Resolution

Resolution is the smallest distinguishable difference between two measurement values that an instrument can indicate. For a digital instrument, resolution is typically the smallest digit displayed (e.g., a digital caliper reading to 0.01 mm has a resolution of 0.01 mm). For an analog instrument, resolution is related to the smallest graduation on the scale and the observer's ability to interpolate between marks.

Resolution should not be confused with accuracy or precision. An instrument may have very fine resolution but poor accuracy if it is not properly calibrated. Conversely, a coarse-resolution instrument might be highly accurate at the values it can display. Resolution sets a lower bound on the measurement uncertainty — you cannot reliably measure changes smaller than the instrument's resolution.

In calibration management, resolution is a key specification when selecting instruments for a measurement task. The instrument's resolution must be significantly finer than the tolerance being measured to ensure meaningful results. A common guideline is that the instrument resolution should be at least one-tenth of the tolerance. Additionally, resolution contributes to the uncertainty budget as a Type B uncertainty component, typically modeled as a rectangular distribution with a half-width equal to half the resolution.