Question

Why do we use zero correction?

Answer 1

The use of zero correction

1. Zero correction is used in an instrument for removing the zero error.
2. It is necessary to remove zero error for measuring instruments accurately and it also helps in checking whether the instrument is working properly or not.
3. These errors occur when the primary marking on the instruments does not coincide with the zero marking of the instrument like screw gauge, Vernier caliper, etc.

Positive zero error happens when the zero of the main scale coincides with a value above zero(here 1,2,3,…) on the vernier scale. In the figure we can see that the zero error has a positive value in this case.

For eg, in case of a positive zero error $+0.03mm$, the zero correction is $-0.03mm$

Negative zero error happens when the zero of the main scale coincides with a value below zero(here 49,48,47,…) on the vernier scale. In the figure we can see that the zero error has a negative value in this case.

For eg, in case of a negative zero error $-0.02mm$, the zero correction is $+0.02mm$

Hence, zero correction is used to remove zero error.