A non-negative measure of the dispersion of values that can be attributed to the quantity being measured, based on the available information.
Also called: uncertainty of measurement; capsule thickness measurement uncertainty; measurement result uncertainty.
Measurement uncertainty vs dimensional tolerance
No. Tolerance describes the specified dimensional allowance; measurement uncertainty describes the range or dispersion of values attributable to the defined measurand using the available information. An error is a difference from a reference or true value under its definition, rather than another word for uncertainty.
Model the actual measurement and its significant inputs, including relevant systematic effects. Define the shell feature and conditions first. Uncertainty in one local thickness result is not automatically a measure of variation across the entire batch.
Does a stable high-resolution reading mean low uncertainty?
Not by itself. Resolution concerns display or scale discrimination; repeatability concerns consistency under specified conditions. Neither alone includes all material, contact, calibration or alignment effects. Changing how the part is contacted can also change the measurement.
Report the value, unit and whether uncertainty is standard or expanded; for an expanded value retain the coverage factor and the basis used. Do not automatically describe every k = 2 result as exactly 95% coverage. A useful evaluation identifies the significant components and assumptions rather than appending the instrument’s smallest display increment as the uncertainty.