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