What is meant by zero error of a vernier calliper? How it is determined ?

Dear Student, 
Please find below the solution to the asked query: 

• Zero error: When zero of main scale doesn't coincides with zero of vernier scale, then the error is said to zero error.
• When zero of main scale lies towards right side zero of vernier scale without placing any object, then the error is said to be positive zero error and correction is said be negative.
• When zero of main scale lies towards left side zero of vernier scale without placing any object, then the error is said to be negative zero error and correction is said be positive.

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