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The restrictions associated with the current SARS-Cov-2 pandemic are having a major impact on nearly all human activities and interactions; among these, the didactic and education field certainly has a prominent place. In the case of either complete lockdown or reduced accessibility to facilities and classrooms, the participation of students was severely limited for safety reasons. In particular, laboratory activities, already compromised by a large number of students of some classes, suffered from the restrictions, thus making it difficult to guarantee the possibility of live operating on instruments for the execution of measurements of different quantities of interest. To overcome the considered problem, this article proposes the use of enabling technologies of the Internet of Things and the fourth industrial revolution to allow students to achieve correct and complete training in laboratory activities. To this aim, remotely controlled instruments are used and displayed in augmented reality on consumer devices, such as mobile phones, tablets, or personal computers. The continuous availability of access to the instruments along with the realism in their representation and use ensures a positive and effective involvement of the students.

Designing and implementing a remote laboratory has long been a professional job, carried out by experts working in synergy with teachers. Nowadays, thanks to the availability of advanced tools, the implementation can be assigned as a student project related to advanced measurement and automation classes. The development of the project happens to have an important educational validity, since it allows the student to get familiar with principles and technologies that characterize intelligent manufacturing and smart environments, as central elements of Industry 4.0. In particular, the student has the opportunity to increase knowledge of Internet technologies that more and more often are substituting for the proprietary solutions, previously adopted in the industry for process monitoring and automation.

Carrying out experiments to understand the nature of the physical phenomenon turns out to be a fundamental step in the field of physics education, especially when lab activities characterized by possible personal risk for students are taken into account. In these cases, assuring a safe environment for students is mandatory. In this paper, the authors aim to make students relive a laboratory experience of gamma radiation spectrum measurement thanks to an Augmented Reality (AR) application capable of rendering an actual remote experiment on the students' mobile. This goal was achieved using an Internet of Things (IoT) paradigm protocol, such as the Message Queue Telemetry Transport (MQTT), and an STM32L152RE microcontroller by STMicroelectronics to control stepper motors for gamma ray detector movement with respect to the source. To make the experience as realistic as possible, AR is used to view reproductions of sources under test and detectors through proper target recognition. In particular, displacement and rotation of a fake detector are sent to the actual apparatuses in a safe laboratory and applied to the actual detector that measure the gamma ray spectrum of known radioactive sources. It is worth noting that the proposed approach is not limited to application aimed at teaching, but has the potential to interface with industrial applications, with a view to Industry 4.0, as an optimization of production processes through the remote management of resources, to perform advanced analysis, to have a control over the state of machines and industrial production times.

The paper deals with an analytical method for solving the problem of optimal positioning of IEDs used as circuit breakers for isolating the fault in medium voltage grids. The use of IEDs allows to automatically select the faulty section by means of a logic selectivity approach on medium voltage grids with radial topology. The optimization of their position assures the maximum benefits granted by the set number of IEDs installed. Two different approaches to solve the problem are presented. The first one solves the problem through an exhaustive analysis of all possible scenarios. The second one exploits integer linear programming with the branch and bound technique. The latter, being an exact resolution technique, will provide, like the first approach, the exact solution to the problem, with notable advantages in terms of computational effort.

A framework for simulating wide area measurement system (WAMS) of electrical transmission networks to test measurement algorithms is proposed in the paper. The framework has been implemented by a joint team involving the Italian transmission system operator (TSO), Terna S.p.A, and the University of Naples Federico II, and is essential to assess the performance of algorithms estimating network variables before making them operational on the real WAMS. On the other hand, the algorithm performance must be evaluated on a system that reproduces as faithfully as possible the problems characterizing an actual monitoring system. The authors propose a mixed solution including open-source software for managing timestamped data streams and Matlab script for both emulating PMUs and measurement algorithm. In the paper also preliminary tests carried out in order to assess the framework reliability are described.

The paper deals with the analysis of inter-area oscillations. that originates from power transients occurred in high extension grids. The research activity is focused on the implementation of a method capable to provide the manager of the national transmission grid with a tool for real time and accurate monitoring of the power system stability. In particular, the authors present a signal-based algorithm which, starting from the values estimated by the Phasor Measurement Units (PMUs) on the grid, allows the online monitor of the parameters (damping and frequency) characterizing the inter-area oscillations. The proposed algorithm is based on the Particles Swarm Optimization (PSO) method, but the traditional PSO has been enhanced through the use of a Continuous Weighted Average (CWA) which, at each iteration step, filters the PSO outputs assuring the reliability of the estimates.

