Dorothea Knopf

This paper addresses the ambiguity between the terms representing the result document of a conformity assessment. Among several other terms, such a document is often referred to as a certificate of conformity in the expert communities of standardization and in legislation. This ambiguity has been identified while reviewing various textual sources within a project focusing on the digitization of such a document for legal metrology used in the European Union. This digitization is going to be realized using a unified data structure. This will allow us to semantically describe the complete content of the result document and to make it readable and interpretable for any technical application. In order to bring the data structure in line with the professional language, an appropriate term representing such a result document has to be found from a variety of similar standardized terms. A semantic analysis has been carried out for this purpose. The following publication provides an overview and the results of this analysis, with the aim of making the expert community aware of the existing ambiguity as being a possible cause for the slowing down of digitization processes.

The realisation of the kilogram at PTB is based on the established x-ray crystal density method (XRCD). This method is based on a high-precision characterisation of spheres of isotope-enriched ²⁸ Si. The crystal and material parameters are considered constant and do not need to be re-determined when the realisation of the kilogram is updated. Therefore, the re-determination is primarily based on new measurements of the volume and the mass of the surface layers of the ²⁸ Si spheres. This paper presents new insights in the XRF analysis method used in the XRCD method by PTB and its effects on the volume and mass of ²⁸ Si spheres used as primary mass standards, which provides a basis for participation in the key comparison CCM.M-K8.2024. In the key comparisons CCM.M-K8 from 2019, 2021 and 2024, the definition of the kilogram was realised using the AVO28-S8c and Si28kg01a spheres, as outlined in this document. When applying the new model for the spectral components of the XRF spectrum, realisation results of both spheres show an average mass increase of 13.5 µg.

Main text: This report describes the second CCM key comparison of realizations of the kilogram definition based on the fixed numerical value of the Planck constant, which came into force on 20 May 2019. The objectives were to determine the level of agreement between realizations of the kilogram using Kibble and joule balances and the x-ray crystal density (XRCD) method and to provide input for the calculation of the second "consensus value" of the kilogram. The consensus value serves as the basis for an internationally coordinated dissemination of the kilogram and is updated after each new key comparison. Its use will continue until satisfactory agreement between realization experiments has been achieved. Another objective was the determination of the reproducibility of the realization experiments by comparing the new results with those of the first key comparison of kilogram realizations, CCM.M-K8.2019. The comparison was organized by the BIPM and had nine participants. The BIPM, LNE, METAS, NIST, NRC and UME operated Kibble balances, the NIM used a joule balance and the NMIJ and the PTB participated using 28Si spheres, the masses of which were determined with the XRCD method. These realization methods were used to calibrate 1 kg mass standards under vacuum or in air. The standards were sent to the BIPM where they were compared with each other and with BIPM Pt-Ir working standards. The latter were calibrated traceable to the International Prototype of the Kilogram (IPK), the mass of which served as the definition of the kilogram until 20 May 2019. The results of the weighings at the BIPM together with the measurement results communicated by the participants allowed comparison of the values attributed to 1 kg mass standards using the realization experiments of the participants. The level of agreement between mass determinations with the realization experiments and the BIPM as-maintained mass unit, traceable to the Planck constant through the mass of the International Prototype of the Kilogram, could also be deduced. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Article Frontmatter was published on December 1, 2021 in the journal tm - Technisches Messen (volume 88, issue 12).

A table-top version of a Kibble balance called Planck-Balance 1 (PB1) has been developed in a collaboration between the Physikalisch-Technische Bundesanstalt and the Technische Universität Ilmenau. It is aimed for calibrating E1 mass standards for a mass range from 1 mg to 1 kg. This paper gives a brief overview of the concept of the PB1, its measurement setup, and some initial measurements of the force mode and the velocity mode.

