The METAS 1 kg vacuum mass comparator - adsorption layer measurements on gold-coated copper buoyancy artefacts

Beer, W.; Fasel, W.; Moll, Η.; Richard, Philippe; Schneiter, U; Thalmann, R.; Egger, J

doi:10.1088/0026-1394/39/3/3

Cited by 17 publications

(9 citation statements)

References 6 publications

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“…On moving a mass from air to vacuum, layers of molecules (mostly water) present on the surface are removed and the desorbed mass must be taken into account [ 11 ]. Considerable work has been carried out in this area [ 106 – 108 ] and different techniques [ 109 ] exist to estimate the mass change due to the removal of the sorption layer. In an air-vacuum comparator, the test mass can be compared to a sorption artefact which has the same mass, identical surface properties but a known surface area several times that of the test mass [ 110 ].…”

Section: Design and Operation Of Kibble Balancesmentioning

confidence: 99%

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

2016

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The redefinition of the SI unit of mass in terms of a fixed value of the Planck constant has been made possible by the Kibble balance, previously known as the watt balance. Once the new definition has been adopted, the Kibble balance technique will permit the realisation of the mass unit over a range from milligrams to kilograms. We describe the theory underlying the Kibble balance and practical techniques required to construct such an instrument to relate a macroscopic physical mass to the Planck constant with an uncertainty, which is achievable at present, in the region of 2 parts in 10 8 . A number of Kibble balances have either been built or are under construction and we compare the principal features of these balances.

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Section: Design and Operation Of Kibble Balancesmentioning

confidence: 99%

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

2016

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“…Note that hardness combined with the size of the polishing diamond grains and that of metallographic grains of the material can cause surface quality defects such as an 'orange peel' effect, and the embedding of abrasive particles (phenomena observed with platinum-iridium alloy for instance [24]). -As great a density as possible to minimize volume and an active surface as small as possible thereby reducing the buoyancy effect when the artefact is used in air and sorption phenomena when it is transferred under vacuum [25][26][27][28][29][30][31].…”

Section: Main Properties Of Mass Artefactsmentioning

confidence: 99%

Present and future mass standards for the LNE watt balance and the future dissemination of the mass unit in France

Pinot¹,

Beaudoux²,

Bentouati³

et al. 2016

Metrologia

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The value of the Planck constant h was determined in 2014 by means of the LNE watt balance experiment. The relative standard uncertainty was 31 parts in 10 8 . This first determination was performed in air with a 500 g mass standard made from XSH Alacrite. The main uncertainty components in air associated with the mass involve the calibration, the mass stability, the buoyancy correction and the magnetic interaction correction. The combined relative uncertainty due to the mass is 7.2 parts in 10 8 . The use in 2016 of a mass standard made from platinum iridium alloy significantly reduces the component of uncertainty arising from the mass standard for a Planck constant measurement either in air or under vacuum. The relative uncertainty due to this contribution is estimated to be about 3 parts in 10 8 in air and one part in 10 8 under vacuum. The future system for the dissemination of the mass unit using the LNE watt balance will be based on a primary realization with three 500 g mass standards made from platinum-iridium alloy, pure iridium and Udimet 720 respectively, coupled with a pool of kilograms made from different materials. Pure iridium and Udimet 720 are new materials to make reference mass standards proposed by CNAM and LNE respectively and have never been used by any NMI for manufacturing mass standards until now. Some new results concerning their surface behavior are given.

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“…Thus whenever this stack weight is submerged into the liquid for volume measurement, the volume value would be affected by this gap. A similar design method was described by Beer [13].…”

Section: Recent Research On Surface Artifactsmentioning

confidence: 99%

Surface analytical model and sorption artifact designing method

Ren¹,

Wang²,

Wilson³

et al. 2016

ACTA IMEKO

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Mass standards with alternative shapes are difficult to design due to the number of complex parameters. An analytical model based on surface sorption experiments is presented to study adsorption. This model is based on an optimization algorithm that is conceptualized to help to design the best sorption artefacts. Experimental artefacts, cylinder-weight and stack-weight, were of the same volume but different surface areas. This algorithm in essence determines the optimum surface of the artefact. After machining the artefact, surface sorption measurements were carried out. A sorption experiment was done by transferring the artefact from air to a vacuum. Then the surface sorption model was set up which represented the relationship between sorption coefficient, time t and relative humidity h. Logarithmic models were used to fit the variation of sorption coefficient per relative humidity h with time t.

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The METAS 1 kg vacuum mass comparator - adsorption layer measurements on gold-coated copper buoyancy artefacts

Cited by 17 publications

References 6 publications

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

Present and future mass standards for the LNE watt balance and the future dissemination of the mass unit in France

Surface analytical model and sorption artifact designing method

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