The WIP/RS provides for a highly precise roundness measurement with a rotating probe.  The probe is rotated only through the movement of the highly accurate sensor rotary axis.  The user can move probe from a middle position to an outer position and adjust the desired radius of the cylindrical geometrical element.  This functionality allows one to perform roundness measurements with measurement deviations of approximately 100 nm. Alternatively, the probe can be moved during the rotation with the Cartesian axes of the coordinate measuring machine on a circular path to measure larger geometrical features. The Werth interferometer Probe (WIP) provides for measurements with tight tolerances in deep holes and narrow slits with long measuring probes.  This functionality provides for the ability to measure a cone seat in a fuel injector nozzle at a depth of more than 10 mm exactly to the sub-micrometer.  Another example is the ability to measure the flatness of deep, sensitive bearings in gear housing.  This sensor is also suited for noncontact roughness measurements.  In this case, the precision advantage of the process is of particular significance when compared to the triangulation or focus variation processes.