Radiological threat (i.e., the risk associated with radioactive isotopes) is usually associated with military and civil applications involving either radioactive weapons or other radiological dispersal devices (e.g., deposits in soil or water, nuclear plants and so on) [1]. In recent years, some authors evidenced that limited quantities of radioactive materials can cause heavy damages and losses if they are ingested or inhaled [2], thus providing criminal terrorists with alternative strategies for their attacks based on radioactive water sprays, as an example.

Experimental practice in laboratory is a fundamental teaching issue in electrical and electronic measurement courses. Unfortunately, crowded classes, along with limited universities resources, do not allow to meet this need through actual laboratory sessions. In such a context, remote laboratories have proved to be an excellent solution. A significant added value, in a remote laboratory, is the possibility to modify the test circuit, in order to vary the type of experiment. The authors suggest, in the paper, to overcome t he considered limitations by integrating inside the remote laboratory suitable devices that can be remotely configured, i.e. a Field Programmable Analog Array (FPAA). FPAA is exploited for emulating the behavior of a large variety of analog circuits, thus making it possible for users, either students or technicians, to select the desired test circuit and carry out the experiment from home.

The performance parameters defined in the IEEE Standard 1057–2007 do not specify the standard uncertainty of the reconstruction levels of digitizing waveform recorders. Not knowing the standard uncertainty of the reconstruction levels affects, in turn, the evaluation of the uncertainty of a number of measurement approaches, based on digital signal processing techniques, which utilize the data collected by a digitizing waveform recorder as the input data. A method to evaluate the uncertainty of memoryless waveform recorders embedded in off-the-shelf digitizing oscilloscopes is proposed here. The method is based on an experimental approach that can be carried out anytime the input signal is repetitive, the frequency response of the oscilloscope can be considered flat, and the dynamical effects are negligible. To qualify the proposed method, the uncertainty estimation obtained by applying it in several experiments is compared with that gained by means of a B-type evaluation.

Distributed control strategyrepresents the most promising solution to enhance the lackluster energetic performance of mismatched PhotoVoltaic (PV) systems. Moreover, many factors that contribute to such poor performance are still to be explored. To fully understand the advantages offered by the Distributed Maximum Power Point Tracking (DMPPT) approach, the implementation of a DMPPT emulator is necessary. Based on the above needs, this paper describes the realization and use of a Buck based DMPPT emulator and shows its high flexibility and potential. The realized device is capable to emulate the output current vs. voltage (I-V) characteristics of many commercial PV modules with a dedicated Buck DC/DC converter not only in controlled atmospheric conditions but also with different currents rating of the switching devices. The system implementation is based on a commercial power supply controlled by a low-cost Arduino board. Data acquisition is performed through a low-cost current and voltage sensor by using a multichannel board by National Instruments. Experimental results confirm the validity and potential of the proposed DMPPT emulator.

In the paper, an analytical method for determining the optimal positioning of intelligent electronic devices in medium voltage grids is proposed. Intelligent electronic devices are automated devices able to communicate one with each other and command the circuit breaker in order to localize and isolate a line fault as fast as possible. However, the number of intelligent electronic devices to install has to be limited, due to the relevant installation costs and the reduction in the transmission bandwidth caused by the increased number of exchanged messages. So, the electrical distributor has to carefully detect the nodes of the grid where the intelligent electronic devices have to be installed. The authors propose a method based on integer linear programming, which, given the number of intelligent electronic devices to install, finds their optimal position, i.e., the one that minimizes the penalties associated with the power down experienced by customers. In order to highlight the offered advantages in terms of computational effort, the proposed approach has been assessed with a real medium voltage grid.

Virtual instruments let the user define custom measurement approaches to cope with specific goals. The use of virtual instruments also raises an important issue, which concerns the evaluation of the uncertainty of the measurement results. To face this issue, a change in the praxis currently adopted to interpret the analog-to-digital converter (ADC) datasheets released by the manufacturers for documenting their products seems necessary. This change should be the consequence of modifications and/or integrations of the standard documents adopted by the same manufactures, by the way proposed by the scientific community. Modifications and/or integrations should assure the compliance between parameters and methods for ADC testing and recommendations contained in the guide to the expression of uncertainty in measurement.

In the paper a remote laboratory as educational tool in measurement and automation courses is presented. Industry 4.0 and IoT paradigms require future information engineers to be able to use enabling technologies not only for the automation of measurements, but also for their remote management. For this purpose, a solution is proposed that makes the students an active part in the process of realization of the remote laboratory. An architecture involving typical laboratory instruments, introduced during measurement courses, and a server to allow remote access to laboratory equipment is implemented. The realization of the software architecture, however, is left to the students who, under teacher's guide, learn how to use the tools and programming environments to build up remote measurement stations.

