When making some kind of scientific measurement. It is necessary to first check your instrument for ‘zero error’. The zero error is the reading displayed when you know the true reading should be exactly zero.

          For example, using a set of Vernier calipers, the zero is the reading that shows when the calipers are fully closed.

         As long as check for zero error, you can then use it to correct your readings.

Positive zero error:

          Zero error will be positive if the zero lines of the Vernier scale are on the right side of the zero of the main scale.

To get the correct value zero error must be recorded and subtracted from each reading.

Negative zero error:

          Zero error will be negative if the zero lines of the Vernier scale are on the left side of the zero of the main scale.

To get the correct value zero error must be recorded and added to each reading.