thuruthicad

2. • Microorganisms are microscopic objects that
are visible only with the help of a microscope.
Sometimes it is necessary to measure its
dimensions for its identification process. But
determination of the size of a microorganism
is not an easy process.

3. Micrometry:
• Micrometry refers to the measurement of
dimensions of the desired microorganisms
under a microscope which uses two micro-
scale known as micrometers. These are two
types
• Types of Micrometry: There are usually two
types of micrometers Stage micrometer.
Ocular meter or ocular micrometer

4. MICROMETRY
• Principle
Calibration of the ocular micrometer using the
stage micrometer

5. OCULAR MICROMETER
• The ocular micrometer is a glass disc with 100
equal divisions or lines on it but with no
absolute value and it is placed in the ocular of
the microscope

6. STAGE MICROMETER
• It is used to calibrate the Ocular micrometer.
• It looks like a microscope slide but has a
standard scale etched into it. The smallest
divisions are 0.01mm In length. It is just like a
tiny ruler.
• 0.01mm=10 micro m

7. MICROMETERY
• Materials
1. Light microscope
2. Ocular micrometer
3. Stage micrometer

8. PROCEDURE
• The eyepiece is removed from the microscope,
and the ocular micrometer is placed carefully into
the eyepiece. The eyepiece is placed back in the
microscope.
• The stage micrometer is clipped to the stage and
the etchings centered by moving the mechanical
stage.
• The low power objective is taken to position.
• The eyepiece is rotated till the etchings on both
the micrometers superimpose.

11. • The required objective is taken to position. The
required objective is that, using which the whole
microorganism can be viewed and it covers the
microscopic field to the maximum possible extent.
• With the required objective in position the mechanical
stage is moved, so that a line on the stage micrometer
coincides with a line on the ocular micrometer. Then,
another line is searched on the ocular micrometer,
which coincides with another line on the stage
micrometer. The number of divisions between the
coinciding lines is counted for both the micrometers.

13. • The calibration factor for the objective used is
calculated.
• The stage micrometer is removed.
• The slide containing the microbe to be observed is
placed on the stage and focused.
• The number of ocular divisions covered by the
microbe is counted by viewing through the eyepiece.
• The size of the microorganism is determined by
multiplying the number of ocular divisions covered by
the microbe with the calibration factor.

16. Application:
• This method is more important in
microbiological laboratory. The main purpose
of this method to identified the length if the
organism such as bacteria, virus, human RBC
cells, yeast cell etc..