The paper presents an innovative system for the simultaneous noninvasive monitoring and synchronized storage of the photoplethysmographic (PPG) signals and blood pressure (BP) values. Because it is noninvasive, the proposed monitoring system will permit to achieve signals from both healthy and un-healthy patients and then to create a wide and heterogeneous base of knowledge to properly train automatic classifiers. The final aim is to permit the reliable BP evaluation through the umpteen IoT devices able to acquire the PPG signal, nowadays available on the market. This will permit the BP monitoring every time and every were and then the early diagnosis of several cardiovascular diseases.

The paper deals with the distributed monitoring of harmonic and interharmonic pollution in electrical power delivery systems. In order to measure the disturbances and to identify the sources in a wide grid, a distributed measurement system with hundreds of measurement nodes has to be adopted. With the aim of obtaining the reduction of realization costs, the authors propose an innovative distributed architecture, based on cost-effective nodes, that takes advantage from the compressive sampling strategy. Differently from traditional approach, the network nodes will be only mandated to acquire and to digitize the line voltage directly in a compressed form, whereas a central measurement unit will receive data from all nodes deployed in the grid and will perform the successive signal reconstruction, making possible the use of low-performance hardware to realize them. The assessment of the compliance of the proposed measurement technique with the current power quality standards turns out to be mandatory, thus verifying the absence of artifacts introduced by the adopted compressed sampling approach. © 2015 Elsevier Ltd. All rights reserved.

The paper aims at experimentally assessing the metrological performance of a compressive sampling (CS)-based terahertz (THz) imaging system, an emerging technology for carrying out non-destructive tests of materials in order to detect defects and flaws. Differently from systems based on traditional raster scan, the exploitation of CS allows, in fact, obtaining images of interest in a reduced observation interval to the detriment of accuracy. In literature, several studies have faced the topic at hand showing results obtained in simulated and real conditions. On the same way, the authors have decided to focus their attention on the experimental investigation of the impact of some uncertainty sources on the final image reconstruction realizing a metrological characterization that could be used in different fields as for example aerospace. It is so possible to provide a preliminary roadmap capable of driving experimenters in the definition of the main features of the measurement setup to achieve a defined goal in term of reconstruction quality.

The problems related to the use of a split-coil permeameter for measuring the magnetic properties of materials with low relative permeability are faced. In particular, a challenging problem arises from the series production of steel tapes: magnetic and paramagnetic materials, in fact, exhibit different magnetic properties according to the production process (i.e. annealing and cold work). Consequently, samples of this material differently treated have to be characterized in order to find the optimal cold work and annealing able to minimize raising of magnetism. In this paper, fluxmetric methods, widely employed for magnets testing, are extended to the characterization of feebly magnetic materials. A case study for the series production of steel tapes about co-wound 1.430 stainless steel tapes, the material used for the quench detection in ITER TF coils [1], is presented.

LPWAN systems are being deployed in lightly licensed regional bands. For applications with low data rate and low duty cycle, LPWAN extends battery life, reduces cost and offers improved link budgets compared with current cellular formats. Networks often use a star topology around a gateway node. LoRa is a Sub-GHz wireless technology designed for low power, unlicensed, Long Range operations. The communication performance of this technology was assessed. The results indicated that this technology can provide very robust communication even in the presence of high noise level.

Over the past few years, the scientific community, both in academia and industry, witnessed a continuous and persistent effort in order to close the unexplored portion of the electromagnetic spectrum called THz gap, ranging from 100 GHz to 10 THz. Thanks to its properties, the THz technology finds application in diverse dual-use areas, spanning from chemical to pharmaceutical, biology and environmental sciences, and everyday applications within a broad range of industries including security, cultural heritage, manufacturing, and aerospace sectors. After a brief description of the common architecture of THz system, we focus here on Time Domain Spectroscopy (TDS-THz) THz system, we provide here some examples of dual-use THz applications, such as spectroscopic measurements of unknown objects or contactless and non-destructive analysis of different materials by spatial imaging operations.

