International and National Journals
U. Pogliano
Evaluation of the uncertainties in the measurement of distorted power by means of the IEN sampling system
IEEE Transactions on Instrumentation and Measurement, Vol. 55, no. 2, pp. 620-624, 2006.
A method for the uncertainty evaluation in the measurement of power in distorted signals is described. The power is obtained by a sampling system, which acquires the voltage and current and computes the power from the harmonic components obtained by the best fit. An equivalent algorithm is applied to derive a simplified relation between the correlation matrix of the harmonics and that of the samples. The uncertainties are then evaluated by a model of the uncertainty of a single sample given by the manufacturer of the sampling voltmeters.
U. Pogliano, G. C Bosco, M. Lanzillotti
Generalized Automatic System for AC/DC Transfer, AC Voltage and AC Current Measurements
IEEE Transactions on Instrumentation and Measurement, Vol. 55, no. 5, pp. 1747-1751, 2006.
A generalized system for automatic ac/dc transfer, ac voltage, and ac current measurement has been built, which consists in a set of programmable instruments and a proper software. The hardware of the system is configurable and the software can be arranged for a wide range of operative needs. The system has been tested for the measurement repeatability and for the compatibility with measurements performed by previous systems. The result of such investigations is satisfactory for both these characteristics and the system can now be utilized for the almost automatic operation in a large variety of calibrations.
A. Sosso, V. Lacquaniti, D. Andreone, R. Cerri, A.M. Klushin
Tests of operating conditions for metrological application of HTS Josephson arrays
Journal of Physics: Conference Series (7th European Conference on Applied Superconductivity), Vol. 43, pp. 1370-1372, 2006.
We report on an experimental study of metrological properties of High Temperature Superconductor arrays, made of shunted bicrystal YBCO Josephson junctions, to assess their accuracy. A detailed analysis of measurement errors is presented, mainly based on a direct comparison of an HTS array against a low temperature array. Owing to the high sensitivity of the comparison, we were able to measure the changes in the HTS array voltage on a step at nanovolt level. A precise estimate of the dependence of the HTS array step width on operating conditions was obtained. Differences were observed with respect to the results provided by the usual, low sensitivity, techniques, confirming that the method we adopted is necessary in the study of HTS arrays for metrology. The high sensitivity analysis was applied in the derivation of the temperature dependence of the critical current as well, providing some insights on the behaviour of the HTS array.
L. Oberto, F. Pennecchi
Estimation of the modulus of a complex-valued quantity
Metrologia, Vol. 43, pp. 531-538, 2006.
This paper analyses two possible estimators for the modulus of a complex-valued quantity. The case of uncorrelated and normally distributed real and imaginary parts is treated. The expectations of the two estimators are calculated for varying parameters of the two normal distributions. They are derived analytically, when possible, otherwise numerically by means of Monte Carlo simulations. Studying the statistical behaviour of the two estimators, it can be deduced which represents the best choice, depending on the specific experimental context. The relationship between the second estimator and the maximum likelihood estimator for a Rayleigh distribution is also presented. Examples from the metrological and physical fields are provided in order to compare the considered estimation methods.
F. Pennecchi, L. Callegaro
Between the mean and the median: the Lp estimator
Metrologia, Vol. 43, pp. 213-219, 2006.
This paper presents the class of the L p(least power) estimators and their main properties. Particular estimators belonging to such a class are well known in metrology, like the sample median, the sample mean and the mid-range (that is the L p estimator with p = 1, 2, ∞, respectively), whereas the L p estimator with generic p is not yet applied within the metrological context. Thanks to robustness and efficiency properties intermediate between those of the sample mean and the sample median, the L p estimator with 1 < p < 2 (in particular, with p = 1.5) appears suitable for the statistical processing of experimental results. Application examples of the L p estimator to international intercomparison data processing are reported.
L. Callegaro
Unified derivation of Johnson and shot noise expressions
American Journal of Physics, no. 74, pp. 438-440, 2006.
Shot noise and Johnson noise in electrical circuits are usually introduced by referring to completely separate physical models and derivations. We derive Johnson and shot noise expressions from the same physical model, an ideal tunnel junction, to show the deep connection between the two types of noise. The derivation uses concepts of quantum mechanics, thermodynamics, and signal processing.
L. Callegaro, M. Pisani
Practical realization of Nyquist's gedanken experiment
Applied Physics Letters, Vol. 89, p. 034105, 2006.
If two noisy electrical dipoles are connected with an electric line, noise power can flow through the line. Such power can be measured, in the audio frequency range, with a wattmeter with spectral display capabilities. If the dipoles are two equal resistors in thermodynamic equilibrium, the power depends exclusively on the temperature difference, giving a differential noise thermometry method. If the dipoles are at the same temperature, but one is out of thermodynamic equilibrium (because of a flowing dc current), noise power depends on excess noise only, and it is possible to measure excess noise far below Johnson noise threshold.
