International and National Journals

G. Cavagnero, G. Mana, E. Massa
Aberration effects in two-beam laser interferometers
Journal of Optical Society of America A, Vol. 23, pp. 1951-1959, 2006.

In displacement measurements by two-beam interferometers, the wavefront curvature of a laser beam causes systematic increase of the fringe period. This increase depends on beam collimation: It is null for a plane wave and proportional to the squared divergence of the beam. With interfering beams not perfectly recombined an additional fringe-period error is caused, with the effect of counteracting and also of compensating for and prevailing over the usual error. This paper describes this unsuspected effect and gives a correction equation.

M. G. Cox, C. Eio, G. Mana, F. Pennecchi
The generalized weighted mean of correlated quantities
Metrologia, Vol. 43, pp. S268-S275, 2006.

An analysis is presented of the generalized weighted mean of a set of quantities, some or all of which may be correlated, and the variance associated with that mean. Cases covered specifically are (a) two correlated quantities, (b) a general number of quantities, two of which are correlated, and (c) a general number of quantities, all of which are correlated. For (c), two instances are treated, viz., where the quantity variances are equal and unequal. Consistency of the data representing realizations of the quantities concerned is shown to be important in terms of appreciating the results obtained.

S. Lorefice, A. Malengo
Calibration of hydrometers
Measurement Science and Technololy, no. 17, pp. 2560-2566, 2006.

After a brief description of the different methods employed in periodic calibration of hydrometers used in most cases to measure the density of liquids in the range between 500 kg m^-3and 2000 kg m^-3, particular emphasis is given to the multipoint procedure based on hydrostatic weighing, known as well as Cuckow's method. The features of the calibration apparatus and the procedure used at the INRiM (formerly IMGC-CNR) density laboratory have been considered to assess all relevant contributions involved in the calibration of different kinds of hydrometers. The uncertainty is strongly dependent on the kind of hydrometer; in particular, the results highlight the importance of the density of the reference buoyant liquid, the temperature of calibration and the skill of operator in the reading of the scale in the whole assessment of the uncertainty. It is also interesting to realize that for high-resolution hydrometers (division of 0.1 kg m^-3), the uncertainty contribution of the density of the reference liquid is the main source of the total uncertainty, but its importance falls under about 50% for hydrometers with a division of 0.5 kg m^-3and becomes somewhat negligible for hydrometers with a division of 1 kg m^-3, for which the reading uncertainty is the predominant part of the total uncertainty. At present the best INRiM result is obtained with commercially available hydrometers having a scale division of 0.1 kg m^-3, for which the relative uncertainty is about 12×10^-6.

W. Bich, M. G. Cox, P. M. Harris
Evolution of the "Guide to the Expression of Uncertainty in Measurement"
Metrologia, Vol. 43, no. 4, pp. S161-S166, 2006.

A number of Joint Committees of the Bureau International des Poids et Mesures and other international organizations carry out particular tasks of common interest. The Joint Committee for Guides in Metrology (JCGM) has amongst its tasks the promotion of the "Guide to the Expression of Uncertainty in Measurement" (GUM), the preparation of further documents for its broad application, and revision and promotion of the use of the "International Vocabulary of Basic and General Terms in Metrology". This paper summarizes the documents relating to the GUM planned by JCGM.

W. Bich, M. G. Cox
Special issue on Statistical and Probabilistic Methods for Metrology
Metrologia, Vol. 43, no. 4, foreword 2006.

This special issue of Metrologia is the first that is not devoted to units, or constants, or measurement techniques in some specific field of metrology, but to the generic topic of statistical and probabilistic methods for metrology.

W. Bich, L. Callegaro, F. Pennecchi
Non-linear models and best estimates in the GUM
Metrologia, Vol. 43, pp. S196-S199, 2006.

A non-linear function of a sample average is different from the average of that function evaluated for each element of the sample. However, in the Guide to the expression of Uncertainty in Measurement (GUM) the second approach to calculating an average is considered potentially preferable to the first in order to obtain a measurand estimate. In this paper the issue is discussed, and it is shown that the second approach is inconsistent with the GUM framework. However, it is indeed preferable for input quantities having an intrinsically random behaviour. We comment the approach adopted in this respect in Supplement 1 of the GUM and show that it is consistent with the first method.

W. Bich
The Guide to the expression of uncertainty in measurement: where do we stand?
ISO Focus, Vol. 3-10, p. 25, 2006.

A brief history of the JCGM-WG1 and a summary of the actions undertaken in the field of uncertainty of measurement.

W. Bich
Newton's Laws, Planck's Principle, and Metrology in Chemistry
Accreditation and Quality Assurance, no. 11, pp. 638-639, 2006.

