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NOTIZIE BREVI

Ricerca e Sviluppo nel campo delle Misure e della Strumentazione
R&D in Measurement and Instrumentation

A cura della Redazione


E-mail:

franco.docchio@ing.unibs.it

SUMMARY
This article contains an overview of relevant achievements of Italian R&D groups, in the field of measurement science and instrumentation, at both theoretical and applied levels. Sources of information are the main Measurement-related journals, as well as private communications by the authors. Industries are the main targets of this information, as it may be possible to find stimuli towards Technology Transfer.

RIASSUNTO
L’articolo contiene una panoramica dei principali risultati scientifici dei Gruppi di R&S Italiani nel campo della scienza delle misure e della strumentazione, a livello sia teorico sia applicato. Fonte delle informazioni è costituita dalle principali riviste di misure e da comunicazioni private degli autori. Le industrie sono i primi destinatari di queste notizie, poiché i risultati di ricerca riportati possono costituire stimolo per attività di Trasferimento Tecnologico.

RICERCA DI BASE IN METROLOGIA

Dall’INRiM la determinazione indiretta del punto del Rame

M. Battuello, M. Florio, F. Girard (Thermodynamics Division, Istituto Nazionale di Ricerca Metrologica - INRIM, Torino- E-mail: m.battuello@inrim.it): Indirect determination of the thermodynamic temperature of the copper point by a multi-fixed-point technique. Metrologia 47 (3), 231, 2010.
An indirect determination of the thermodynamic temperature of the fixed point of copper was made at INRIM by measuring four cells with a Si-based and an InGaAs-based precision radiation thermometer carrying approximated thermodynamic scales realized up to the Ag point. An average value TCu = 1 357.840 K was found with a standard uncertainty of 0.047 K. A consequent (T - T90)Cu value of 70 mK can be derived which is 18 mK higher than, but consistent with, the presently available (T - T90)Cu as elaborated by the CCT-WG4.

Determinazione della Costante di Boltzmann mediante la misura della velocità del suono dall’INRiM

M. Gavioso, G. Benedetto, P.A. Giuliano Albo, D. Madonna Ripa, A. Merlone, C. Guianvarc’h, F. Moro, R. Cuccaro (INRiM, Torino - E-mail: a.merlone@inrim.it): A determination of the Boltzmann constant from speed of sound measurements in helium at a single thermodynamic state. Metrologia 47 (4), 387, 2010.
We report on acoustic and microwave measurements made with a purified helium sample maintained close to a single thermodynamic state (Texp ~ 273.16 K, pexp ~ 410 kPa) within a 2.1 L volume stainless steel spherical cavity. From these measurements and ab initio calculations of the non-ideality and the refractive index of helium, we determine a value for the Boltzmann constant kB which is consistent with the recommended 2006 CODATA value:
(kB - k2006)/k2006 = (-7.5 ± 7.5) × 10-6
We discuss the current limits of the experiment and the prospects of a further reduction in the uncertainty associated with the determination of kB.

STRUMENTAZIONE DI MISURA

Algoritmo di campionamento adattivo per sensori wireless dal Politecnico di Milano

C. Alippi, G. Anastasi, M. Di Francesco, M. Roveri (Dip. Elettronica e Informatica, Politecnico di Milano - E-mail: roveri@elet.polimi.it): An Adaptive Sampling Algorithm for Effective Energy Management in Wireless Sensor Networks With Energy-Hungry Sensors. IEEE Trans. Instrum. Meas. 2, 335-344 (2010).
Energy conservation techniques for wireless sensor networks generally assume that data acquisition and processing have energy consumption that is significantly lower than that of communication. Unfortunately, this assumption does not hold in a number of practical applications, where sensors may consume even more energy than the radio. In this context, effective energy management should include policies for an efficient utilization of the sensors, which become one of the main components that affect the network lifetime. In this paper, we propose an adaptive sampling algorithm that estimates online the optimal sampling frequencies for sensors. This approach, which requires the design of adaptive measurement systems, minimizes the energy consumption of the sensors and, incidentally, that of the radio while maintaining a very high accuracy of collected data. As a case study, we considered a sensor for snow-monitoring applications. Simulation experiments have shown that the suggested adaptive algorithm can reduce the number of acquired samples up to 79% with respect to a traditional fixed-rate approach. We have also found that it can perform similar to a fixed-rate scheme where the sampling frequency is known in advance.