A. Sosso, V. Lacquaniti, D. Andreone, R. Cerri, A. M. Klushin
Study and operating conditions of HTS Josephson arrays for metrological application
Physica C: Superconductivity and its applications, Vol. 435, no. 1-2, pp. 125-127, 2006.
We report an experimental study of metrological properties of high-temperature superconductor arrays, made of shunted bicrystal YBCO Josephson junctions. The work is mainly based on a direct comparison against a low temperature array. Owing to the high sensitivity of the measurements, we observed at nanovolt level the changes in the HTS array voltage on a step. A precise estimate of the dependence of the HTS array step width on operating conditions was obtained. Differences were observed with respect to the results of low sensitivity techniques, confirming that our method is necessary in the study of HTS arrays for metrology. The high sensitivity analysis was also applied in the derivation of the temperature dependence of the critical current, providing insights on the behavior of the HTS array.
P. P. Capra, F. Galliana
Sistema per la taratura di pinze amperometriche in c. a.
Tutto Misure, n. 1, pp. 62-64, 2006.
In questo articolo si descrive il sistema di misura sviluppato all'IEN per la taratura di pinze amperometriche in corrente alternata (50 Hz) nel campo 0-1500 A. Il sistema è costituito da un trasformatore di alimentazione con un circuito secondario che in configurazione parallela può fornire una corrente fino a 1500 A. L'avvolgimento primario è controllato da un VARIAC. La corrente fornita viene misurata con un trasformatore di corrente campione, un resistore campione da 50 mΩ e un multimetro digitale. La pinza amperometrica viene applicata ad un filo di rame di opportuna sezione e montata su di un supporto oscillante. I livelli di riferibilità vanno da 1.9×10-3 a 50 A a 4.2×10-3 a 1500 A.
G. Marullo Reedtz
Prima riunione del Comitato Qualità di Euromet
Tutto Misure, n. 3, p. 235, 2006.
Il Comitato Tecnico EUROMET sulla qualità, evoluzione del gruppo di lavoro QS-Forum, si è riunito per la prima volta a Malta nel febbraio 2006. Oltre alla presentazione dei sistemi qualità di vari laboratori metrologici nazionali, sono state trattati alcuni temi generali, quali l'applicazione della guida ISO 34 per la produzione di materiali di riferimento e le modalità per l'organizzazione di peer reviews.
L. Brunetti, L. Oberto, P. Terzi, M. Sellone
Valori di consenso nel primo confronto nazionale inter-laboratorio potenza in alta frequenza
Tutto Misure, n. 4, pp. 293-296, 2006.
Allo scopo di verificare le effettive capacità metrologiche dei laboratori accreditatati nel campo dell'alta frequenza dal Servizio di Taratura in Italia, è stato promosso un confronto inter-laboratorio avente misure di potenza elettromagnetica per specifico oggetto. L'esercizio è consistito nella taratura di un wattmetro ad alcune frequenze comprese nella banda 50 MHz - 26.5 GHz, contemplando l'uso di un sensore in linea di trasmissione coassiale da 7 mm con connettore tipo PCN ed un sensore in linea coassiale da 3.5 mm con connettore tipo PC3.5. Si descrivono alcuni dettagli tecnici del confronto con particolare riguardo alla procedura di analisi dei risultati adottata dall'INRiM in qualità di laboratorio pilota.
Conference Proceedings
L. Callegaro, V. D'Elia
A current source for picoamperemeter calibration
Proceedings of Instrumentation and Measurement Technology Conference (oral session), pp. 955-958, Sorrento (Italy), April 2006.
A traceable current source for the calibration of low-current meters (picoamperemeters, electrometers) in the 100fA-100pA current range is here presented. It is based on a low-frequency trapezoidal wave generator, measured with a sampling voltmeter, which charges and discharges a gas-dielectric capacitor. The generated current is traceable to units of voltage, capacitance and time. The source will be employed to extend in the lower range the Italian national standard of dc current, and for the Italian participation in the EUROMET. EM-S24 international intercomparison. Being simple and inexpensive, the source can find application in secondary calibration laboratories.
U. Pogliano, G. Boella, D. Serazio
An investigation over superconductive inductive and capacitive components for high precision measurements
Proceedings of Instrumentation and Measurement Technology Conference, pp. 837-840, Sorrento (Italy), April 2006.
