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Moldover M.R.,U.S. National Institute of Standards and Technology | Gavioso R.M.,INRIM - Istituto Nazionale di Ricerca Metrologica | Mehl J.B.,PO Box 307 | Pitre L.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | And 2 more authors.
Metrologia | Year: 2014

We review the principles, techniques and results from primary acoustic gas thermometry (AGT). Since the establishment of ITS-90, the International Temperature Scale of 1990, spherical and quasi-spherical cavity resonators have been used to realize primary AGT in the temperature range 7 K to 552 K. Throughout the sub-range 90 K < T < 384 K, at least two laboratories measured (T - T90). (Here T is the thermodynamic temperature and T90 is the temperature on ITS-90.) With a minor exception, the resulting values of (T - T90) are mutually consistent within 3 × 10-6 T. These consistent measurements were obtained using helium and argon as thermometric gases inside cavities that had radii ranging from 40 mm to 90 mm and that had walls made of copper or aluminium or stainless steel. The AGT values of (T - T90) fall on a smooth curve that is outside ±u(T90), the estimated uncertainty of T90. Thus, the AGT results imply that ITS-90 has errors that could be reduced in a future temperature scale. Recently developed techniques imply that low-uncertainty AGT can be realized at temperatures up to 1350 K or higher and also at temperatures in the liquid-helium range. © 2014 BIPM & IOP Publishing Ltd.


Pavese F.,INRIM - Istituto Nazionale di Ricerca Metrologica | Steur P.P.M.,INRIM - Istituto Nazionale di Ricerca Metrologica | Hermier Y.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Hill K.D.,National Research Council Canada | And 11 more authors.
AIP Conference Proceedings | Year: 2013

The paper summarizes the results of an International Project started in 2003 aimed at formulating a correction for the variability of isotopic composition found in 'natural' neon, and presently not taken into account by the ITS-90 definition, whose consequent ambiguity leads to a combined uncertainty uc = 160 μK, whereas uc = 30-50 μK for the rest of the budget. After a very short summary of the Project results (a detailed Final Report will be published later) recommendations for the correction function are presented, in agreement with both the experimental data and the theoretical calculations. © 2013 AIP Publishing LLC.


Mokdad S.,LNE CETIAT | Mokdad S.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Georgin E.,LNE CETIAT | Hermier Y.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | And 2 more authors.
Review of Scientific Instruments | Year: 2012

Progress in the knowledge of the water saturation curve is required to improve the accuracy of the calibrations in humidity. In order to achieve this objective, the LNE-CETIAT and the LNE-CNAM have jointly built a facility dedicated to the measurement of the saturation vapor pressure and temperature of pure water. The principle is based on a static measurement of the pressure and the temperature of pure water in a closed, temperature-controlled thermostat, conceived like a quasi-adiabatic calorimeter. A copper cell containing pure water is placed inside a temperature-controlled copper shield, which is mounted in a vacuum-tight stainless steel vessel immersed in a thermostated bath. The temperature of the cell is measured with capsule-type standard platinum resistance thermometers, calibrated with uncertainties below the millikelvin. The vapor pressure is measured by calibrated pressure sensors connected to the cell through a pressure tube whose temperature is monitored at several points. The pressure gauges are installed in a thermostatic apparatus ensuring high stability of the pressure measurement and avoiding any condensation in the tubes. Thanks to the employment of several technical solutions, the thermal contribution to the overall uncertainty budget is reduced, and the remaining major part is mainly due to pressure measurements. This paper presents a full description of this facility and the preliminary results obtained for its characterization. © 2012 American Institute of Physics.


Madec T.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Amarouche S.,French National Laboratory of Metrology and Testing
3rd International Metrology Conference 2010, CAFMET 2010 | Year: 2010

In the context of improving the process of calibration of the Piston-Operated Volumetric Apparatus (POVA) called micropipettes, the 5 accredited laboratories marketing these instruments in France formed a working group, with the approval of the Cofrac (French Accreditation Body). To evaluate the performance of the standardized method used [1] [2] and identify certain factors of influence, the group decided to organize an interlaboratory comparison. This comparison included 5 volumes covering a broad range, and so constituted five comparisons, carried out between September 2009 and January 2010. In all, no fewer than 100 calibrations, each including 10 determinations, were performed. The proposed article sums up the results of this comparison, the only one of its kind, and presents the lines of progress found: improved evaluation of the calibration uncertainty, better training of the operators, warning against the use of universal cones rather than the manufacturers' cones, and precautions to be taken when transporting the instruments. This first stage of study opens up prospects of optimizing the standardized method in its context of application.


