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Proceedings Paper

Gauge blocks as length standards measured by interferometry or comparison: length definition, traceability chain, and limitations
Author(s): Gerhard Boensch
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Paper Abstract

The length of a gauge block is defined as the distance of a selected point of the measuring face to the plane surface of a platen which consists of the same material and has the same surface texture as the gauge block. With these idealized conditions of the definition, the probing errors due to opposed surfaces and due to the roughness are eliminated. It is assumed implicitly that the surface of the gauge is sufficiently flat so that symmetry in the wringing area is maintained. The assembly of gauge block and platen can be directly measured with an optical wave in an interferometer, and the measurement closely follows to the definition of the length unit>In practice, however, there are always deviations from these idealized conditions and corrections have to be applied. In particular, the wringing influence is important and effects are demonstrated by examples. Results obtained by interferometry are checked by comparison. Under optimum conditions, the comparison method allows nanometer accuracy to be achieved in the determination of length differences if gauges of the same material are compared so that probing errors are eliminated. Both methods have complementary properties and can be applied to systematic investigations. The aim is to obtain a system of gauge block standards consistent within the quoted uncertainties, independent of the method used.

Paper Details

Date Published: 30 September 1998
PDF: 12 pages
Proc. SPIE 3477, Recent Developments in Optical Gauge Block Metrology, (30 September 1998); doi: 10.1117/12.323109
Show Author Affiliations
Gerhard Boensch, Physikalisch-Technische Bundesanstalt (Germany)

Published in SPIE Proceedings Vol. 3477:
Recent Developments in Optical Gauge Block Metrology
Jennifer E. Decker; Nicholas Brown, Editor(s)

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