Sometimes the measuring faces of vernier caliper can become damaged as a result of misuse, and will not read accurately. To address this problem, a zero correction must be made. A zero correction may be either positive or negative.
If the first mark on the vernier scale lies to the right of the main scale zero-mark, the reading is too large and the error is positive. The zero reading is +0.05 cm and should be subtracted from any measurement reading.
If the first mark on the vernier scale lies to the left of the main scale zero-mark, the reading is too small and the error is negative. The zero reading is -0.05cm and should be added to the measurement reading.