Superconductive inductive and capacitive components seem to be very appealing for many high precision measurements, because of their reduced dissipation. Some tests made at I.N.RI.M. have proved the possibility of building inductors with quality factor higher than some thousands in the acoustic frequency band using copper clad Nb-Ti wiress. However, the best performances have been obtained with pure Nb wire, even with some connection problems.
L. Callegaro, V. D'Elia
A current source for the evaluation of low-current meters
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
The need for accurate calibration of current meters in the picoampere range is continuously increasing. A traceable current source for calibration of meters in the 100 fA - 100 pA current range is here presented. The source is based on a low-frequency generator ramp generator, which charges and discharges a gas-dielectric capacitor. Current traceability is given by the measurement of voltage parameters with a sampling voltmeter, and by calibration of the capacitor at audio frequency. The source has been employed in the EUROMET.EM-S24 "Comparison of small current sources" supplementary comparison.
L. Callegaro, G. C. Bosco, F. Cabiati, V. D'Elia
Evolution of the Italian national standard of inductance
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
The realization of inductance unit and scale at the Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), the Italian national metrology institution, has evolved during the last 35 years. An historical survey of realization and dissemination methods, and a graphical analysis of the stability of the mantained national inductance standard, is here reported. Results confirm the high stability of artifact standards.
E. Vremera, C. Fosalau, L. Brunetti
Design requirements for sensors based on amorphous wires resulting from measurements and simulation
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
Amorphous wires are attractive components for sensors and micro-sensors realization. The negative factors that affect the behaviour of these sensor types must be however put in evidence and cancelled throughout adequate tools. The characteristics of the sensing element can be carried-out starting from the measurement results. A model for the sensing element of a magneto-impedance device is obtained and is used in a PSPICE simulation next step. The paper presents the results obtained at high-frequency, together the mathematical modelling of the sensitive part. In addition there are and the requirements to fulfill in the design of this kind of sensors.
L. Brunetti, L. Oberto, M. Sellone
Reference value in high frequency power comparisons
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
According to the modern trend, the reference value of a measurement comparison among laboratories is established considering the contribution of all the participants appropriately. The main problem is deciding whether the data are consistent or they have to be discarded because of the evidence that the measured value is too different from the expected one. In this paper, the problem of the data rejection is analyzed for a specific comparison concerning microwave power measurements and a decision algorithm is presented.
L. Brunetti, L. Oberto, E. Vremera
Calibration concept of modern power meters
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
The power is the most important electromagnetic quantity from the metrological point of view, and for this reason the calibration techniques of high frequency power meters require a specific attention. Literature still refers to power meters of bolometer type, instruments that are mainly used almost only in the primary laboratories. Definitions, procedures, and calibration techniques elaborated for this instrument type must be adjusted before being applied to actual power meters, which work on different principles. Otherwise, inconsistent calibration results may be produced. This paper is aimed to ease the work of the laboratories that perform power meter calibrations from dc to 50 GHz, by elaborating on some technical aspect not well considered in the specialized literature.
U. Pogliano
A system for calibration of power quality analysers
Proceedings of the XVIII IMEKO World Congress (oral session), Rio de Janeiro (Brazil), September 2006 (on cd rom).
Power quality analyzers utilized in the measurements have to be calibrated and a system for both developing proper methodologies and for their calibration is now under development at I.N.RI.M. The system can supply two synchronized voltage and current signals, with the possibility of generating both calibrated periodic distorted waveforms and suitable preprogrammed aperiodic events.
P. P. Capra F. Galliana, D. Serazio
Miglioramento dei livelli di riferibilità nell'alta resistenza in corrente continua per mezzo della realizzazione di un resistore del tipo Hamon 10 × 100 m automatizzato e dotato di guardia attiva
Atti del XXIII Congresso Nazionale "Gruppo Misure Elettriche ed Elettroniche (GMEE 2006)", pp. 5-6, L'Aquila (Italy), settembre 2006.
Presso l'INRIM è stato progettato, costruito ed ora è in fase di caratterizzazione un resistore di trasferimento del tipo Hamon composto da dieci resistori di valore nominale 100 MΩ dotato di guardia attiva. Con questo campione si ritiene che si potranno migliorare i livelli di riferibilità del campione da 1 GΩ mantenuto presso l'INRIM dagli attuali 8×10-6 a meglio di 4×10-6.
L. Callegaro, V. D'Elia
Estensione del campione nazionale di corrente continua al dominio 100 fA - 100 pA
Atti del XXIII Congresso Nazionale "Gruppo Misure Elettriche ed Elettroniche (GMEE 2006)", pp. 13-14, L'Aquila (Italy), settembre 2006.
