Some national laboratories of metrology carry out the continuous expansion method to ensure measurements traceability for low absolute pressure. This method implies to generate a reference molar gas flow rate ranging from 4 × 10^-12 mol·s^-1 to 4 × 10^-7 mol·s^-1. To improve calibrations uncertainties for pressures below 10^-3 Pa, Laboratoire national de métrologie et d’essais (LNE) had to initially design a primary reference for gas flow measurement in the aforementioned range, with an expected expanded uncertainty better than 1%. With the gas flowmeter, it will also be possible to calibrate reference leaks, which is an usual activity of the pressure department of the LNE, for the leaks with reference to vacuum between 4 × 10^-12 mol·s^-1 and 4 × 10^-7mol·s^-1 (from 1×10^-8 Pa·m3·s^-1 to 1×10^-3 Pa·m³·s^-1) and leaks of the cooling agent R-134a with reference to atmospheric pressure between 3×10^-9 mol·s^-1 and 2 × 10^-8 mol·s^-1 (from 10 g per year to 60 g·per year). The calibration results of a capillary leak are compared with the pressure rise calibration method, usually performed for this kind of instrument. An uncertainty budget on the gas flow measurement is established for this calibration and applied to the continuous expansion method.

Within the research project “surface activity analysis”, stretching over different metrological and technological topics, mass and nanotechnology for instance, improvements and adaptation have been carried out on different surface analysis devices in laboratories. The goal of this paper is to propose a review of the different developed devices, describing their main improvements for the past four years and to present the experimental results they produced.

The kilogram is still defined in terms of an artefact, namely, the same prototype sanctioned by the 1st CGPM in 1889. It has three main limitations: available in one place, not really invariant in terms of physical mass and not universal as based on an artefact. The definition of the mass unit could be revised as early as 2011 by basing it on exactly fixed value of a fundamental constant of nature. Thus, the possibility of redefining the kilogram in function of a true natural invariant has been discussed for about 30 years. In this context, the French metrology decided in 2002 to undertake the realisation of a watt balance experiment aiming at linking the kilogram to the Planck constant. The adoption of a new definition of the kilogram based on an atomic or a fundamental physical constant has to take its dissemination into account by avoiding great change for the accredited institutes and most of users. Of course, this will have consequences for the transfer mass standards used by the National Institutes of Metrology.

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.