Zero Error
A systematic error that occurs when a measuring instrument displays a non-zero reading when the actual quantity being measured is zero.
Governing formula
True Value = Observed Value - Zero Error
SI unit
Various
In depth
Zero error can be positive (reading above zero when closed) or negative (reading below zero). It must be subtracted algebraically from all experimental observations to prevent systematic offset.
Examples in the real world
If a micrometer reads +0.03 mm when fully closed, a measurement of 2.45 mm must be corrected to 2.45 - 0.03 = 2.42 mm.