Microscopio ottico a campo vicino dal CNR

G. Longo, M. Girasole, G. Pompeo, R. Generosi, M. Luce, A. Cricenti (Ist. di Struttura della Materia, CNR, Roma - E-mail: longo@ism.cnr.it: A multipurpose hybrid conventional/scanning near-field optical microscope for applications in materials science and biology. Meas. Sci. Technol. 21 (4), 5502, 2010.
A hybrid conventional/scanning near-field optical microscope is presented. The instrument is obtained coupling an Olympus IX-70 inverted optical microscope with a SNOM head, to combine the versatility and ease of use of the conventional microscope with the high-resolution and three-dimensional reconstruction achieved by the SNOM. The head can be run in shear or tapping mode and is optimized to characterize soft, biological samples including living cells in physiological environment by including the SNOM in a cylindrical chamber that insulates it from external noise, while maintaining a controlled temperature and atmosphere.

La sicurezza delle banconote da Roma 3

G. Schirripa Spagnolo, L. Cozzella, C. Simonetti (Dip. Ingegneria Elettronica, Univ. degli Studi Roma Tre - E-mail: schirrip@uniroma3.it): Banknote security using a biometric-like technique: a hylemetric approach. Meas. Sci. Technol. 21 (5), 5501, 2010.
Banknote security is an issue that has led in the last decades to insert, inside the banknote itself, a very high number of controlling methods with the aim of verifying possible tampering attempts. In order to distinguish the false banknotes, sophisticated means (i.e. watermark, feel of the paper, raised print, metallic threads, quality of the printing, holograms, ultraviolet features, micro-lettering, etc.) are often used. The purpose of this paper is to show a new approach and related method to protect banknotes and to verify their originality, based on the idea of hylemetry (methodology conceptually similar to biometry) applied to banknotes. Specifically, the hylemetric feature used in this paper is the random distribution pattern of the metallic security fibers set into the paper pulp. The outcome of the proposed solution is to identify an original banknote using a binary sequence derived from the banknote itself.

Metodo di misura delle immagini mentali dalla Sapienza

M. D'Ercole, P. Castelli, A.M. Giannini (Dip. Psicologia 2), A. Sbrilli (Dip. Storia dell'Arte) (Univ. La Sapienza, Roma - E-mail: annamaria.giannini@uniroma1.it): Mental Imagery Scale: a new measurement tool to assess structural features of mental representations. Meas. Sci. Technol. 21 (5), 4019, 2010.
Mental imagery is a quasi-perceptual experience which resembles perceptual experience, but occurring without (appropriate) external stimuli. It is a form of mental representation and is often considered centrally involved in visuo-spatial reasoning and inventive and creative thought. Although imagery ability is assumed to be functionally independent of verbal systems, it is still considered to interact with verbal representations, enabling objects to be named and names to evoke images. In literature, most measurement tools for evaluating imagery capacity are self-report instruments focusing on differences in individuals. In the present work, we applied a Mental Imagery Scale (MIS) to mental images derived from verbal descriptions in order to assess the structural features of such mental representations. This is a key theme for those disciplines which need to turn objects and representations into words and vice versa, such as art or architectural didactics. To this aim, an MIS questionnaire was administered to 262 participants. The questionnaire, originally consisting of a 33-item 5-step Likert scale, was reduced to 28 items covering six areas: (1) Image Formation Speed, (2) Permanence/Stability, (3) Dimensions, (4) Level of Detail/Grain, (5) Distance and (6) Depth of Field or Perspective. Factor analysis confirmed our six-factor hypothesis underlying the 28 items.

Sonda tattile vibrante dall’Università di Catania

P. Brunetto, L. Fortuna, P. Giannone, S. Graziani, F. Pagano (Dip. Ingegneria Elettrica, Elettronica e dei Sistemi, Univ. di Catania - E-mail: lfortuna@diees.unict.it): A Resonant Vibrating Tactile Probe for Biomedical Applications Based on IPMC. IEEE Teans. Instrum. Meas. 59 (5), 1453-1462 (2010).
In this paper, a vibrating tactile probe is presented. The probe exploits the dependence of its resonant frequency on the varying load and hence on the contacted material. This methodology allows the recognition of different materials by observing the electrical quantities involved in the probe dynamics. More specifically, two ionic polymer-metal composite (IPMC) strips are used, one as actuator and one as sensor, that work together for the recognition of materials. The actuator forces the system into resonant conditions that, as stated before, change with the mechanical properties of the contacted material. The output signal produced by the IPMC sensor contains the information required for the estimation of the contacting material. The sensing capabilities could be exploited in various biomedical applications, such as catheterism and surgical resection of tumors. The model and the experimental validation of the proposed probe are reported. For each material, different surveys were collected to estimate the uncertainty of the resonant frequency and hence to obtain the characteristic diagram of the device along with its uncertainty. The reported results show that the developed probe can be used to distinguish among different materials.

