The design of a watt balance experiment requires skills in several scientific fields and needs to carry out numerous studies about every element of this experiment. That can be illustrated by the experimental study presented in this article. In order to have a single point of application of a weight and an electromagnetic force balancing this weight, a system of double gimbals with flexure pivots was made out of copper-beryllium alloy. It allows the articulation of the suspensions of the mass and coil generating the electromagnetic force round four coplanar axes which intersect in one point (virtual centre of rotation). The static characteristics of these elastic pivots have been studied in terms of stiffness and elasticity limit. In addition, the study of the dynamic behaviour under vacuum of this device has been carried out in terms of resonance frequency, damping due to internal frictions and coupling between the two systems of gimbals.

Air velocity is a quantity often used in specifications of industrial processes or buildings. In these applications, the velocity is generally below 1 m·s^-1, the air temperature can be different from ambient one and the air can flow in any direction whatever. Furthermore, to reach minimum uncertainty measurements, a minimum calibration uncertainty of the used anemometer is needed as well as a calibration as close as possible to measurements conditions. To answer these needs, CETIAT has built a new anemometer calibration test rig. Its evaluation is presented in terms of stability, homogeneity on humidity, temperature and velocity fields as well as calibration uncertainty.

The smallest mass standard sold until now had a nominal value of one milligram. In order to address emerging needs, the joint LNECNAM metrology laboratory decided to produce and calibrate micromass standards with nominal values down to 100 µg. These standards were developed, then tested through multiple comparisons. They have since been qualified and calibrated through a weighing design, repeatedly and over an extended period of time, so as to establish their stability with respect to oxidation and harmlessness of the handling and storage procedures associated with their use. After five successive calibrations no significant drift was found. Finally, in order to enhance this development, the laboratory obtained an extension of its accreditation to perform mass calibration allowing the extension of the lower limit of the scope of accreditation from 1 mg down to 100 µg.

The national accelerometry references in France are provided by the LNE. Such traceability to national standards is essential for industrial organisations using processes in which an understanding of acceleration related parameters is of primary importance in terms of quality and safety. These fields include the armaments, nuclear, aerospace and automotive industries. The calibration of reference accelerometers for industries and other laboratories has been carried out on the LNE site at Trappes since 2006, using an absolute method involving a Michelson laser interferometer in accordance with standard ISO 16063. The bench used, which is described in “Transfert of the french accelerometry reference from CEA/Cesta to LNE” (RFM n° 10, 2007) is however of an old design and an upgrading program has been drawn up and carried out. This article describes the upgrade of this bench and the improvements. The characteristics of the components of the bench are described. These are the laser interferometer, the shaker and the acquisition and analysis system. In order to cover requirements for traceability chains for vibration frequencies below 10 Hz, a specific shaker for low frequencies has been sourced. Metrological approval was based on the consistency achieved between the calibration results for given accelerometers obtained using the new bench and those obtained using the original bench and on the interlaboratory comparisons.

The “watt balance” project aims at linking the kilogram definition to the Planck constant. The weighing of the mass involved requires a determination of the acceleration g with an uncertainty better than 10^-8. This work aims at determining g with an atomic gravimeter and a dedicated gravimetric site.

The continuous expansion method is applied to reference standards of absolute pressure with the aim of improving traceability and reducing uncertainty in the range 1 × 10^-6 Pa to 1 × 10^-3 Pa. It is a realistic goal to reduce the relative uncertainty by a factor of two down to 2.5% (k = 2). This article describes a study of the method carried out at LNE-LCM. It includes a detailed uncertainty budget.

After the development of two new torque standard machines, LNE realized their metrological qualification. This paper describes the determination of the uncertainties of these torque standard machine, including the uncertainty due to the mobility and the sensitivity of the moment arm. It describes also the comparisons carried out with the national metrology institutes of Spain (CEM) and Germany (PTB). The results show that the estimated uncertainties are satisfactory because divided by a factor of at least five compared to the old standard machines.

A simple method based on that described in the international standard NF ISO 5017 is implemented to determine the apparent porosity of samples of limestone. Its effectiveness is demonstrated and the points to be particularly controlled (drying, soaking, wiping) to avoid gross errors are highlighted depending on the type of porosity (thin or wide). This study shows that the standard NF ISO 5017 established for dense shaped refractory products is also well suited for solid rock with homogeneous structure having a true porosity of less than 45 %. This standard properly implemented for rock samples allows one to determine their apparent porosity with a standard uncertainty of about 0.1 %.

This paper contains some errors which are reported to n° 38, vol. 2015-2

A simple method based on that described in the international standard NF ISO 5017 is implemented to determine the apparent porosity of samples of limestone. Its effectiveness is demonstrated and the points to be particularly controlled (drying, soaking, wiping) to avoid gross errors are highlighted depending on the type of porosity (thin or wide). This study shows that the standard NF ISO 5017 established for dense shaped refractory products is also well suited for solid rock with homogeneous structure having a true porosity of less than 45 %. This standard properly implemented for rock samples allows one to determine their apparent porosity with a standard uncertainty of about 0.1 %.

The kilogram is the last unit of the International System of Units (SI) still defined by an artefact, namely the International Prototype of the Kilogram (IPK). Comparisons carried out over 100 years between IPK, its official copies and national prototypes have revealed a mass change (in relative term) of five parts in 108. After a brief history of the unit of mass, this paper underlines the need to redefine the kilogram with reference to a fixed numerical value of a fundamental constant. It explains why the Planck constant h was chosen and gives the last results obtained with watt balance experiments nowadays able to link h to a macroscopic mass to within a few parts in 108. Finally, it proposes a possible route for the national metrology institute for the mise en pratique of the kilogram after its redefinition.