This quasi-serious joke is an attempt to interpret human behaviour in terms of Newton's Laws of motion and Planck's Principle, with reference to the interaction of chemistry with "classical" metrology.

K. Fujii, H. Bettin, A. Peuto, Kyung-Ho Chang, P. Richard, C. Jacques, C. Matilla Vicente, L. Omar Becerra
Final report on CIPM key comparison CCM.D-K1: density measurements of a silicon sphere
Metrologia, Vol. 43, no. 1A, 07007 (Technical Supplement 2006).

This report describes the results of a CIPM key comparison of solid density measurements, which was carried out through July 2001 to May 2003. This CIPM key comparison, designated as CCM.D-K1, was coordinated by the National Metrology Institute of Japan (NMIJ, Japan), Swiss Federal Office of Metrology and Accreditation (METAS, Switzerland), and National Research Council Canada (NRC, Canada). These three National Metrology Institutes (NMIs) formed a pilot group to determine the technical protocol for this key comparison. A total of eight NMIs, namely NMIJ, Physikalisch-Technische Bundesanstalt (PTB, Germany), Istituto di Metrologia "G. Colonnetti" (IMGC, Italy), Korea Research Institute of Standards and Science (KRISS, Korea), METAS, NRC, Centro Espanol de Metrologia (CEM, Spain), and National Center of Metrology (CENAM, Mexico), participated in this key comparison. A 1 kg single-crystal silicon sphere, prepared by NMIJ, was circulated to each of the NMIs as a travelling standard. Each NMI determined the mass, volume and density of the travelling standard with respect to the mass and the solid density standards of each NMI, by mass measurement and hydrostatic weighing. The reference value of the density was determined with a relative expanded uncertainty of 2.9 × 10⁷. When the degree of equivalence was evaluated by differences from the reference value, the differences for the mass, volume, and density were almost equal to or less than the expanded uncertainties of the differences, showing a good equivalence of the capabilities for the solid density measurement at the participating NMIs.

R. Arias, M. Maldonado, J. Wright, C. Jacques, C. Lachance, P. Lau, H. Többen, G. Cignolo, S. Lorefice, J. Man, V. Y Aibe
Results of the key comparison CCM.FF-K4 for volume of liquids at 20 L and 100 mL
Metrologia, Vol. 43, no 1A, 07005 (Technical Supplement 2006).

This report describes the result of a key comparison CCM.FF-K4 for volume of liquids at 20 L and 100 mL. Eight NMIs (CENAM-MX, NIST-US, NRC/MC-CA, SP-SE, PTB-DE, IMGC-IT, NMIA-AU and INMETRO-BR), took part in this project coordinated by the Mexican CENAM. The transfer standard is comprised of three 20 L metallic pipettes and six 100 mL glass pycnometers. During the test phase, both "single-lab" and "multi-lab" reproducibility data showed to be satisfactory.

M. Onorato, G. M. Di Cicca, G. Iuso, P. G. Spazzini, R. Malvano
Turbolent boundary layers and their control: quantitative flow visualization results
Transition and Turbolence Control (M. Gad-el-Hak, Her Mann Tsai Eds.), pp. 247-282, World Scientific 2006.

Results obtained by applying PIV to canonical turbulent boundary layers and to wall flows under the action of external forcing produced by spanwise wall oscillations are shown and analyzed. In particular, results obtained at the Aerodynamic Laboratory of the Politecnico di Torino are discussed, with reference, where it is possible, to results produced in other laboratories. For both flows, PIV images in planes streamwise-normal and parallel to the wall are analyzed.

S. Lorefice
Seminario sulle misure di densità di solidi e liquidi
Tutto Misure, n. 2, p. 157, 2006.

La sintesi dei lavori e le conclusioni del "210. PTB Seminar - Precision Density Measurements of Solids and Liquids" tenutosi in Braunschweig (Germany)- October 24 to 26, 2005 sono l'argomento di questa breve presentazione.

G. Cignolo, P. Spazzini
La riunione annuale Euromet TC "Flow"
Tutto Misure, n. 3, pp. 236-238, 2006.

Vengono presentati gli argomenti discussi nella riunione tenuta a Lisbona presso il Laboratorio Centrale di Metrologia (LCM) dell' Instituto Português da Qualidade (IPQ). Si tratta di confronti internazionali di misure e di campioni, di progetti comuni e dell'elaborazione delle linee guida (roadmaps) a medio e lungo termine da perseguire nella ricerca sulle misure di quantità e portate di liquidi e gas.