ZusammenfassungAm 20. Mai 2019 hat die Generalkonferenz für Maße und Gewichte die Definition zur Darstellung der Einheiten grundlegend erneut. Die Einheit Kilogramm des Internationalen Einheitensystems (SI) stand besonders im Fokus, da vermutet wurde, dass sich die Masse des Internationalen Kilogramm Prototyps (IPK) über die Zeit ändert. Wie auch andere SI-Einheiten wird das Kilogramm nun nicht mehr durch einen weltweit einzigen physikalischen Körper dargestellt, sondern über physikalische Konstante. Auswirkungen auf industrielle oder gesellschaftliche Anwendungen hat die neue Definition nicht, auch wenn sich die Genauigkeit der nationalen Massenormale etwas verschlechtert hat. Die Chancen liegen dagegen in der Vielfalt, mit der das Kilogramm künftig dargestellt werden kann. Grundlage für die neue Realisierung bilden derzeit zwei Experimente, die „Kibble-Waage“ (Kibble-Balance: KB) und die „X-Ray Crystal Density Method“ (XRCD-Methode). Letztere basiert auf Kugeln aus monokristallinem isotopenangereichertem Silizium. Systematische Abweichungen zwischen den beiden Experimenten zeigen, dass eine dreistufige Übergangsphase notwendig ist, um die grundlegende Stabilität für die Weitergabe der Größe Masse zu gewährleisten. Der IPK und ein sogenannter Consensus Value (CV) spielen dabei eine besondere Rolle. Die gute Handhabbarkeit und Stabilität von Silizium haben dazu geführt, dass die in der XRCD-Methode verwendeten Siliziumkugeln in ihrer natürlichen Isotopenzusammensetzung auch als sehr stabile Massenormale eingesetzt werden.

Zusammenfassung: Seit dem 20. Mai 2019 gilt das neue Internationale Einheitensystem SI. Dies stellt eine Zäsur in der Geschichte der Einheiten dar, denn von nun an sind alle 7 Basiseinheiten durch Fundamentalkonstanten definiert. Gerade für die Masse und die daraus abgeleiteten Größen hat das weitreichende Folgen. Das Urkilogramm ist jetzt nur noch ein normales 1 kg-Wägestück. Der Gewinn aber ist enorm. Das Kilogramm lässt sich zukünftig für jeden Massewert darstellen und muss nicht mehr auf das Urkilogramm rückgeführt werden. Da die Kraft bislang über die Masse rückgeführt wurde, öffnen sich aber auch deren Definition neue Wege. In diesem Artikel soll beschrieben werden, wie die prinzipiellen Realisierungen des Kilogramms über die Kibble-Waage und die Röntgenkristalldichtemessungen (XRCD-Methode, oder auf Englisch X-ray-crystal-density method) funktionieren und welche Ideen für die Kraft-Messung bereits umgesetzt wurden.

In a forecast of the revised international system of units, that will come into force on 20th May 2019, the Physikalisch-Technische Bundesanstalt is developing and establishing a strategic concept, that allows the kilogram to be realized and distributed on the basis of new artefacts and methods. Possible paths of the quantum-based kilogram from its definition based on the Planck constant to the macroscopic world are being elucidated, i.e. the use of silicon spheres of different qualities as well as the use of Kibble-Balances and new developments of table-top weighing instruments. Beside metrological aims the availability of realizations and easy handling procedures are of crucial importance within a future dissemination chain. Advantages and disadvantages of different approaches are being examined and current developments, basically on the silicon route, and their expected measurement uncertainty are outlined. Scientific and strategic developments in the use of silicon spheres in the future mass dissemination chain are accompanied by more than 20 national metrological institutes and designated institutes by testing the existing methods and doing their own investigations.

A balance is proposed, which allows the calibration of weights in a continuous range from 1 mg to 1 kg using a fixed value of the Planck constant, h . This so-called Planck-Balance (PB) uses the physical approach of Kibble balances that allow the Planck constant to be derived from the mass. Using the PB no calibrated mass standards are required during weighing processes any longer, because all measurements are traceable via the electrical quantities to the Planck constant, and to the meter and the second. This allows a new approach of balance types after the expected redefinition of the SI-units by the end of 2018. In contrast to many scientific oriented developments, the PB is focused on robust and daily use. Therefore, two balances will be developed, PB2 and PB1, which will allow relative measurement uncertainties comparable to the accuracies of class E2 and E1 weights, respectively, as specified in OIML R 111-1. The balances will be developed in a cooperation of the Physikalisch-Technische Bundesanstalt (PTB) and the Technische Universität Ilmenau in a project funded by the German Federal Ministry of Education and Research.