The terahertz (THz) frequency region is often defined as the last unexplored area of the electromagnetic spectrum. Over the past few years, the full access has been the objective of intense research efforts. Progress in this area has played an important role in opening up the possibility of using THz electromagnetic radiation (T-waves) in science and in real-world applications. T-waves are not perceptible by the human eye, are not ionizing, and have the ability to cross many non-conducting materials such as paper, fabrics, wood, plastic, and organic tissues. Moreover, the use of THz radiation allows non-destructive analysis of the materials under investigation both by study of their "fingerprint" via spectroscopic measurements and by high-resolution spatial imaging operations, exploiting the see-through capability of T-waves. Such technology can be applied in diverse areas, spanning from biology to chemical, pharmaceutical, environmental sciences, etc. In this chapter, we will present the typical architecture of measurement systems based on the THz technology, detailing what are the parameters that define their performance, the measurement methods, and the related errors and uncertainty, and focusing at the end on the use of time-domain spectroscopy for the evaluation of different material properties in this specific frequency region.

The dynamic characterization of digital to analog converters (DACs) is still an open issue, on whose criticality both the scientific and industrial community agree. At present, only a draft standard (IEEE P1658) has been proposed, which is currently being discussed. In the last years, in fact, several works have been presented in the literature, but at the moment none of them seems to be robust enough to be easily included in the standard. Most of the proposed method, which are well structured from a theoretical point of view, and yield very encouraging simulative results, seem to suffer from some problems in the practical implementation. Such problems basically depend on the accuracy of the instrumentation they need to be implemented. The paper presents a contribution in this direction, consisting in a method for the dynamic characterization of DAC that is capable of reconstructing and analyzing DAC output with an equivalent resolution much greater than that of DAC itself even though a low resolution data acquisition system is used. The method consists of four phases each of which is carefully described and discussed in the following: (i) generation of DAC output signal, (ii) signal conditioning by means of an analog filter and a differential amplifier, (iii) acquisition and reconstruction of signal generated by the DAC, and (iv) recognition of the codes associated with the generic acquired voltage value. The method is also implemented in a suitable measurement station through which several tests have been performed on actual DACs. The experimental results show the good performance of the proposed method, which can thus be considered as a useful contribution to the draft standard IEEE P1658.

Digital-to-analog converters (DACs) are widely employed in control and automation, test and measurement, and communication systems. However, guidelines for the definition of static and dynamic features of DACs, as well as models capable of describing the different effects of the major nonidealities or drawbacks the DAC can suffer from, are still incomplete. This paper presents a new model capable of describing the functioning of a real DAC affected by horizontal quantization, clock modulation, vertical quantization and integral nonlinearity. The model permits evaluating the effects of the aforementioned nonidealities through straightforward formulas, which are characterized by a low computational burden. Results of experiments conducted on a real DAC to verify the reliability of the model are also shown.

Reducing or optimizing electrical power consumption is one of the most fundamental goals within the current frameworks of smart energy management. This approach would be spread from the industrial plants, characterized by high consumptions often well distributed throughout the day, down to the domestic utilities, typically discontinuous and with limited consumption at the single user level. More specifically, it is desirable for the latter case to be able to control in a simple and effective way the power consumption of typical household appliances by means of technologies that are already used and spread (such as tablets and smartphones) to become aware of their actual impact, both economic and environmental. To this aim, the authors present the proof-of-principle of user-friendly monitoring system for power consumption awareness based on the recent technologies of Internet of Things (IoT) and Augmented Reality (AR). In particular, common devices such as smartphones associated along with appropriate measurement nodes and a suitable app, developed to the purpose, allow consumers to view in AR environment electrical consumption of their domestic electrical loads to consciously decide whether to switch them off. Performance of both sensor nodes and AR environment were preliminarily assessed in either laboratory experiments or actual household context, highlighting the promising effectiveness of the proposed approach.

The Remote Didactic Laboratory Laboratorio Didattico Remoto - LA.DI.RE. ldquoG. Savastanordquo is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It involves about 20 Italian universities and provides students of electric and electronic measurement courses with access to remote measurement laboratories delivering different didactic activities related to measurement experiments. In order to demonstrate the versatility for didactic use, the overview of some experiments is given. The didactic experiments summarized in this paper concern measurement characterization of instruments and communication systems, measurement devices for remote laboratories, basic electrical measurements, magnetic measurements, electromagnetic-interference measurements, and signal processing for measurement applications.

The paper deals with the problem of improving the maximum sample rate of analog-to-digital converters (ADCs) included in low cost wireless sensing nodes. To this aim, the authors propose an efficient acquisition strategy based on the combined use of high-resolution time-basis and compressive sampling. In particular, the high-resolution time-basis is adopted to provide a proper sequence of random sampling instants, and a suitable software procedure, based on compressive sampling approach, is exploited to reconstruct the signal of interest from the acquired samples. Thanks to the proposed strategy, the effective sample rate of the reconstructed signal can be as high as the frequency of the considered time-basis, thus significantly improving the inherent ADC sample rate. Several tests are carried out in simulated and real conditions to assess the performance of the proposed acquisition strategy in terms of reconstruction error. In particular, the results obtained in experimental tests with ADC included in actual 8- and 32-bits microcontrollers highlight the possibility of achieving effective sample rate up to 50 times higher than that of the original ADC sample rate.