G. Cignolo, P. Spazzini
La riunione annuale dell'EUROMET TC "Flow"
Eidos, n. 2, pp. 10-13, 2006.

Vengono presentati gli argomenti discussi nella riunione tenuta a Lisbona presso il Laboratorio Centrale di Metrologia (LCM) dell' Instituto Português da Qualidade (IPQ). Si tratta di confronti internazionali di misure e di campioni, di progetti comuni e dell'elaborazione delle linee guida (roadmaps) a medio e lungo termine da perseguire nella ricerca sulle misure di quantità e portate di liquidi e gas.

G. Mana
La determinazione della costante di Avogadro
Tutto Misure, n. 2, pp. 144-145, 2006.

Conference Proceedings

W. Bich, F. Pennecchi
Developments in uncertainty evaluation: the activity of JCGM/WG1
Proceedings of the International Workshop IUPAC-APAT, (invited talk), pp. 117-126, Royal Chemical Society Publishing, London (U.K.) 2006.

In this paper the recent developments in the uncertainty evaluation made by the Joint Committee for Guides in Metrology (JCGM) are outlined. The JCGM/WG1 is preparing two specific supplements to the GUM addressing two specific cases:

1. when a coverage interval is required at a stipulated coverage probability;
2. when more than a measurand are involved in the measurement.

This paper, while describing the two documents, outlines the techniques proposed to address the mentioned issues. An example is provided concerning metrology in chemistry.

S. Lorefice, A. Malengo
Hydrostatic weighing system at the INRIM for calibrating hydrometers
Proceedings of the IMEKO XVIII World Congress, Rio de Janeiro (Brazil), September 2006 (on cd rom).

Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we present the new hydrostatic weighing system developed at the INRiM, formerly IMGC - CNR, for the calibration of hydrometers in the range 500 kg.m^-3 to 2000 kg.m^-3. The apparatus which uses a method to automatically align specific scale-marks for the calibration of hydrometers makes easy all procedure of calibration. It consists of a vision system, a stepping motor, and software to control the system. The vision system is composed of a CCD camera and a frame grabber, and is used to acquire images. The performance of all apparatus is illustrated by the assessment of the uncertainty of calibration for some kind of hydrometers.

W. Bich, F. Pennecchi
The GUM, guide to the expression of uncertainty in measurement, and related documents. Present status and future developments
Proceedings of the IMEKO XVIII World Congress, Rio de Janeiro (Brazil), September 2006 (on cd rom).

In this paper the recent developments in the uncertainty evaluation are outlined, by describing the activity of the Joint Committee for Guides in Metrology-Working Group 1 on the Expression of Uncertainty in Measurement, and the documents that this WG is preparing on uncertainty.

H. Baumann, G. Cignolo, M. Clausen, R. Goria
EUROMET Project 852: a comparison between Italian and Swiss gas flow standards in the range 0.3 to 25 m³/h
Proceedings of the 6^th ISFFM (International Symposium on Fluid Flow Measurement), Querétaro (Mexico), May 2006 (on cd rom).

An interlaboratory comparison of four primary standard gas provers was carried out between the Italian and Swiss National Measurement Institutes (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 lower flows some discrepancies occurred, whose causes are identified and discussed. The results confirm the improved accuracy of the large piston provers pioneered by both laboratories, if compared to bell provers, a couple of which were also tested.

R. Malvano, P. G. Spazzini, A. Piccato, M. Onorato
A rotating ring for low-speed anemometer testing
Proceedings of the 6^thISFFM (International Symposium on Fluid Flow Measurement), Querétaro (Mexico), May 2006 (on cd rom).

The present paper is aimed at describing the main low-speed anemometric test device of INRIM. This device consists of a 3.5 m long rotating arm which carries the instrument to be tested or calibrated. Details about the test rig device are provided together with a discussion about uncertainty sources and uncertainty evaluation.

A. Piccato, R. Malvano, P. G. Spazzini
A translating ring for low-speed anemometer testing
Proceedings of the 6^thISFFM (International Symposium on Fluid Flow Measurement), Querétaro (Mexico), May 2006 (on cd rom).

The low air-speed primary standard of INRIM called Towing Tank is described and its measurement uncertainty is discussed, giving details about its measurement chain. The Towing Tank is a 30 m long facility, whose useful measurement range is 0.05 m/s <U < 1.20 m/s, with a best measurement uncertainty equal to 2% at the maximum speed. This facility is complementary to the companion test device (the Rotating Arm [1]), whose motion is rotational and continuous, while in the Towing Tank motion is linear, but limited in time. In both facilities speed measurement is traceable to length and time primary standards.

V. Diederichs, M. Lapolla, L. Lorefice, R. Malvano, B. Pralio, P. G. Spazzini, M. Onorato, C. Haigermoser, L. Vesely
PIV Study Near Wall Organized Motions
25^th International Council of the Aeronautical Sciences (ICAS 2006), Hamburg (Germany), September 2006.

