Repeatability

Repeatability is a measure of how consistently an instrument produces the same result when the same quantity is measured multiple times under conditions that are kept as constant as possible. These "repeatability conditions" include the same measurement procedure, the same operator, the same instrument used under the same conditions, the same location, and repetition over a short period of time.

Repeatability is quantified using the standard deviation of a series of repeated measurements, sometimes expressed as a repeatability limit (the value below which the absolute difference between two successive measurements should fall with 95% probability). It represents the best-case precision of a measurement system because all variable factors are held constant.

In calibration, repeatability is a critical performance characteristic. It is evaluated during calibration by taking multiple readings at each test point. Poor repeatability may indicate mechanical wear, electrical noise, environmental interference, or internal friction. The repeatability standard deviation is often the dominant Type A uncertainty component in the uncertainty budget. Instruments with poor repeatability may need repair or replacement regardless of their accuracy, because inconsistent readings undermine confidence in every measurement they produce.