The closeness of a measured quantity to the actual quantity that was measured, the measurand. Sometimes thought of as a tolerance range on a measurement’s value. Often used colloquially as a synonym f [..]

The state or orientation of an object or feature with respect to a set of datums or the act of putting an object or feature into a desired state or orientation. Example alignments include: setting sev [..]

Or the As-built condition. Refers to the actual dimensions of a part or assembly as it was manufactured. Also sometimes called “As-found”.

A precision fixture that can be used as a standard of length.   Ball-bars are often built with precision nests to accept Sphere Mounted Reflectors or precision ball bearings to aid in checking or cali [..]

This term refers to an old method for setting sights on a firearm, in which the bolt or part of the action was removed and a target point was viewed alternately through the bore and through the sights [..]

This acronym stands for Coordinate Measuring Machine. These machines measure parts through the acquisition of points. Many types of CMMs exist, traditional 3 axis contact probing machines, articulated [..]

In metrology,  a datum is simply an idealized reference feature from which another features’ orientation, position, or other characteristic is defined.   Datums can be many types of features, planes, [..]

A datum feature is the measured or contacted feature which establishes a datum.  It is an actual point, line or surface on the part being measured.

The process of characterizing an object’s size and shape through measurements of points, lengths, and volumes.  Usually such an inspection results in a report comparing the measured object to another [..]