When the jaws of the vernier calipers are fully closed, and the zero marking on the vernier scale does not coincide with the zero marking on the main scale, we have what is called a zero error.
There are two types of zero errors: Positive zero error & Negative zero error.
Positive zero error: The jaws of the vernier calipers are closed and the zero marking on the vernier scale falls to the right of the zero marking on the main scale.
Negative zero error: The jaws of the vernier calipers are closed and the zero marking on the vernier scale falls to the left of the zero marking on the main scale.
How to read the vernier calipers when there is a postive zero error:
For example, if the third vernier mark coincides with a mark on the main scale, it means that the zero error is + 0.03cm
How to read the vernier calipers when there is a negative zero error:
For example, if the eighth vernier mark coincides, the zero error is -0.02.This is because the zero error is two divisions from the tenth division.
Source: Lower Secondary Science Matters
published by Marshall Cavendish Education
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