What is Zeroing Error?

Answer 1

Suppose say you have plastic rule new one. There you will be having zero marking. When you have to measure the length of a rod then you would keep zero marking at one end of the rod and the marking where the other extreme of the rod is taken to be length of the rod. say it is at 4 cm. So 4cm is the length.

And suppose the ruler is an old one whose edge got damaged. Now you don't have zero marking so visible there. So you have keep the end of the rod at say 1 cm marking. Now the error that we commit is known as zero error. Here the error is positive. ie +1 cm.

So as the other end of the rod is at 5cm marking then the correct length is got by applying zero correction. As zero error is +1 cm, then zero correction would be -1 cm

So the correct length 5-1 ie 4 cm.

Same way in case of vernier, if zero of vernier is at left side of zero of main scale, then the zero error is negative.

If zero of vernier is right side of zero of main scale then error is +ve as we have seen in the earlier old ruler case.

Same way in case of screw gauge as the head scale zero is above pitch line then error is negative and as head scale zero is below pitch line then zero error is positive.