ISO Definition of Resolution for Surface Topography Measuring Instruments

Current international standardisation effort in the field of areal surface texture measurement includes the development of a series of documents describing the nominal characteristics of, and calibration methods for, areal surface topography measuring instruments. Technical committee ISO/TC 213/WG 16, which is directly involved in developing such documents, identified, based on the fact that all areal surface topography measuring instruments produce 3D data sets of points [1], a set of metrological characteristics applicable to all these instruments regardless of their design or operation. Metrological characteristics are input quantities, in a measurement model, that can be measured directly [2], generally using calibrated material measures, and make an immediate contribution to the measurement uncertainty associated with the measured coordinates provided by the instrument. The set of metrological characteristics includes: measurement noise; residual flatness; amplification and linearity of the scales; squareness of the axes; and resolution. In two previous papers, methods to determine measurement noise and residual flatness [3] and amplification, linearity and squareness of the axes [4] were presented. A full paper on the determination of resolution is under review at the time of writing [5] and this work is also summarised here.