AVS 53rd International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuA

Paper VT-TuA6
A Comparison of the High Vacuum Standards of the National Physical Laboratory of India and the National Institute of Standards and Technology, USA at 0.05 Pa using the Spinning Rotor Gauge

Tuesday, November 14, 2006, 3:40 pm, Room 2000

Session: Extreme High Vacuum and Vacuum Metrology
Presenter: P.J. Abbott, National Institute of Standards and Technology
Authors: P. Mohan, National Physical Laboratory, India
P.J. Abbott, National Institute of Standards and Technology
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High vacuum (10@super-1@ to 10@super-4@ Pa) standards are maintained by many of the world's National Metrology Institutes (NMI). For purposes of trade equity as well as scientific integrity, it is important that NMI's compare their standards and determine a degree of equivalence within a well documented uncertainty. Comparing high vacuum standards presents a special challenge, as the transfer standards available for use in this range measure pressure indirectly and tend to have much larger uncertainties than the transfer standards used for comparing medium and low vacuum standards.@footnote 1@ The spinning rotor gauge (SRG) has excellent stability and its calibration has been found to be independent of pressure in the high vacuum regime. For these reasons, two SRG's were used to compare the high vacuum standards of the National Physical Laboratory of India (NPLI) and the National Institute of Standards and Technology, USA (NIST) at a pressure of 0.05 Pa. NPLI served as the pilot lab for the comparison. To minimize the possible effects of rough handling during shipping, the rotors were carefully packed and hand-carried between India and the United States and back to India. At each laboratory, multiple measurements of the accommodation coefficients of two rotors were made using the respective high vacuum standards of NPLI and NIST. A discussion of these standards along with the results of the comparison will be presented. @FootnoteText@ @footnote 1@Final report on key comparison CCM.P-K5 of differential pressure standards from 1 Pa to 1000 Pa A P Miiller, G Cignolo, M P Fitzgerald and M P Perkin Metrologia 39 No 1A (Technical Supplement 2002) 07002 .