Pitre L.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Sparasci F.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Truong D.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Guillou A.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | And 2 more authors.
International Journal of Thermophysics | Year: 2011

There is currently great interest in the international metrological community for new accurate determinations of the Boltzmann constant k B, with the prospect of a new definition of the unit of thermodynamic temperature, the kelvin. In fact, k B relates the unit of energy (the joule) to the unit of the thermodynamic temperature (the kelvin). One of the most accurateways to access the value of the Boltzmann constant is from measurements of the velocity of the sound in a noble gas. In the method described here, the experimental determination has been performed in a closed quasi-spherical cavity. To improve the accuracy, all the parameters in the experiment (purity of the gas, static pressure, temperature, exact shape of the cavity monitored by EM microwaves, etc.) have to be carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic and microwave signals.We report on two sets of isothermal acoustic measurements yielding the value k B = 1.380 647 74(171) × 10 -23 J ̇ K -1 with a relative standard uncertainty of 1.24 parts in 10 6. This value lies 1.9 parts in 10 6 below the 2006 CODATA value (Mohr et al., Rev. Mod. Phys. 80, 633 (2008)), but, according to the uncertainties, remains consistent with it. © The Author(s) 2011.


Sparasci F.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Didialaoui I.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Verge A.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Hermier Y.,Laboratoire Communications Of Metrologie Lne Cnam Lcm
AIP Conference Proceedings | Year: 2013

The LNE-Cnam has recently developed a new quasi-adiabatic calorimeter for the realization of the triple point of mercury (234.3156 K) at the highest degree of accuracy. The device can accommodate long-stem Standard Platinum Resistance Thermometers (SPRTs) and capsule-type SPRTs (CSPRTs). It can be used to realize simultaneous calibrations of SPRTs and CSPRTs, and to study the temperature evolution of the triple point when the fraction of melted substance changes. The device is composed of a triple point cell installed in a vacuum-tight adiabatic calorimeter, where CSPRTs are mounted, with a central reentrant well for housing long-stem SPRTs. The well is surrounded by a shield cell filled with mercury and its upper part is at the ambient temperature. Five mercury triple point cells have been recently filled and characterized at the LNE-Cnam. Measurements have been carried out with both long-stem and capsule-type SPRTs. Triple point uncertainties of 0.2 mK for the calibration of CSPRTs, and of 0.3 mK for the calibration of long-stem SPRTs have been obtained. © 2013 AIP Publishing LLC.


Pitre L.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Sparasci F.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Truong D.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | Guillou A.,Laboratoire Communications Of Metrologie Lne Cnam Lcm | And 2 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2011

The paper reports a new experiment to determine the value of the Boltzmann constant, kB =1.3806477(17) × 10-23 JK -1, with a relative standard uncertainty of 1.2 parts in 10 6. kB was deduced from measurements of the velocity of sound in argon, inside a closed quasispherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of kB is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k new B /kBCODATA -1)=-1.96 × 10 -6, where the relative uncertainties are μr(k new B )=1.2 × 10 -6 and ur(kB-CODATA)=1.7 × 10 -6. The new relative uncertainty approaches the target value of 1 × 10 -6 set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin. © 2011 The Royal Society.


PubMed | Laboratoire Communications Of Metrologie Lne Cnam Lcm
Type: Journal Article | Journal: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences | Year: 2011

The paper reports a new experiment to determine the value of the Boltzmann constant, k(B)=1.3806477(17)10(-23) J K(-1), with a relative standard uncertainty of 1.2 parts in 10(6). k(B) was deduced from measurements of the velocity of sound in argon, inside a closed quasi-spherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of k(B) is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k(B)(new)/k(B_CODATA)-1)=-1.9610(-6), where the relative uncertainties are u(r)(k(B)(new))=1.210(-6) and u(r)(k(B_CODATA))=1.710(-6). The new relative uncertainty approaches the target value of 110(-6) set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin.

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