Nowadays, a variety of measurement applications require the acquisition and processing of signals coming from many disseminated sensors. To reduce the cost of the overall measurement process, the above-mentioned tasks are typically performed by devices like microcontrollers, low cost data acquisition systems (DASs), field gate programmable arrays (FPGAs), and so on. This is particularly true when smart-sensors or wireless sensor networks are considered. These devices are characterized by some limitations mainly concerning with the reduced internal memory and the use of multiplexing circuits to share the same analog to digital converter (ADC) over different physical channels. The former limitation affects the maximum observation time the devices are able to cover with a single shot acquisition, the latter imposes unwanted phase shifting on the acquired signals. The use of modern acquisition and processing techniques could be of some help. One of the most promising is the compressive sampling (CS), which can assure good signal reconstruction starting from very few acquired samples. To this aim, the paper deals with the definition, implementation and experimental characterization of a CS-based acquisition approach specifically addressed to cost-effective multi-channel DASs, like those characterizing typical 8 or 32-bit microcontrollers. In particular, the paper aims at showing the reliable phase reconstruction capability also in the presence of multiplexed multichannel architectures. A number of tests conducted both on numerical and actual experiments are carried out to assess the performance of the proposed approach. In particular, the results obtained on real data acquired by means of the considered low-cost platforms shows the efficacy of the adopted approach; phase shift as low as few milliradians are, in fact, experienced.

The paper deals with the problem of simultaneously enhancing both horizontal and vertical resolution of analog-to-digital converters, with specific regard to low-cost conversion systems. To this aim, the authors propose the combined exploitation of a suitable Compressive Sampling (CS) approach and a proper digital signal processing stage. In particular, starting from a reduced number of digitized samples, the proposed CS-based sampling approach allows to recover an oversampled version of the input signal, whose spectral content is properly shaped to reject the most of in-band noise. The successive processing stage, implementing a low-pass filter, is mandated to drastically attenuate out-of-band noise components. Tests carried out on an actual microcontroller (namely, PIC32MX360L512 by Microchip) evidence the promising performance of the proposed sampling strategy. Results obtained either on single tone or multisine signals highlight a gain up to 3.5 bits in vertical resolution, while the sample rate increases 50 times with respect to the actual one adopted to randomly sample the input signal of interest. © 2014 Elsevier Ltd. All rights reserved.

Modeling and analysis of the functioning of power systems is very difficult because of time varying and non-linear behaviors. Often power systems are described trough simplified approaches. The most widespread one recognizes load conditions that can be considered stationary within limited time intervals, in order to apply thus standard harmonic analysis techniques. Here a data segmentation approach to distinguish the time intervals in which stationary load conditions can be recognized is discussed and assessed.

The deeper interconnection and the increasing presence of active devices on the electrical networks is raising many issues concerning with the monitoring of Power Quality phenomena. Voltage parameters related to the supply of electricity and current parameters related to the working of electrical apparatuses have to be monitored as accurately as possible. To this aim specific international standards impose strict measurement methods and complex measurement instrument architectures, usually based on the computation of real time Fast Fourier Transforms, to be adopted for the purpose. In particular, considering poly-phase systems, four currents and four voltages have to be detected, synchronized, measured and analyzed with good accuracy and spectral resolution. This imposes to the measurement the calculation of eight FFTs in a very short time. These requirements conflicts with the need of cost-effective measurement instruments required by spread and distributed monitoring systems in many points of the electrical plant. To face this issues this paper proposes the study and the tuning of compressive sampling (CS) techniques capable of assuring reliable reconstruction of the signal of interest from very low acquired samples. In particular, to make the CS use more feasible, the authors have also exploited some peculiarities of the CS approach in order to reduce the computational burden usually associated with the mere application of its acquisition and reconstruction protocol. Preliminary results confirm the applicability of the proposed solution.

The paper deals with the realization of low-cost hand prosthesis for amputee people living in developing countries. In particular, the problems associated with the implementation of acquisition, processing and actuation blocks capable of assuring suitable performance in terms of reliability with a reduced budget have been faced and solved. To this aim, a specific architecture, based on a microcontroller PIC18F23K22 by Microchip®, is implemented and described. Particular attention is paid on the conditioning block adopted, due to the very low amplitude signals associated with myoelectric phenomena. To this aim, a suitable calibration procedure is proposed to overcome the problems associated with the dependence of myoelectric signals with the specific amputee person.

