Vernier Calipers

Vernier Calipers

General Information:

The vernier caliper permits measuring with greater accuracy and precision than a ruler. The use of the vernier caliper is illustrated below in Figure 1. The object to be measured is placed in the jaws of the caliper.

Figure 1: Use of Vernier Caliper

How to Read:

The value of the dimension being measure is indicated by the proportion of the zero mark on the sliding scale (also called vernier scale) below the main scale. The units digit and first decimal place are read from the main scale. The value of the second decimal place is determined from the vernier scale. The value of the second decimal is given by whichever line on the vernier scale best lines up with a line on the main scale.

Example 1:

For the square in Figure 1, the main scale reading is between the 0.8 and 0.9 lines. This is somewhat hard to see because some of the lines between 0 and 1 are obscured by the sliding jaw of the caliper. In such a case, it is normally easiest to count BACKWARD from the nearest labeled line that can be clearly seen.

Now look at the lines on the sliding (vernier) scale. I think that the eighth line best lines up with the line above it on the main scale. The value of the first line on the sliding (vernier) scale is zero, the second line is 0.01, the third is 0.02, and so on. This means that the second decimal place is 0.01. This means that the second decimal place is 0.08. Thus, the proper value for the side of this square is 0.88 cm.

Example 2:

The use of the vernier caliper is illustrated again below in Figure 2. However, this time the length of a metal slug is being measured. This is what you will be doing in the Comparison of Properties lab. Notice that to measure the length the slug is place lengthwise in the jaws of the caliper.

Figure 2: Measuring the Length of a Metal Slug

For the slug above, the main scale reading is between the 3.5 and 3.6 lines. Now, look at the lines on the sliding (vernier) scale. I think that the second line best lines up with the line above on the main scale. Remember, the value of the first line on the sliding (vernier) scale is zero, the second line is 0.01, the third is 0.02, and so on. . Thus, the proper value for the length of this slug is 3.51 cm.

Example 3:

The use of the vernier caliper is illustrated one last time below in Figure 3. However, this time the diameter of a metal slug is being measured. This is what you will be doing in the Comparison of Properties lab.

Figure 3: Measuring the Diameter of a Metal Slug

For the slug above, the main scale reading is between the 0.4 and 0.5 lines. Now, look at the lines on the sliding (vernier) scale. I think that the sixth line best lines up with the line above on the main scale. Remember, the value of the first line on the sliding (vernier) scale is zero, the second line is 0.01, the third is 0.02, and so on. Thus, the proper value for the length of this slug is 0.45 cm.

Practice Problem:

Find an equation to calculate the volume of this (and any other) metal slug (use the volume of a cylinder). Then use the proper values of the length and diameter found above to calculate the volume.