Negative zero error in vernier calipers

[quietrain]

Homework Statement

Hi, with regards to the negative zero error , do we read the vernier scale from the left or from the right?

In this case, should it be -0.04cm or -0.06cm?

Thank you !

 

[andrevdh]

The vernier scale is normally read from the left. That is when it is slid to the right along the main scale.
Look at A. You will see that first the 0.01 mark will align then the 0.02 one ... if the vernier is slit towards the right,
as it is for normal measurements. But for C is is to the left of the zero on the main scale. That is is has slid a certain
distance to the left of the 0 on the main scale. Now again look at A. The drawing is not completely correct in this case.
The 0 on the right of the vernier should be aligned with the 9 mm mark on the main scale and the next vernier
on the left should be slightly in front of the 8 mm mark, that is slightly to its right - maybe look at a real vernier scale if
possible - the other vernier lines are more or less in their correct positions with respect to the millimeer markings on
the main scale. So if you slide the vernier to the left from this point on the first one that will come into alignment is the
0.09 line then the 0.08 one ... so for negative readings you will get how far the 0 of the vernier is to the left of the 0 on
the main scale by reading it from the right.

 

[quietrain]

The vernier scale is normally read from the left. That is when it is slid to the right along the main scale.
Look at A. You will see that first the 0.01 mark will align then the 0.02 one ... if the vernier is slit towards the right,
as it is for normal measurements. But for C is is to the left of the zero on the main scale. That is is has slid a certain
distance to the left of the 0 on the main scale. Now again look at A. The drawing is not completely correct in this case.
The 0 on the right of the vernier should be aligned with the 9 mm mark on the main scale and the next vernier
on the left should be slightly in front of the 8 mm mark, that is slightly to its right - maybe look at a real vernier scale if
possible - the other vernier lines are more or less in their correct positions with respect to the millimeer markings on
the main scale. So if you slide the vernier to the left from this point on the first one that will come into alignment is the
0.09 line then the 0.08 one ... so for negative readings you will get how far the 0 of the vernier is to the left of the 0 on
the main scale by reading it from the right.

i see , thank you for your explanation.