Tests of field programmable analog arrays (FPAA) are required to assess tolerance to variations of components, due to aging, uncertainty, or external disturbances. The paper focuses on radiated electromagnetic energy as a cause for a possible faulty behavior: results show that input and output channels of the FPAA are affected by the presence of noise due to the coupling of the incident field with the board, and that the susceptibility profile depends on the configuration of the FPAA and the field’s polarization. Therefore, topology and electromagnetic characteristics of the board must be carefully designed. Moreover, the transfer function is susceptible to the incident field to a degree that depends on the configuration of the FPAA and the field’s amplitude and frequency. This limits application of FPAAs in critical applications like in the automotive and aerospace industry, where fields with large amplitudes are likely to be encountered during normal operation.

The paper deals with a low cost measurement station for DAC dynamic characterization. The characterization method is based on the estimate of the DAC output voltage through the measurement of time intervals. These are performed by the DSP, which evaluates the time between two edges of the input signal. A proper system has been implemented with the aim of conditioning the DAC output signal in order to obtain a resulting square shaped signal with width proportional to the DAC output voltage. The advantages of the method are: (i) DAC voltages estimated by means of time interval measurements, this permits to obtain higher resolution respect to amplitude measurements; (ii) measurement set up characterized by limited size and costs, this supports the realize of BIST (built-in self-test) system.

A fair automatic test equipment in which the control operations can be performed by remote units is presented. The proposed solution is based on web services and provides the user with a simple interface for connecting to remote resources. Moreover, it implements an original ultra-light communication protocol. The proposed solution can be attractive both from an industrial and a didactical point of view.

Functional tests of field programmable analog arrays (FPAA) are required to assess tolerance to uncontrolled and unintentional variations in the components characteristic parameters, like for example a change in the values of capacitances and gains of the differential amplifiers which may be due to aging, uncertainty (i.e., a difference between the actual and nominal values), or to an outer disturbance like radiated electromagnetic energy. The paper focuses on the latter as a cause for a possible faulty behavior: experimental results have shown that the expected performances are distorted by the presence of noise added to the useful signals due to the coupling of the external electromagnetic field with the circuitry. The results indicate that the susceptibility features depend only marginally on the specific configuration given to the FPAA, leading to the conclusion that the topology and electromagnetic characteristics of the board on which the device is mounted must be carefully designed.

Assessing the dynamic performance of digital-to-analog converters (DAC) is challenging due to the limited resolution of flash analog-to-digital converters (ADC) that are used for the scope. Current solutions are either difficult to be implemented in practice or suffer from serious limitations due to the uncertainty of the hardware utilized. The paper present an innovative method for testing the dynamic performance of a DAC that uses a low resolution ADC just as the other solutions, but exploits it to digitize an amplified version of the error signal, instead of the DAC output signal. The limitations due to the hardware are thus overcome. The results of a number of simulations confirm the feasibility of the proposed method.

In this paper, a novel method for the compensation of commercial current transformers (CTs), based on the insertion of a series analog circuit at the secondary winding is proposed. The method allows the enhancement of existing transformers which can, thus, reach the 0.2 ratio error and a phase error lower than the measurement sensitivity, only by means of the insertion of a low-cost circuit. The feasibility of the method has been preliminarily verified by applying the model of the compensating circuit to the actual signal acquired at the transformer terminals. Successively, the circuit has been realized and applied to a commercial CT. Experimental tests, aiming at assessing the compensation performance, have been conducted by varying the magneto-motive force at both industrial and higher frequencies.

In the paper a low cost method for the compensation of Voltage Transformers (VTs) is proposed. The compensation technique is based on a proper circuit connected to the secondary terminals that, by sensing the VT primary current, generates a voltage that compensates the primary voltage drops. The designed circuit for the compensation is physically separated from the VT, so that it proves to be easily employed for enhancing the performance of commercial VT or VT already working on the transmission network. For the measurement of VT primary current, a proper transducer has been designed; it allows the measurement of low current (in the range of milliampere) granting the required insulation between the primary circuit and the measurement section. In order to configure the compensating circuit, the VT primary parameters have to be known; a suitable method, thus, for the characterization of VT, is also proposed.

