Question

How does the zero error arise in the instrument?

Answer 1

If the zero of the one scale (vernier scale or circular scale of screw gauge) does not coincide with the zero of the main scale, this is known as zero scales, zero error arises. There are two types of zero error -
(a) If the zero of the scale remains below the line of graduation of the main scale then it is called positive zero error
(b) If the zero of the scale lies above the line of graduation of the main scale then it is called negative zero error