Henri Baumann

Federal Institute of Metrology (METAS) | METAS · Mass and related Quantities

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 d...

After several years of development and continuous improvement, the Kibble balance at the Federal Institute of Metrology (METAS) is now operational. Its stability and reliability allows high precision measurements to be performed under vacuum. Two measurement campaigns were conducted in 2021 with 1 kg stainless steel test masses. The results differ...

The CCM.G-K2.2017 comparison was organised for the purpose of determination of the degree of equivalence of the national standards for free-fall acceleration measurement. The comparison was held in the Changping Campus of National Institute of Metrology China (NIM), from October to November in 2017. This is the first time that such a comparison is...

The watt balance Mark II of the Federal Institute of Metrology METAS is ready to start the measurement of the Planck constant. After an intensive conception phase, the different modules of the experiment have been designed, realized and characterized in close collaboration with external partners. Beside an overview of the experimental setup and som...

A new watt balance experiment is under development at the Federal Institute of Metrology (METAS, Switzerland). Its scope is to link the mass unit to the Plank constant in order to set a new definition of the kilogram, which is no longer based on the international prototype. The experiment is performed in two steps with the same setup and requires t...

Precision absolute gravity measurements are growing in importance, especially in the context of the new definition of the kilogram. For the case of free-fall absolute gravimeters with a Michelson-type interferometer tracking the position of a free falling body, one of the effects that needs to be taken into account is the speed of light perturbatio...

In November 2013 an International Key Comparison, CCM.G-K2, was organized in the Underground Laboratory for Geodynamics in Walferdange. The comparison has assembled 25 participants coming from 19 countries and four different continents. The comparison was divided into two parts: the key comparison that included 10 NMIs or DIs, and the pilot study i...

In order to determine scale factors or more complex calibration functions of relative gravimeters it is usually necessary to calibrate these instruments regularly on points with known gravity values. Especially well suited are points with absolute measurements and with large gravity differences. This implies that gravimetric calibration lines are u...

This paper describes the progress of a joint research project aimed at developing and demonstrating the technologies, based both on the watt balance experiment and the counting of 28Si atoms, necessary to realize the kilogram on the basis of an agreed conventional value of the Planck constant.

In the context of the future definition of the mass unit, a promising approach is to link the kilogram to the Planck constant using, for example a watt balance. The Federal Institute of Metrology METAS is pursuing this route and is currently setting up a second version of the experiment. This METAS watt balance Mark II experiment is now assembled a...

There is a firm will in the metrology community to redefine the kilogram in the International System of units by linking it to a fundamental physical constant. The watt balance is a promising way to link the mass unit to the Planck constant h. At the Federal Institute of Metrology METAS a second watt balance experiment is under development. A decis...

In the early eighties, the development of ballistic absolute gravimeters based on laser interferometer opened the doors to new research areas in various scientific domains such as geodesy, geophysics or metrology. After a brief overview of the most used technique for gravity measurements, the implication of gravity in the context of an improved SI,...

In the context of the future new definition of the mass unit, kg, a promising route to link the mass unit to a fundamental constant, the Planck constant h, is represented by the watt balance experiment. Since a number of years, the Federal Institute of Metrology is active in this field and published a first result with its Mark I experiment in 2011...

It has been recommended that the relative standard uncertainty of the numerical value of the Planck constant required for the redefinition of the kilogram should not exceed 2 × 10⁻⁸. To reach this goal using experiments based on a watt balance, the free-fall acceleration (g) traceable to the SI, at a given point and a given time, needs to be known...

We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared. For the first time, corrections for the laser beam diffraction and the self-attraction of the gravimeters are im...

The kilogram is the last unit of the international system of units (SI) still based on a material artefact, the international prototype of the kilogram (IPK). The comparisons made in the last hundred years have clearly revealed a long-term relative drift between the IPK and the official copies kept under similar conditions at the Bureau Internation...

The European Comparison of Absolute Gravimeters, ECAG 11, was held in the Underground Laboratory for Geodynamics in Walferdange, Luxembourg in November 2011. The ECAG-2011 is registered as EURAMET project 1186 as well as Key Comparison EURAMET.M.G-K1. METAS was the Pilot Laboratory under the leadership of Dr. Henri Baumann. Prof. Dr. Olivier Franci...

The 8th International Comparison of Absolute Gravimeters (ICAG2009) took place at the headquarters of the International Bureau of Weights and Measures (BIPM) from September to October 2009. It was the first ICAG organized as a key comparison in the framework of the CIPM Mutual Recognition Arrangement of the International Committee for Weights and M...

The kilogram is the last unit of the international system (SI) still based on a material artifact, the international prototype of the kilogram (IPK). The comparisons made in the last hundred years have clearly revealed a long term relative drift between the IPK and a set of copies kept under similar conditions. Since the long term stability is one...

We report here the results obtained during a feasibility study that was pursued in order to evaluate the performances of absolute airborne gravimetry. In contrast to relative systems, which use spring-type gravimeters, each measurement acquired by absolute systems is independent from the others and the instrument is not suffering from problems like...

