Question

What is meant by zero error of a vernier callipers ?how is it determined ? Draw near diagrams to explain it .How is taken in account to get the correct measurement?

Answer 1

The vernier calliper which shows accurate measurements is said to be having zero error.To see whether the vernier calliper has zero error,the 0 on the vernier scale should match with the 0 on the main scale.

Answer 2

If the zero of vernier scale doesn't coincide with the zero of the main scale, then the instrument i.e., vernier caliper has an error called zero error. Zero error is always algebraically subtracted from the measured length. 

There are two types of zero error:
1. Postive Zero Error 
2. Negative Zero Error

If the zero of the vernier scale lies to the right of the main scale the zero error is positive and if it lies to the left of the main scale then it is negative. 

Positive Zero Error=($N+x\times V.C$)
Here, N: main scale reading on the left of zero of the vernier scale
x= vernier scale division that coincides with any main scale division

The following image shows how positive and negative error is calculated: