Mass and density


The laboratory is mostly active in the determination of the mass and the density which is an important influence factor of mass metrology.


The laboratory has a traceability to the international prototype in Paris through its national copy which number is 38.

The laboratory has established several sets of mass by defining multiple and submultiples of the national prototype. These mass sets are used for the dissemination of the mass unit.

The laboratory is equipped with several mass comparators according to measuring range and is able to determine the mass in air, under controlled atmosphere or under vacuum.

Influence values

The laboratory is also able to determine the influence values of the mass metrology.

Surface analysis

The laboratory is equipped with a measurement system for the determination of surface contaminants and their influence on the mass of an object. The system includes several vacuum chamber connected together with each chamber dedicated to a specific measurement. The sample can be weighted, the surface can be analysed by x-ray photoelectron spectroscopy or Auger electron spectroscopy. It is also possible to clean the surface by exposure to a plasma.


The laboratory is working according to the norm ISO 17025 and our certificates are recognised worldwide.


We are working according to the recommendation OIML R-111. We are able to calibrate mass of the precision class E1 and E2 from 1 mg to 50 kg and mass of precision F1 and lower from 1 mg to 10'000 kg.

Volume and density
In the case of a first calibration for high precision mass we determine the density of the artefact. This measurement is not needed for recalibration as it is a property of the material and is not affected by ageing.

The volume or density is determined by double weighting in air and water. We are able to determine the magnetization as well as the magnetic susceptibility of artefacts. We are also able to determine the position of the center of mass of a weight.

Research and development

In order to maintain an uncertainty and a calibration span in correlation with the need of our customers, we continuously improve our measurement systems and our procedures. This research and development effort is performed internally but also in the framework of projects with other national metrology institutes or with private partners.

Our main research directions are focused on the following topics :

Determination of the density by double weighting in air of different density. This techniques alleviates the potential contamination from water.

Study of surface contaminants in order to optimize the material used for the artefacts, the cleaning process and the storage conditions.

Study of surface contaminations after air exposure of mass previously stored under vacuum. This should improve the vacuum to air transfer of the unit in the case of the new definition of the kilogram.

Last modification 26.02.2024

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Federal Institute of Metrology
Laboratory Mass, Force and Pressure
Lindenweg 50
CH-3003 Bern-Wabern
T +41 58 387 01 11

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