SLAC Vertical Comparator for the Calibration of Digital Levels
Publication: Journal of Surveying Engineering
Volume 133, Issue 3
Abstract
Digital levels replaced spirit levels in most fields of precise height measurements because of the automation of the height readings. Three manufacturers offer digital levels with a single reading resolution of , and for all of them systematic effects are known. In Europe several facilities for system calibration of digital levels using vertical comparators were established within the last decade. However, there still was no system calibration facility in North America. In order to guarantee the accuracy required for the alignment of experiments at the Stanford Linear Accelerator Center (SLAC) a calibration facility for the system calibration of digital levels was built. In this paper the setup of the SLAC vertical comparator is described in detail and its standard uncertainty is derived. In order to perform traditional rod calibration of conventional line-scaled rods, a CCD camera was integrated into the SLAC comparator. The CCD camera setup is also briefly described. To demonstrate the capabilities of the comparator, results of system and rod calibration are shown.
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Acknowledgments
The writers would like to thank B. Dix and Z. Wolf, both at the SLAC Metrology Department, for helping to build the comparator. Furthermore, they appreciate the assistance of Professor F. K Brunner, Graz University of Technology. The work was supported by the U.S. Department of Energy under Contract No. DOEDE-AC03-76SF00515. The SLAC publication number is UNSPECIFIEDSLAC-PUB-12207.
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Information & Authors
Information
Published In
Journal of Surveying Engineering
Volume 133 • Issue 3 • August 2007
Pages: 144 - 150
Copyright
© 2007 ASCE.
History
Received: Nov 28, 2006
Accepted: Jan 22, 2007
Published online: Aug 1, 2007
Published in print: Aug 2007
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