Measuring Techniques
D1
Part I:
Measuring the Size of a Specimen
Using the Field of View Technique.
Preface:
Before beginning this module, you should
be familiar with the parts, use, and care of
the compound microscope.
 If you are unsure about the microscope’s
operation, please review the Use of the
Microscope module.
 Mishandling of the microscope can lead to
damage of the instrument.

Module Requirements:

To complete this module, the following equipment will be
provided to you by an SLC assistant.
-microscope workstation
-prepared microscope slide
-stage micrometer
-worksheet
If materials are missing or you are having problems getting
started, please ask one of the SLC staff for help.
Module D1: Objective
The completion of this module will allow
you to use the Field of View Technique in
order to measure length, width, diameter
and other linear dimensions of a microscope
specimen.
Of all the microscope measuring techniques
covered at the Science Learning Center, the
Field of View Technique is the least
precise.
Use the Field of View Technique only when
approximate measurement is adequate, and
the specimen’s size is 30 to 4500 microns.
Procedure:
1. Chose the objective lens that is appropriate for your
specimen. At this point, adjust your microscope,
selecting the 10X objective lens.
Turn and lock
into place
Procedure Continued:
2. Obtain a stage micrometer. The Science Learning
Center uses 2mm micrometers divided into units
of 0.01 mm.
Procedure Continued:
3. Position the stage micrometer on the microscope’s
stage and clearly focus the scale using the 10X
objective lens.
Note: If you are having trouble finding the scale at 10X, switch to a lower power,
such as 4X, to center scale. Then select the 10X objective and use the fine
adjustment to focus.
Procedure Continued:
4. Measure the diameter of the field of view.
To make your measurement, line up one end of
the stage micrometer scale with the edge of your
field of view. Adjust your microscope now.
Example
Procedure Continued:
With the micrometer lined up in your field of
view, measure the diameter to which your eye can
see within the illuminated area.
Note: At this point do not adjust your stage.


Write down your measurement on a piece of scrap
paper.
Procedure Continued:
You should have found your workstation
microscope field of view to measure in a
range between 1.66 and 2.06 mm.
 If your results are different, please go
through the procedure again.
 If problems remain, please ask an SLC
representative for assistance.

Notes:
When we measured the field of view, we
took the diameter of the “circle” that we
could see using our microscope. That
distance may vary from scope to scope due
to calibration, manufacture, and of course
human error.
 For this reason, we must include an
uncertainty with our measurement.

Calculating the Uncertainty

The uncertainty of your measurement can be given
as +/- one tenth (0.1) of the diameter of your field
of view measurement.
Example: My field of view measurement is 1.85 mm. So my uncertainty
would equal +/- 0.185.

Therefore, if the length of my specimen is
1.255mm and I have an uncertainty of 0.185. I
can say that actually the specimen measures
between 1.070 mm and 1.440 mm.
Try It!
1.
2.
3.
4.
Remove the stage micrometer.
Place your sample specimen on the stage.
Focus
Estimate the area covered by your specimen.
For example, we have drawn imaginary lines across our field of view to
show that the size of this stone is 1/3 of our field of view.
Try It!
5.
Calculate the size of the specimen by multiplying the
fraction of the field the specimen covers, times your
field of view. Don’t forget your uncertainty!
For example: Our specimen covers 1/3 of the
field of view. The initial field of view
measurement was 1.85 mm. The calculation
would be:
(0.333)x(1.85) = 0.617 mm +/- .185 mm
Important
If you change to a different objective lens,
the field of view will be different than the
measurement you have taken for the 10X
objective.
 Naturally, the field of view decreases with
greater magnification.
 Therefore, if you must change the power of
the objective lens, you must determine the
diameter of the new field of view.

Measurement Conversion
In some cases you will be required to
convert your measurements to a smaller
size.
 A useful conversion to remember is
millimeters (mm) to microns (μm).
1000 μm = 1 mm
1 μm = 0.001mm

Measurement Conversion
Let’s use our earlier example to perform a
measurement conversion. Our specimen covers ½
of the field of view. Our initial field of view
measurement was 1.85 mm. Your calculation
was.
(0.5)x(1.85mm) = .925 mm +/- .185 mm
(0.5)x(1850μm) = 925 μm +/- 1.85 μm
Note: do not forget to convert your uncertainty to get
your final answer.
Module Completed!

Please return to the main desk to obtain a
post test from your friendly Science
Learning Center personnel.