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Metrology in Weighing Technology

Working Group 1.15


Working Group 1.15 "Metrology in Weighing Technology" is developing two approaches for the dissemination of the SI base unit kilogram.


  • Setting up of a "Planck-Balance" according to the Kibble principle. After the planned redefinition of the International System of Units (SI), the balance will make it possible to realize the kilogram via the Planck constant h. The continuous weighing range is between 1 mg and 1 kg.


  • Setting up of an infrastructure for the manufacture and dissemination of 1 kg mass standards made out of monocrystalline natural silicon for industry (SI kg). The silicon spheres exhibit form deviations of < 80 nm and roughnesses of < 0.5 nm. The most important characteristics are their long-term stability as well as their robust and highly reproducible cleaning properties.

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Project "Planck-Balance" - A self-calibrating precision balance for industrial applications

A balance according to the Kibble principle is being developed in a collaboration between PTB and the Technische Universität Ilmenau. This balance allows us to calibrate weights in a weighing range from 1 mg to 1 kg. Traceability of the mass determination according to the principle of electromagnetic force compensation (EFC) is not effected by comparing calibrated weights. Instead, the electric measurands are traced to the Planck constant h which, after the redefinition of the SI units, will define the unit kilogram. That is why the name "Planck-Balance" was chosen. In order to make this scale more attractive for industry and to achieve rapid advances in development, we will – as far as possible – use standard components, e.g. commercially available EFC load cells. Thanks to a modular set-up, individual components can easily be replaced and the balance can therefore be adjusted to the user's demands and financial resources. That is why two balances are being developed for this project. The first, called "PB2", is aimed to achieve a relative measurement uncertainty which allows us to calibrate weights of class E2 (according to OIML R111). The balance will cover a continuous weighing range of 1 mg to 100 g. The second balance, designated "PB1", on the other hand, is intended to calibrate weights of class E1 over the weighing range from 1 mg to 1 kg.

The project is funded by the Federal Ministry of Education and Research (BMBF) within the scope of the VIP+ funding program. The project executing agency is the VDI/VDE Innovation + Technik GmbH company.



Dr. Christian Rothleitner


Term: Jan. 2017 – Dec. 2019




Project "Si-kg"

The redefinition of the SI unit kilogram is closely linked to the necessity of an industry-appropriate dissemination of this unit by means of mass standards. Due to its material properties, robustness and easy handling, silicon is very well suited in comparison to other materials that were considered. At PTB, a procedure for the manufacture, handling, storage, transportation, cleaning and metrological assessment of these test objects was developed and studied. This metrological know-how is planned to be tested and developed in cooperation with partners from industry within the scope of the “Si-kg” project that is now funded by the BMWI. The aim is to make these procedures available for a broader use, to strengthen the competence and competitiveness of the participating SMEs and to secure the competitiveness of German industry by making these novel test objects available in the short run.



Katharina Lehrmann


Term: Nov. 2016 – Nov. 2019

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Joint KBTM / IAC 2023 meeting

Next Kibble Balance Technical Meeting (KBTM) will take place on 7-9 November, 2023 at PTB in combination with the Meeting of the International Avogadro Coordination (IAC).

More information will follow soon.

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