The strong development of Particle Image Velocimetry in the last few years has opened a new field for the experimental study of turbulent flows. The main importance of PIV with respect to classical point measurement techniques is the ability of producing instantaneous maps of the velocity field, giving information about organized motions and their relation to the skin friction growth and turbulence production. At the Politecnico di Torino Aerodynamic Laboratory a large number of students and researchers is involved in PIV studies on the dynamics of the organized motions in near wall turbulent flows and on their control [6, 7, 9, 10, 15]. In the present paper swirling motions in streamwise-wall-normal planes are described, with reference in particular to the rarely commented positive swirling motions.

Technical Reports

L. Ferroglio
Considerations on the design of an X-ray interferometer
INRIM Technical Report no. 9, March 2006.

We will show how the mechanical behaviour of the analyzer of the silicon 28 interferometer is affected by various anomalies such as surface energy, friction on the footholds and bad positioning of the interferometer foot with respect to their optimal position. Additionally, in order to access the performances of the software tool used for the simulations (FEMLAB), we will compare the numerical solution of the deformation of a rod with the analytic solution derived from elasticity theory.

A. Rivetti, G. Martini, G. La Piana, F. Alasia
Thruster PVN02 e regolatore di pressione PV02: dati costruttivi e tecniche di montaggio
Rapporto Tecnico INRIM n. 10, aprile 2006.

I due dispositivi PVN02 (thruster) e PV02 (regolatore di pressione) sono i componenti essenziali del sistema di propulsione per satelliti sviluppato da INRIM su contratto con la Divisone di Firenze di AAS-I (Alcatel Alenia Space - Italia), nell'ambito della commessa di sviluppo ESA denominata Cold gas. Il rapporto descrive il principio di funzionamento dei due dispositivi e contiene i dati di progetto, le caratteristiche costruttive dei singoli elementi, le procedure di assemblaggio e di verifica funzionale.

L. Ferroglio
Deformazione dei piani reticolari di un interferometro a raggi X per effetto della tensione superficiale sulle facce del cristallo analizzatore
Rapporto Tecnico INRIM n. 11, aprile 2006.

L'energia immagazzinata sulla superficie del cristallo analizzatore di un interferometro a raggi X origina una sollecitazione superficiale ineliminabile sulle facce del cristallo. Di conseguenza, il reticolo cristallino risulta deformato, la deformazione dipendendo, in linea di principio, dalla conformazione geometrica del cristallo e dall'entità della tensione superficiale. Vengono qui riportati i risultati di una simulazione agli elementi finiti volta a quantificare la conseguente variazione di passo reticolare.

G. La Piana, A. Rivetti, G. Martini
Apparecchiatura a micro-controllore per l'esecuzione della procedura di avvio di un thruster per satelliti con attuatori piezo
Rapporto Tecnico INRIM n. 12, maggio 2006.

Sono descritte due apparecchiature elettroniche realizzate per assicurare il controllo dei thrusters piezo-elettrici sviluppati con AAS-I (Firenze) e destinate ad essere utilizzate da ESA per le missioni LISA e GAIA. La prima apparecchiatura realizza la procedura di recupero dei giochi del thruster all'avvio senza che vengano esercitate spinte indesiderate. La seconda è utilizzata per eseguire variazioni di spinta con rampe programmabili e ripetibili.

G. Cignolo, A. Piccato
Measurements carried out at I.N.RI.M. during Euromet project 806
INRIM Technical Report no. 38, November 2006.

EUROMET 806 is an intercomparison Project between primary standard facilities for measurement of low-pressure flows of nitrogen or air in the range 0.1 L/min to 25 L/min, in which not less than 11 European National Measurement Institutes are participating. The Report gives essential information about the Project, the transfer standards adopted (a couple of Laminar Flow Elements), the primary standards used at INRIM during 2006 for their calibration, as well as about measurement conditions and results. Hard copies of the files of descriptions, results and Calibration Certificates submitted to the pilots (NEL, UK, and EIM, Greece) are appended as Annexes and commented.

G. Mana, E. Massa
Note on the confirmation of the INRIM and PTB determinations of the Si lattice parameter
INRIM Technical Report no. 41, December 2006.

The natural Si d₂₂₀ lattice spacing data are being considered for inclusion in the 2006 CODATA adjustment. The CODATA Task Group decided to include the December 2004 INRIM value from WASO 4.2a crystal of the PTB and the 2005 INRIM value from MO*4 crystal of the INRIM. This report supplies additional information which is necessary for the calculation of the covariance of these values.