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Fertigungskette von Si-Kugeln und interferometrische Bestimmung des Kugelvolumens

SI-traceable determination of the spring constant of a soft cantilever with 0.3 % uncertainty

01.12.2015

The PTB’s nanonewton force facility has been significantly improved and was used to measure the stiffness of a soft cantilever. The facility is based on a disc pendulum with electrostatic reduction of its deflection and stiffness. We have demonstrated that the facility is able to measure horizontal forces in the range below 1 µN with a resolution below 5 pN and an uncertainty below 1.5 % for a measured force of 1 nN at a measuring duration of about 20 s. Further we have demonstrated the possibilities to use this facility as a calibration device which can accurately determine spring constants of soft cantilevers (K ≲ 0.1 N/m) traceable to the SI units. The method and the results of measuring the spring constant of a soft cantilever (K = 0.124 N/m) in air, in a medium vacuum, in a high vacuum and in nitrogen atmosphere are presented. We have shown that a relative standard uncertainty of the spring constant calibration of better than 0.3 % (measurement in a medium vacuum) and a repeatability of better than 0.04 % are achieved.


Figure 1. Measured stiffness of the cantilever in a medium vacuum

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Physikalisch-Technische Bundesanstalt
Bundesallee 100
38116 Braunschweig