A typical approach for the compensation of voltage transformers (VTs) is based on the generation of an auxiliary voltage that has to be added to the secondary electromotive force. The auxiliary voltage has to compensate the voltage drops due to the current flowing in the primary circuit. At this aim, the compensating circuit has to sense the primary current in the different working conditions. It is clear that the accuracy of the employed current transducer affects the compensation effectiveness, since it modifies the auxiliary voltage. In the paper an analysis of the sensitivity of the performances of VT compensation with respect to the variation of the current transducer accuracy is performed. The obtained results allow the selection of the proper current transducer that represents the suitable trade off between the transducer costs and the achievable accuracy class for the compensated VT.

This paper proposes the use of field programmable analog arrays (FPAAs) as adaptive conditioning blocks for ultrasonic sensors. The uncertainty achievable through this technique, in fact, results very sensitive to the measurement conditions, due to the attenuation affecting the echo during its propagation. Indeed, FPAAs emulate analog circuits whose characteristics have to be dynamically tuned according to different operating conditions. Actually, the signal provided by the ultrasonic sensor is properly processed in order to improve the overall measurement accuracy. In this paper, the prototype of a distance meter based on time-of-flight (TOF) measurement is presented in order to evidence the advantages gained by FPAA features in processing the sensor output to compensate echo attenuation and distortion versus target distance. The prototype working is supervised by a digital signal controller (DSC) whose tasks are: 1) driving the ultrasonic transducer; 2) performing the echo acquisition; 3) tuning on the fly the FPAA features; 4) evaluating the TOF; 5) measuring the target distance; and 6) delivering the final result to the end user. This paper is completed by the results achieved in a number of experimental tests allowing interesting considerations to be drawn. In particular, the experiments confirm the prototype reliability and effectiveness also with ultrasonic echoes characterized by very low signal-to-noise ratios.

The Remote Didactic Laboratory Laboratorio Didattico Remoto -LA.DI.RE. “G. Savastano” is an e-learning measurement laboratory supported by the Italian Ministry of Education and University. It provides the students of electric and electronic measurement courses with access to remote measurement laboratories, delivering different didactic activities related to measurement experiments. The core of the software architecture is the integration of the Learning Management System (LMS) with the remotely accessible measurement laboratories through web services and thin client paradigm, providing a new approach to remote experiments on measurement instrumentation. The overview of this paper is on the different solutions concerning the thin client technology, and the solution implemented is described. This solution takes into account the delivered services to students and teachers and permits optimization of the communication performances. The results of the comparison among the performances of different implementations of the thin client paradigm highlight the advantages of the adopted solution. As a consequence, the description of the thin client protocol implemented, together with the presentation of the LMS and delivered services given in a previous paper, makes an exhaustive analysis of the software architecture of the LA.DI.RE. “G. Savastano.”

In this paper the authors propose an intelligent and stand-alone measurement instrument for environmental monitoring and control applications. By an embedded computational intelligence technique, the instrument can acquire and test data according to available information. The projected system consists in a Smart Web-Sensor sensing the electromagnetic field exposure levels. The sensor equipment includes an isotropic magnetic field transducer, a GPRS modem, a DSP platform and an interface display. In details, the realized measurement system is able to process acquired signals by performing mathematical algorithms in order to verify the conformity with the law exposure limits and to characterize possible alarm occurrences. The data processing stage is qualified by a further power-spectrum analysis, that allows to get information in the frequency domain on the electromagnetic field spectral components. Information regarding the operating status of sensor is stored in an internal embedded memory, so keeping trace on its metrological characterization. In this way the built-in knowledge on the integrity of acquired data is used to guarantee the reliability of the computational process.

For last years, a large number of universities, have been focusing their attention on the opportunity of making students capable to observe experimental activities, from their home and at any time, through Internet. The realization of remote laboratories for engineering disciplines, in particular for a measurement course, presents further problems, since it is required that students interact with remote circuit and handle measurement instruments. The crucial task is, hence, to implement Web/Internet-enabled applications that can be fully controlled and monitored from remote locations. There is a wide variety of solutions enabling the remote control of measurement instrumentation; each one is characterized by its peculiarities, advantages, and drawbacks. In the paper an overview on the most adopted technologies is performed. Particular attention is paid on Web Services technology that proves to be a general solution, suitable for each type of application.

The Remote Didactic Laboratory Laboratories Didattico Remoto - LA.DI.RE. "G. Savastano" is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It provides the students of electric and electronic measurement courses with the access to remote measurement laboratories delivering different didactic activities related to measurement experiments. The paper describes the innovative aspects concerning the software and hardware architecture, and the delivered services to both the teachers and students. The core of the delivered services is the integration of the learning measurement system with the remotely accessible measurement laboratories through the Web. Moreover, the advantages of the proposed software and hardware architecture are highlighted in comparison with the traditional architectures

The paper concerns with the realization of a device for measurement of EM conducted interferences, in alternative to set-up suggested by CISPR Standard rules. This technique allows, in particular, the separation of common mode and differential mode interference components. On the contrary of traditional set-up based on ?-?- type LISN, the proposed system is less expensive and more compact. The device is based on three current and voltage probes with wide frequency bandwidth and three hybrid junctions separating the disturbance components; a dsPic is mandated to alternatively select the proper output, sample the interference signal and transmit data to an external process unit.