Metodo di misura della distribuzione modale in fibre ottiche dal Politecnico di Torino

M. Olivero, G. Perrone, A. Vallan (Dip. Elettronica, Politecnico di Torino - E-mail: alberto.vallan@polito.it): Near-Field Measurements and Mode Power Distribution of Multimode Optical Fibers. IEEE Teans. Instrum. Meas. 59 (5), 1382 – 1388, 2010.
This paper analyzes the impact of some of the most common uncertainties arising in the computation of modal transfer function (MTF) and mode power distribution (MPD) in multimode fibers (MMFs). The evaluation of these parameters is carried out following a procedure that is currently being tested in the framework of an international round robin before becoming a recognized standard. MTF and MPD are key parameters for the determination of device excitation conditions and for the determination of whether a so called “equilibrium modal distribution” (EMD) has been achieved. The procedure evaluates these parameters by relying on near-field (NF) measurements, and this paper investigates the effects related to the nonlinearity of the camera used to grab the images, the image scale factor, and the defocus. In particular, the experimental assessment of these effects evidences the fault-tolerant properties of NF measurement provided some precautions are taken in the image acquisition and elaboration. Then, given the importance of operating the devices under an EMD, some typical techniques to achieve such a condition are reviewed, and an experimental realization of an effective mode conditioner is presented.

Taratura di strumenti per la misura di luminanza e illuminanza dall’Università di Padova

P. Fiorentin, A. Scroccaro (Dip. Ingegneria Elettrica, Univ. di Padova - E-mail: pietro.fiorentin@unipd.it): Detector-Based Calibration for Illuminance and Luminance Meters-Experimental Results. IEEE Trans. Instrum. Meas. 59 (5), 1375 – 1381, 2010.
The connection between illuminance and luminance measurements is considered to create a traceability link among a highly accurate illuminance meter, which is considered as an internal standard of the Photometric Laboratory, University of Padova, and other illuminance meters or photometric heads and luminance meters. After an introduction on the main involved definitions and equations linking the illuminance and the luminance measurements, this paper presents the instruments to which the procedures are applied and, at the end, results regarding the absolute calibration of the instruments under test, the check of their linearity, and the analysis of their spectral responsivity within the visible range. Following this way, this paper shows the main results in the connection among instruments devoted specifically to illuminance and luminance measurements. Then, it also introduces a comparison to other photometric heads, e.g., sensors that are part of more complex systems, like an integrating sphere for luminous flux measurement. In this last case, it has no significance to evaluate the difference between the absolute outputs, but it is interesting to compare the response of the two devices considering their linearity and their relative spectral response. A special section devoted to the evaluation of the spectral response presents a new simple but effective method. The application of a detector-based method allows a significant reduction of the uncertainty in the internal calibration of the photometric instruments, granting the continuity of the Photometric Laboratory operation contemporarily.

Spettroscopia di riflettanza risolta in tempo al Politecnico di Milano

A. Giusto C. D'Andrea, L. Spinelli, D. Contini, A. Torricelli, F. Martelli, G. Zaccanti, R. Cubeddu (Dip. Fisica, Politecnico di Milano - E-mail: cubeddu@fisi.polimi.it): Monitoring Absorption Changes in a Layered Diffusive Medium by White-Light Time-Resolved Reflectance Spectroscopy. IEEE Trans. Instrum. Meas. 59 (7), 1925-1932, 2010.
Diffuse spectroscopy of turbid media has assumed a crucial role in the characterization of biological tissues. In particular, broadband time-resolved optical spectroscopy allows the direct determination in a single measurement of both the optical parameters of the tissue and the concentration of its main constituents. Moreover, the possibility of performing parallel wavelength measurements allows the recording of data in real time, providing a system that is able to perform dynamic measurements. We used a white-light time-resolved spectroscopy system to monitor absorption changes in a layered diffusive medium. Measurements were performed in reflectance geometry, with a 2-cm source–detector distance, on a two-layer liquid phantom with optical properties similar to those of human tissues. By varying the concentrations of three inks with different spectral features, we changed the absorption coefficient of the layers to mimic functional brain activation and the systemic response in the scalp. Data were analyzed by a time-resolved spectrally constrained fitting method based on a homogeneous model of photon diffusion. Although this approach is based on a homogeneous model and employs a single source–detector distance, the technique is able to monitor changes in the lower layer, while it is scarcely affected by variations in the upper layer. These results were confirmed by numerical simulations based on a perturbation approach to diffusion theory. Preliminary in vivo measurements have been performed on healthy volunteers to monitor oxy- and deoxy-hemoglobin changes in the brain during a motor task. Although the overall sensitivity of the technique is reduced, in vivo results are in general agreement with the findings of the dedicated system for functional brain activity.

