Part II: Measuring the Size of a Specimen Using the Mechanical Stage Technique Measuring the Size of a Specimen Using the Mechanical Stage Technique Measuring Techniques D2

Preface: Before beginning this module, you should be familiar with the parts, use, and care of the compound microscope. 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. If you are unsure about the microscope’s operation, please review the Use of the Microscope module.Use of the MicroscopeUse of the Microscope Mishandling of the microscope can lead to damage of the instrument. Mishandling of the microscope can lead to damage of the instrument. Preface:

Module Requirements: To complete this module, the following equipment will be provided to you by an SLC assistant. -microscope workstation -prepared microscope slide -vernier caliper -worksheet If materials are missing or you are having problems getting started, please ask one of the SLC staff for help.

Notes: The Mechanical Stage method of measuring a specimen makes use of the scales found on the stage of the microscope. This technique has a precision of +/- 0.1mm regardless of the objective lens being used. For this reason, this technique is only suitable for measuring microorganisms that are 1.0 mm or greater.

To illustrate how to read the scale on the microscope’s stage, we’ll use an instrument called a vernier caliper. To illustrate how to read the scale on the microscope’s stage, we’ll use an instrument called a vernier caliper.

Notes: The microscope stage uses a metric scale, for that reason we will only be concerned with the metric portion of your caliper. Frequently, manufacturers design calipers with both standard and metric scales. Inspect the caliper you were provided with to find its metric increments. If you cannot find the metric portion, consult a Science Learning Center associate.

Use of the Caliper Notice with your calipers closed, the vernier scale aligns with the zero on the main scale. The zero line is called the index. Notice with your calipers closed, the vernier scale aligns with the zero on the main scale. The zero line is called the index. When measuring an object, its size in millimeters can be determined by reading the number on the main scale that is on or just to the left of the index. When measuring an object, its size in millimeters can be determined by reading the number on the main scale that is on or just to the left of the index. In this case, the index is just to the left of the 20mm mark. So 19mm is our first measurement. Index Main scale

Use of the Caliper The decimal place is found by matching up a division on the vernier scale which lines up with a division on the main scale. Here we can see that the 7 th vernier division aligns with the 26mm division of the main scale. Therefore, the diameter of this pin equals 19.7mm. Vernier divisions

Use of the Caliper Here are two more examples. Determine the size of each object.

Use of the Caliper The diameter of the penny is 19.1mm The diameter of the penny is 19.1mm The diameter of the MM is 13.7mm The diameter of the MM is 13.7mm If your answers are correct, please continue this module. If you are unsure about your answers please ask an assistant for help.

Use of the Mechanical Stage The scales on the mechanical stage are used in the same manner as the vernier caliper. Here is an example how to find a measurement using the mechanical stage. The scales on the mechanical stage are used in the same manner as the vernier caliper. Here is an example how to find a measurement using the mechanical stage. 1. Line up one edge of the specimen with a convenient reference point. The edge of the field of view may be used as your reference. 2. Place the specimen on the stage, and focus using the 10X objective.

Use of the Mechanical Stage 3. Record the initial reading. Read it the same way you read the main scale and vernier scale on the vernier caliper. The reading will be in millimeters.Your readings will be taken using the scales located at the top, or right side of the stage. The initial reading was at 50.6mm.

Use of the Mechanical Stage 4. Move the stage until the opposite edge of the specimen lines up with your same reference point. 5. Record the final reading on the main scale along with the vernier measurement. The final reading was at 60.3mm

Use of the Mechanical Stage 6. Calculate the length of the specimen. The difference between the final and the initial readings represent the length of the specimen in millimeters. Example: 60.3mm – 50.6mm = 9.7mm Note: If your answer is negative, take the absolute value of that number. Note: If your answer is negative, take the absolute value of that number.

Try It! Use the stage scales to measure the length of the specimen on the slide provided with this module. Use the stage scales to measure the length of the specimen on the slide provided with this module. 1. Line up one edge of your specimen with a convenient reference point. The edge of your field of view may be used as your reference. 2. Place the prepared slide on the stage, and focus using the 10X objective. 3. Record the initial reading. Read it the same way you read the main scale and vernier scale on the vernier caliper. The reading will be in millimeters.Your reading will be taken using the scales located at the top, or right side of the stage. 4. Move the stage until the opposite edge of the specimen lines up with your same reference point. 5. Record the second reading on the main scale along with the vernier measurement. 6. Calculate the length of the specimen. The difference between the final and the initial readings represent the length of the specimen in millimeters.

Module Completed! Please return to the main desk to obtain a post test from your friendly Science Learning Center personnel. Please return to the main desk to obtain a post test from your friendly Science Learning Center personnel.