Measuring Techniques D3 - PowerPoint PPT Presentation

1 / 15
About This Presentation

Measuring Techniques D3


Measuring Techniques D3 Part III: Measuring the Size of a Specimen Using a Stage Micrometer and an Ocular Micrometer Preface: Before beginning this module, you should ... – PowerPoint PPT presentation

Number of Views:133
Avg rating:3.0/5.0
Slides: 16
Provided by: RuthD152


Transcript and Presenter's Notes

Title: Measuring Techniques D3

Measuring TechniquesD3
  • Part III
  • Measuring the Size of a Specimen Using a Stage
    Micrometer and an Ocular Micrometer

  • Before beginning this module, you should be
    familiar with the parts, use, and care of the
    compound microscope.
  • If you are unsure about the microscopes
    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 with ocular micrometer
  • -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.

  • The Stage and Ocular Micrometer Technique is the
    most precise method used for measuring
    microscopic specimens here at the Science
    Learning Center.
  • An ocular micrometer consists of an ocular lens
    with equal space gradations that, unlike the
    stage micrometer, have no units.
  • Look into the microscope at your workstation to
    make sure you see the ocular micrometer. If you
    dont see the micrometer, contact a Student

  • If you have completed module D1, you should be
    familiar with the stage micrometer. The modules
    here at the Science Learning Center use a 2mm
    micrometer. In lab situations though, always
    check the label for the calibration.

  • Position the stage micrometer on the
    microscopes 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.

  • Though stage micrometers are very accurate, we
    cannot place both a specimen on a slide and the
    micrometer under the microscope at the same time.
  • To solve this dilemma, we can make use of the
    ocular scale. Its important to remember that
    the ocular micrometer divisions have no units,
    and that each division will change with each
    magnification. Therefore, you must calibrate the
    ocular scale before you can use it.

  • To calibrate the ocular scale, use the stage
    micrometer. Your calibration will determine how
    many millimeters are represented by one division
    on the ocular scale, or one ocular division.
  • If you find that one ocular division equals
    0.3mm, then you know two divisions equal 0.6mm
    and so forth.
  • Therefore, if you find a specimen covers three
    ocular divisions, you will know that it measures
    0.9mm in length.

  • With the stage micrometer in focus, rotate the
    eyepiece until the ocular micrometer aligns with
    the stage micrometer.

This example shows that one ocular division (od)
equals 0.1mm.
  • Using the ocular division from our last slide,
    we can measure the size of this animal. Based on
    what you have learned, can you figure out its

  • This animal occupies 3.4 ocular divisions.
    We found that 1 od is equal to 0.1 mm. So the
    size of this animal is 0.34mm.
  • The simple equation can be written as
  • ( of ocular divisions) x ( of mm per division)
  • diameter of cell in mm

  • The last slide gave a quick example. Do not
    take for granted that all ocular micrometers are
    calibrated the same. Always calibrate your
    instrument before making your measurements.

  • Suppose your microscope had an ocular lens
    where one division equaled 0.02mm. You found
    that your specimen covers 3 ocular divisions.
    What is the length of your specimen?
  • (3) x (0.02mm) 0.06mm

Try it!
  • Follow the procedure with the practice slides
    provided. Remember its good practice to
    calibrate your microscope for each specimen.

Module Completed!
  • Please return to the main desk to obtain a post
    test from your friendly Science Learning Center
Write a Comment
User Comments (0)