Using Vernier Calipers

Introduction Vernier Calipers are a valuable measuring tool that enable us to increase our degree of precision when measuring the size of objects. However, learning to read callipers can be somewhat confusing, thus requiring a certain amount of practice. The activities described below assume students have never before used Vernier Calipers—they are intended to introduce them to this tool, to provide them with an opportunity to practice using them, and to then apply this new skill in a process of scientific inquiry.

Special Safety Aspects

When the jaw of the calipers is opened, a thin metal guide extends from the bottom of the calipers that could cause injury if students are not careful. Students should be told to take note of this.

Curriculum Objectives

These activities are intended to address Cluster 0 learning outcomes 5a and 5b in both the S1 and S2 curricula, which state that students should “select and use appropriate methods and tools for collecting data or information”, and “estimate and measure accurately using Systéme International (SI) and other standard units”, respectively. It is hoped that through these activities, students will begin to become familiar with Vernier Calipers, both so that they can measure accurately with them, and so that in the future, they will be able to determine if these would be an appropriate measuring tool for any task they might be doing.

Introductory Activity: Learning to use Vernier Calipers

Students will be sitting in small groups, with each group having one set of Vernier Calipers to refer to while the teacher is explaining how to use them. First, the teacher will give a brief overview of Vernier Calipers, explaining that they are a tool used to measure the width, length, and/or height of objects. The teacher should do a quick demonstration, showing how they can be used to measure the thickness of a tabletop, for example.

The teacher will then show the students step by step how to use the calipers. First, the teacher will show how turning the locking screw and sliding the moveable arm along the length of the calipers can adjust the distance between the clamps, and, once they are at their desired position, the locking screw tightened once again. Students will have the opportunity to try this quickly, perhaps by adjusting it to measure the width of their tabletop, for example. The teacher should assist students that are having difficulty at this time, and can answer any questions students have about adjusting the calipers to measure the width of an object.

The teacher should then explain to students how to read their measurements off the calipers, initially by using overhead diagrams. As in the example shown below, the first measurement is taken by looking at where the zero on the lower scale intersects with the upper scale. In this case, the zero line on the lower scale is somewhere just past the 3-millimetre mark on the upper scale. From this, we know that the object is somewhere between 3 and 4 millimetres in length. To find the next decimal place, students are to look at both scales simultaneously, and determine at which point a line on the lower scale seems to match up exactly with a line on the upper scale. Once this spot has been found, the numerical value is to be read off of the lower scale, in this case that number being 7. Since the lower scale for this particular set of calipers measures tenths of a millimetre (as it says 0.1mm on it), we know our measurement must be 3.7mm. The teacher should go through a number of similar examples, have the students try to work out some examples either independently or in small groups, and then have them all measure some standard object and compare their measurements. Throughout, the teacher should be fielding student questions so that by the time this portion of the lesson is over, the students all seem to have a basic understanding of how to use the calipers.

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(Diagram taken from: http://www.phy.uct.ac.za/courses/c1lab/vernier1.html)

Activity 1: Student Practice Using the Calipers

The teacher should then give students an activity sheet (attached here—pg. 3)) that requires them to make measurements of some objects found in the laboratory. Students are to work in small groups, and each student should have the opportunity to take his or her own reading off of the calipers for each measurement taken. The students should compare their readings with their group members to ensure that they are doing it correctly.

Once the students have completed the activity, the teacher should collect group values in a data table on the board, so that their values can be compared in order to ensure that they are on the right track. Any significant problems or misconceptions that are noted here should be addressed before students go on to Activity 2.

Activity 2: Applying the Use of the Calipers

At the front of the room should be approximately 7 blocks of wood of different dimensions. These blocks should be taken from approximately three different kinds of wood. These blocks should be painted, so that students will not be able to tell by sight which blocks have come from the same piece of wood (perhaps each block could be painted a different colour, so that they can be easily distinguished). In their lab groups, students are to have access to at least one pair of Vernier Calipers and an electronic balance (for the purpose of this activity, it will be assumed that students know how to use the balance). Their task for this activity is to use their knowledge of density, as well as the measuring tools they have been given, in order to determine which blocks have come from common pieces of wood. It is assumed that students will have some background knowledge on density, including the formula: density = mass/volume. If this is not the case, some teacher guidance through the beginning of the handout up until where they are required set up their experiment will be necessary. The handout students will receive is attached at back (pp. 4-6).
Using Vernier Calipers

In your lab groups, use Vernier Calipers to take measurements of the following objects found in the laboratory. Each group member should take their own reading off the calipers for each measurement taken, but group members should compare their readings with one another to ensure everyone is using them correctly.

|Object |Measurement (mm) |
|Thickness of lab tabletop | |
|Diameter of chair leg | |
|Thickness of classroom door | |
|Diameter of faucet (measure along the most constant/smooth part) | |

The Mystery Blocks

Introduction

Once upon a time, an evil gnome stole three pieces of wood from a local scientific genius. These pieces of wood were very precious to the scientist, as he had planned to use them as part of some unspecified breakthrough scientific research he was working on. Since he knew it would cause the scientist unending agony, the evil gnome cut the wood into seven pieces, and painted each piece a different colour. The scientist needed to know which painted pieces had come from which original pieces of wood, or his entire life’s research would be destroyed. Though the scientist was considered to be a genius, his lack of access to a good belt sander, or even just some turpentine, left him at a loss as to how to determine which blocks came from which piece of wood.

Hearing of his dilemma, your group has rushed to the rescue. Because of your extensive background in scientific problem solving, you have assured the scientific genius that you will come up with a way to find out which blocks came from which pieces of wood, without even having to remove the paint. Though initially skeptical, he has entrusted these precious blocks into your care. Do not let him down…

Solving the Problem

As a group, you begin to brainstorm. What would you assume about the density of blocks that have come from the same piece of wood? Why?

So density may prove useful to you. But unfortunately, in an attempt to foil your plans, the evil gnome has stolen almost all of your scientific equipment, including your ultra high-tech density-measuring thingamajig. In fact, the only things he has left you with are an electronic balance and a pair of Vernier Calipers. How can you use these to find density?

Some questions to consider: • What do Vernier Calipers measure?

o What are the units for this?

• What does an electronic balance measure?

o What are the units for this?

• What are the units for density?

• How can you use measurements taken with Vernier Calipers and an electronic balance to determine density?

Collecting the Data

Set up some data tables to keep track of the measurements you will take to determine density. You may wish to use the ones shown here, or you may choose to create your own.

|Block |Length (cm) |Width (cm) |Thickness (cm) |Volume (cm3) |
|Red | | | | |
|Green | | | | |
|Blue | | | | |
|Yellow | | | | |
|Orange | | | | |
|Purple | | | | |
|Black | | | | |

|Block |Volume (cm3) |Mass (g) |Density (g/cm3) |
|Red | | | |
|Green | | | |
|Blue | | | |
|Yellow | | | |
|Orange | | | |
|Purple | | | |
|Black | | | |

The Conclusion

1. Based on your data, what blocks do you think came from common pieces of wood? Why?

2. How would you explain to the local scientific genius how you solved the mystery?

3. If it was discovered that the evil gnome had an 8th mystery block he had kept hidden that had come from one of the original three pieces of wood, how should the local scientific genius now determine which piece of wood the block came from?

4. What data might he want of yours? Why?