Figure 1-39.A multimeter scale with mirror.
The purpose of the mirror on the scale of a meter is to aid in reducing PARALLAX ERROR. Figure
1-40 will help you understand the idea of parallax.
Figure 1-40(A) shows a section of barbed wire fence as you would see it from one side of the fence.
Figure 1-40(B) shows the fence as it would appear if you were to look down the fine of fence posts and
were directly in line with the posts. You see only one post because the other posts, being in line, are
hidden behind the post you can see. Figure 1-40(C) shows the way the fence would appear if you moved
to the right of the line of posts. Now the fence posts appear to the right of the post closest to you. Figure
1-40(D) shows the line of fence posts as you would see them if you moved to the left of the front post.
This apparent change in position of the fence posts is called PARALLAX.
Figure 1-40.Parallax illustration (barbed-wire fence).