Dimensional metrology: angle calibration

Development of an angle reference turntable with an uncertainty of 0.03''

• The new national reference for angle calibration - developed for the French Bureau National de Métrologie (BNM) in the BNM-LNE dimensional metrology laboratory - is a continuous-positioning turntable with rotational uncertainty in the region of a ± 0.03'' angle.

• The turntable has been developed to an entirely new design based on the dissociated structure principle, ie. the installation structure and metrological structure are completely separated. The two internal encoders are mounted in such a way that the turntable position data is independent of any inaccuracies intrinsic to the encoders used.

• The turntable offers continuous positioning through several rotations, unlike indexing tables which have only a finite number of positions through one rotation.

• It is used with a Möller Wedel Elcomat HR autocollimator with 0.005'' resolution.

• Calibration uncertainties for angle, polygon and indexing table gauges are between 0.06'' and 0.1'', depending on the calibration method used and the quality of the standard measured.

• With this new turntable LNE can also calibrate autocollimators to uncertainties that are limited only by the instrument undergoing calibration.

Contact : Georges Vailleau