Per estendere il campione nazionale di corrente elettrica in regime continuo verso le piccole correnti, è stata realizzata una sorgente di corrente continua operante nel dominio 100 fA - 100 pA, riferibile ai campioni nazionali di capacità elettrica e tensione elettrica. La sorgente è stata impiegata nel confronto internazionale EUROMET-EM.S24 e verrà utilizzata per le tarature di elettrometri, picoamperometri e dosimetri provenienti dai centri di taratura.
L. Callegaro, V. D'Elia
Il campione nazionale di induttanza: 1970-2005
Atti del XXIII Congresso Nazionale "Gruppo Misure Elettriche ed Elettroniche (GMEE 2006)", pp. 15-16, L'Aquila (Italy), settembre 2006.
La realizzazione del campione nazionale e della scala di induttanza presso l'Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), oggi Istituto Nazionale di Ricerca Metrologica (INRIM), si è evoluta notevolmente nel corso degli ultimi trentacinque anni, ma il mantenimento è affidato tuttora allo stesso insieme di campioni materiali. Viene presentata l'evoluzione storica dei metodi di realizzazione e disseminazione, e un'analisi della stabilità del campione mantenuto.
U. Pogliano
Un sistema per la generazione di segnali aperiodici per la taratura di analizzatore di power quality
Atti del XXIII Congresso Nazionale "Gruppo Misure Elettriche ed Elettroniche (GMEE 2006)", pp. 215-216, L'Aquila (Italy), settembre 2006.
Gli analizzatori di power quality devono essere tarati in base di una catena di riferibilità. Attualmente presso l'I.N.RI.M. si sta sviluppando un sistema, che unitamente ad opportune metodogie, consentirà il loro riferimento ai campioni nazionali. Il sistema fornisce un segnale di tensione e uno di corrente sincronizzati tra di loro, con la possibilità di generare sia segnali periodici distorti e sia eventi aperiodici programmati.
Technical Reports
L. Brunetti, L. Oberto, P. Terzi
Confronto nazionale interlaboratorio SIT.AF-01. Potenza AF in linea di trasmissione coassiale da 50 MHz a 26,5 GHz
Rapporto Tecnico INRIM n. 6, marzo 2006.
Nel rapporto sono riportati i risultati del primo ciclo nazionale di potenza AF. I dati di misura sono relativi a 12 laboratori di cui 10 già accreditati SIT per la suddetta grandezza e 2 in fase di accreditamento. L'intento di questo confronto interlaboratorio è quello di verificare le capacità metrologiche per la grandezza potenza in alta frequenza (AF) nella banda di frequenze coperta dalla linea di trasmissione coassiale da 7 mm (50 MHz a 18 GHz) e nella banda di frequenze coperta dalla linea da 3.5 mm (50 MHz a 26,5 GHz).
L. Callegaro, V. D'Elia
EUROMET.EM-S24 Comparison of small current sources: INRIM participation report
INRIM Technical Report no. 15, June 2006.
INRIM participated in the Euromet Supplementary Comparison "Comparison of small current sources", EUROMET-EM.S24. The pilot laboratory is circulating two travelling standards (commercial picoammeters) to be calibrated at four nominal current values (±95 fA, ±0.95 pA, ±9.5 pA, ±95 pA). INRIM measured the standards during March 2006, by employing a novel current source traceable to national standards of dc voltage and capacitance. The following reports the results of the calibration and the corresponding evaluation of uncertainty, with explaining notes.
L. Brunetti, L. Oberto, P. Terzi
Confronto nazionale interlaboratorio SIT.AF-01. Potenza AF in linea di trasmissione coassiale da 50 MHz a 26,5 GHz
Rapporto Tecnico SIT, SIT.AF-01/06, marzo 2006.
Nel rapporto sono riportati i risultati del primo ciclo nazionale di potenza AF. I dati di misura sono relativi a 12 laboratori di cui 10 già accreditati SIT per la suddetta grandezza e 2 in fase di accreditamento. L'intento di questo confronto interlaboratorio è quello di verificare le capacità metrologiche per la grandezza potenza in alta frequenza (AF) nella banda di frequenze coperta dalla linea di trasmissione coassiale da 7 mm (50 MHz a 18 GHz) e nella banda di frequenze coperta dalla linea da 3.5 mm (50 MHz a 26,5 GHz).
C. Cassiago, G.C. Bosco
Programma di gestione del sistema di taratura in tensione continua di calibratori multifunzione
Rapporto Tecnico INRIM n. 43, dicembre 2006.
Il presente rapporto descrive il programma di controllo del sistema automatico di taratura in tensione continua dei calibratori multifunzione Datron 4808 e Fluke 5700A e 5720A, utilizzati come campioni di lavoro nel laboratorio della stazione automatica di taratura degli strumenti multifunzione programmabili.