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TitleA novel hydraulic force standard machine
Publication TypeJournal Article
Year of Publication2002
AuthorsMcIlraith, A.H., and Clarkson M.T.
JournalMeasurement Science and Technology
Pagination1903 - 1909
Date Published2002
ISSN09570233 (ISSN)
KeywordsCalibration, clearance, force, Hydraulics, Hysteresis, Journal bearings, Long-term drift, Thrust bearings
AbstractA hydraulic force standard machine covering the range 40 kN-1.5 MN has been designed, built and tested. Preliminary measurements indicate that this force standard can be self-calibrated to a relative standard uncertainty of 1 × 10 -4 or better and is linear to 0.31 kN. The design of this force standard is suitable for much larger machines generating forces up to 20 MN. The special features of this machine include the use of controlled clearance for the limitation of oil flow, thus enabling the generation of high pressures and large forces, the use of journal bearings external to the high-pressure region to give high stiffness against side thrusts, and a method of calibration that involves determining the slope of the curve force versus pressure. This calibration procedure is essentially a null method that is largely independent of load cell properties such as hysteresis, creep, long-term drift and state of calibration, in contrast to current build-up calibration techniques that are strongly dependent on load cell properties.

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