Flatness departures of surface plates are generally obtained from straightness measurements of lines on the surface. A computer program has been developed for on-line measurement and evaluation, based on the simultaneous coupling of measurements in all grid points. Statistical methods are used to determine the accuracy of the measurements. The program runs on standard personal computers and supports different types of measuring instruments like electronic levels, autocollimators, laser interferometers or straight edge based instruments. Apart from the given height map, some meaningful characteristic parameters: sphericity, torsion and waviness are obtained. They have been proven very valuable to record long term effects of surface plates. Reliable measurements with an accuracy of 0.1 μm/m demonstrate the capabilities of the method.
- surface plate