We report here the results obtained during a feasibility study that was pursued in order to evaluate the performances of absolute airborne gravimetry. In contrast to relative systems, which use spring‐type gravimeters, each measurement acquired by absolute systems is independent from the others and the instrument is not suffering from problems like...

The European Metrology Research Programme (EMRP) funds research to address the discrepancy between the values of the Planck and Avogadro constants measured via the watt balance experiments and by the counting of 28Si atoms. The strategy will be to strain the procedures, models, and apparatuses up to their limit by repeating the measurements with ac...

In the frame of the future redefinition of the International System of Units (SI), the unit of mass represents probably the biggest challenge. After the publication of the results from Mark I experiment, the effort is now concentrated on the development of the Mark II system. In this paper, we review the design and present the first tests of the in...

The International Comparison of Absolute Gravimeters 2009 (ICAG2009) was carried out in September 2009 at the International Bureau of Weights and Measures (BIPM). The ICAG2009 and its data processing were performed in accordance with the agreed Technical Protocol which was approved by the Steering Committee. The pilot laboratory (BIPM) evaluated th...

The European Comparison of Absolute Gravimeters, ECAG 11, was held in the Underground Laboratory for Geodynamics in Walferdange, Luxembourg in November 2011. The ECAG�2011 is registered as EURAMET project 1186 as well as Key Comparison EURAMET.M.G�K1. METAS was the Pilot Laboratory under the leadership of Dr. Henri Baumann. Prof. Dr. Olivier Franc...

Accurate gravity measurements were made to support the International Bureau of Weights and Measures (BIPM) watt balance (WB) project in association with the eighth International Comparison of Absolute Gravimeters (ICAG-2009) and the accompanying Relative Gravity Campaign (RGC-2009) at the BIPM in 2009. The goal of WB project is to determine the Pla...

Today's higher precision mechanisms for rectilinear motion are often designed in a monolithic part machined by wire-cut electro discharge machining. The elasticity of the material itself is sufficient to allow a motion, without friction and fatigue problems. A well-known mechanism originally called "simple compound rectilinear spring" is used to ac...

The METAS watt balance project was initiated slightly more than a decade ago. Over this time, the apparatus has been through an uninterrupted series of upgrades that have improved its reliability to a point where continuous series of measurements can be taken fully automatically over periods of several months. A comprehensive analysis of possible s...

We report on the comparison between three absolute gravimeters that took place in April 2010 at Laboratoire National de M\'etrologie et d'Essais. The three instruments (FG5#209 from METAS, Switzerland, IMGC-02 from INRIM, Italy, and CAG from LNE-SYRTE, France) rely on different methods: optical and atomic interferometry. We discuss their difference...

The e-MASS joint research project (JRP) supported by EURAMET gathers several European metrology institutes in the aim to improve existing watt balances and to contribute to a new definition of the mass unit. This paper describes the main technical tasks developed in the framework of the project.

The METAS watt balance project has been in operation for 10 years. After different improvements and modifications, the present setup allows a reproducibility for a two weeks measurement series of 0.05 × 10-6 W/W. The analysis of several measurement campaigns is underway to produce a value of the Planck's constant h in the near future.

An interlaboratory comparison (Euramet Project 1039) of three absolute gravimeters was carried out between the national metrology institutes of Luxembourg, Belgium and Switzerland (University of Luxembourg/ECGS, Royal Observatory of Belgium and Federal Office for Metrology METAS). The comparison was hosted in the Underground Laboratory for Geodynam...

A method is presented that can be used for the evaluation of the value of the Earth gravity field at any defined position inside or outside an instrument used for physical or metrological experiments. After a brief presentation of the gravimeters used and the evaluation of their respective uncertainties, we describe in detail the procedure develope...

After several mechanical improvements, the METAS watt balance has been fully operational during the last 18 months. The reproducibility, alignment issues and the long term stability of the apparatus are discussed.

An interlaboratory comparison (EUROMET Project 852) of four primary standard gas provers was carried out between the Italian and Swiss NMIs (IMGC/INRIM and METAS) from 0.3 m3/h to 25 m3/h using ambient air. The transfer standard was a G25 rotary piston meter. The comparison showed a full compatibility of all four provers above 4 m3/h, whereas at lo...

Velocity distributions of pipe flows acquired in cross sections by Laser Doppler Velocimetry (LDV) are presented. The mostly automated measuring system consists of a so called “window chamber” allowing an extensive optical access with minimum flow disturbance and a three-dimensional iterative beam calculation. Primary and secondary flow structures...

This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and...

For the fabrication of microdevices with line widths approching 1 μm, a patterning methodology has been developed by the modification of an existing plasma etching process, which is suitable for any form and type of diamond.These microdevices have been tested as active sensing elements for both environmental control and metrological applications: v...

The kilogram is the last unit of the international sys-tem (SI) still based on a material artefact, the interna-tional prototype of the kilogram (IPK). The compar-isons made in the last hundred years have clearly re-vealed a long term relative drift between the IPK and a set of copies kept under similar conditions. Since the long term stability is...