A fixed shift in an instrument's output relative to the correct value, most visible as a nonzero reading with zero applied, such as a DMM showing 3 µV with shorted leads or a balance showing 0.2 g with an empty pan. Zero offsets are usually nulled with a zero or tare function before measuring, and any residual offset is corrected or carried in the budget. An offset adds the same error everywhere, unlike a gain error that grows with the reading.
Short the leads and null the offset before you take the low-range readings.
Also heard as
- zero offset
- zero error
Do not mix it up with
- Bias: Bias is the average deviation from a reference at any point; offset is specifically a constant shift, typically seen at zero.
Related terms
Bias
The estimated systematic offset of a measuring system: its average reading minus the reference value.
Systematic error
Error component that pushes every repeat reading the same way, or follows a pattern you can predict and correct.
Correction
The amount added to a raw reading to cancel a known, repeatable error, equal to that error with its sign flipped.
Drift
Gradual change in an instrument's readings over time that comes from the instrument itself, not from what it measures.