Uncertainty of measurement in the determination of Roughness parameters using contact stylus instruments

A model is presented to describe the sources of measuring uncertainty starting with the process of contacting through to the calculation of roughness parameters. It can be seen, that the uncertainty of the measurement result changes dependent on the state of knowledge about the sources of measuring uncertainty. As an example, it is demonstrated that by employing a surface parameter as a statistical variable the uncertainty can be expressed more precisely than in usual practice.