Interfaccia di lettura innovative per sensori dall’Università di Brescia

A. Depari, A. Flammini, D. Marioli, E. Sisinni, A. De Marcellis, G. Ferri, V. Stornelli (Dip. Elettronica per l'Automazione, Univ. di Brescia - E-mail: alessandro.depari@ing.unibs.it): A New and Fast-Readout Interface for Resistive Chemical Sensors. IEEE Trans. Instrum. Meas. 59 (5), 1276 – 1283, 2010.
The main issue concerning metal oxide (MOX) gas sensors is mostly related to the wide range of resistive values that the sensors can show. In addition, some sensors could have baseline resistive values up to tens of gigohms. To avoid the use of expensive picoammeters or the use of circuits adopting scaling factors, different solutions have recently been proposed, exploiting the resistance-to-time conversion (RTC) technique. They show good linearity and are suitable for the integration in a chip together with the elaboration unit, but they may require long measurement time (tens of seconds) if high resistance values need to be estimated. In addition, they may suffer the influence of a sensor parasitic capacitance, in parallel with the resistive component. In this paper, a new method is proposed to reduce the measuring time, keeping the advantages offered by the RTC approach and including a parasitic capacitance estimation feature. Particularly, an effective architecture, based on moving thresholds, has been proposed, simulated, and experimentally tested with commercial resistors (values between 1 MΩ and 100 GΩ) and capacitors (values between 1 and 47 pF). Finally, a fast sensor transient, due to a rapid change in the heating power, has been acquired with the proposed instrument and compared with a similar transient analyzed with a classical RTC approach. This test has shown the applicability of the interface for solutions requiring detailed information of the sensor response, such as the characterization of new sensors (e.g., nanowires) or the behavior analysis during nonstandard thermal profiles.

Misuratore di flusso a basso costo per pompe a circolazione extracorporea

M. Norgia, A. Pesatori, L. Rovati (Dip. Elettronica per l'Automazione, Univ. di Brescia) : Low-Cost Optical Flowmeter With Analog Front-End Electronics for Blood Extracorporeal Circulators. IEEE Trans. Instrum. Meas. 59 (5), 1233 – 1239, 2010. The design and realization of a new low-cost instrument for real-time measurement of blood flow particularly developed for extracorporeal blood circulator systems are presented. A self-mixing interferometric technique combined with a dedicated analog signal processing system was adopted to perform an accurate flow measurement. The developed system exhibits an accuracy lower than 3%. The cost of the entire measuring system has been estimated to be about 50 euros.

SENSORI E RETI DI SENSORI

MEMS ibridi per misure di temperatura dall’Università di Brescia

D. Marioli, E. Sardini, M. Serpelloni (Dip. Elettronica per l'Automazione, Univ. di Brescia - E-mail: daniele.marioli@ing.unibs.it): Passive Hybrid MEMS for High-Temperature Telemetric Measurements. IEEE Trans. Instrum. Meas. 59 (5), 1353 – 1361, 2010.
A contactless sensor represents an attractive solution for high-temperature measurements in harsh environments, where the use of cables is not suitable, and where the temperature values are beyond those permitted by active electronic circuits. Temperature sensors have a wide variety of applications in automated processes for temperature control and regulation. This paper describes a passive sensing device suitable for high-temperature measurements consisting of a microfabricated temperature-sensitive variable capacitor and a planar inductor designed for high-temperature environments. Another readout inductor constitutes, together with the planar inductor, a telemetric system, which is a coupled transformer with the readout connected to the measurement electronics. The proposed passive hybrid microelectromechanical systems (MEMS) consists of an interdigitated capacitor bonded to the planar inductor. The hybrid sensor behaves as an LC resonant circuit in which the interdigitated capacitor represents the capacitance and the planar inductor is the inductance. The temperature induces a displacement of the conductive electrodes of the interdigitated capacitor toward the fixed electrodes realizing a temperature-sensitive variable capacitor. An equivalent circuit scheme of the variable capacitor and the planar inductor has been analyzed. Two telemetric measurement methods, relying on a frequency variation output, have been tested. The whole system has been tested in the laboratory, and several results are reported. Finally, the sensor prototype was fabricated and successfully characterized up to 330 °C as a proof of concept of temperature sensing through passive wireless communication. The proposed telemetric temperature system can be a solution for efficiency monitoring and predictive maintenance for harsh and complex environments, thereby eliminating the need for physical contacts, active elements, or power supplies, which cannot withstand harsh environments.

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