The concept of a pressure balance based watt balance

Sutton, C M; Fitzgerald, M P; Jack, D G

doi:10.1109/cpem.2010.5544277

Cited by 10 publications

(4 citation statements)

References 3 publications

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“…The linear motion guiding system which uses a piston in a close-fitting vertical cylinder was inspired by the proposal of the MSL watt balance group [8]. The motion guiding system consists of a counter balance module, a flexure-based connector and a linear guide module, as shown in figure 3(a).…”

Section: Guiding Stagementioning

confidence: 99%

Design of the KRISS watt balance

Kim¹,

Woo²,

Lee³

et al. 2014

Metrologia

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We report the design of the KRISS watt balance, which includes a magnet, a guiding stage and a coil position measurement system. The KRISS watt balance incorporates a closed-type cylindrical permanent magnet and a motion guiding stage. For the magnet, a flux shunt is used to reduce flux changes due to temperature variations. A piston gauge is used to achieve linearity in the motion guiding stage. In the weighing mode, the residual force between the weight of the test mass and the Lorentz force generated in a coil is measured by a commercial weighing cell. In the dynamic mode, a linear motor in the motion guiding stage vertically translates the coil and the weighing cell. The in-plane motion of the coil is measured by position sensors, and the out-of-plane motion is measured by single-pass homodyne interferometers.

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Section: Guiding Stagementioning

confidence: 99%

Design of the KRISS watt balance

Kim¹,

Woo²,

Lee³

et al. 2014

Metrologia

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“…The unique apparatus design includes a gas-operated pressure balance to make a precise force measurement: the precision of a pressure balance can approach 1 part in 10 8 , in [175]. A differential pressure balance, as in figure 33 from [176], also adds a mechanical method to control the ac motion. Driving the coil motion without also generating stray magnetic or electrostatic fields is an advantage.…”

Section: Simultaneous Measurement Of Force and Motion: Bipmmentioning

confidence: 99%

History and progress on accurate measurements of the Planck constant

Steiner

2012

Rep. Prog. Phys.

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The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Sin...

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“…A key motivation for this work is improving the weighing performance of a pressure balance based watt balance [1].…”

Section: Introductionmentioning

confidence: 99%