In the paper the authors propose the improvement of three new power quality indexes presented in a previous work (De Capua, 2004) for exhaustively detecting voltage sags. In fact, during the indices' experimental assessment, some weak points of the previous presented indices have arisen. After indices' correction, ANOVA analysis have been performed, in order to investigate indices' sensibility with regards to sag depth and duration. At this aim a full experimental analysis has been conducted by applying a multilevel multivariable experiment. Through ANOVA analysis, moreover, a cost function has been realized to correlate the indexes values to the effective cost of lost quality for users who need the absolute absence of sag occurrence. Subsequently the indices' uncertainty has been estimated; a random-fuzzy technique has been preferred, since the ISO guide shows its limits in presence of DSP-based algorithms

The Remote Didactic Laboratory Laboratorio Didattico Remoto ? LA.DI.RE. "G. Savastano" is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It involves about twenty Italian universities and provides the students of electric and electronic measurement courses with the access to remote measurement laboratories delivering different didactic activities related to measurement experiments. In order to demonstrate the versatility for didactic use, the overview of same experiments is given. The didactic experiments summarized in the paper concern with: measurement characterization of instruments and communication systems, measurement devices for remote laboratory, basic electrical measurements, magnetic measurements, electromagnetic interferences measurements, and signal processing for measurement applications.

Remote laboratories originate from the attractive opportunity of exploiting the advantages offered by Internet to controlling instrumentation and hence conduct measurement processes from any location at any time. This capability has been employed in educational areas, developing remote laboratories at Universities, in order to provide a large number of students with laboratory experiences avoiding the problems of low availability of instrumentation and technical personnel. There is a wide variety of solutions enabling a measurement station to be controlled through the web, each one with its peculiarities. In the paper it is presented a remote laboratory to support the experimental session of the course of Measurement for Diagnostics and Quality, based on Macromedia Flash pages and .Net Web Services, whose main characteristics are platform independence and ease of use.

In this paper a sensor data fusion procedure for electromagnetic field monitoring is proposed. Distributed sensing and remote processing are the basic features of the employed architecture. In fact, in order to obtain meaningful information about the temporal and spatial variations, which characterize the electromagnetic field levels, a distributed network of wireless and mobile smart-sensors has been designed. The monitored region is a wide urban area, partitioned in small local zones. Each mobile station has the task to explore a specific zone. The qualification of the sensor network is achieved by the possibility to configure dynamically the partitioning of investigated area according to the needs. The refresh time of monitoring map, the thickness of the grid, the choice of sampling points and their locations are consequence of an experiment design and function of several influence parameters. Acquired data are sent in a short time to a processing unit for performing the fusion procedure. A two-level decision approach has been employed. For each local zone, a first algorithm extracts a local decision concerning warning or alert situations. This step permits to reduce data amount and perform a preliminary data fusion starting from the reliability information on the single sensor. A second procedure realizes the final aggregation of data extracting a global decision and a 'picture' about the behaviour of electromagnetic field levels. Local decisions and correlated information are aggregated in order to obtain a meaningful and a higher-quality 'image' of monitored phenomenon according to desired performances.

In the paper an analytical model based on measurement indexes is developed to assure the property of reliability of a web server's network. The proposed approach, making use of a fault tolerant technique, allows data transmission optimization in dispatching process. Simulations, representative of different operative conditions of network, evaluated through the measurement indexes used, have been carried out. Experimental results have been achieved applying the proposed algorithm to a real system, consisting of a web servers system controlling measurement instrumentation to perform a wide variety of measurement experiments and deliver the results. © 2005 IEEE.

In this paper the authors describe the implementation of a smart sensor based on microcontroller for the extraction of new conceived power quality indexes. The work is carried on starting from the improvement of three indexes presented in a previous work (De Capua et al., 2004) for exhaustively detecting voltage sags. After an examination of the loads which could be more susceptible to the duration or to the depth of the sag, an ANOVA analysis has been conducted in order to evaluate the indexes' sensibility to these characteristics of the sag. Then a new measurement algorithm has been implemented, that is considered more rapid for detecting a sag occurrence. Finally a dsPic-based smart sensor has been realized, to monitor the voltage RMS value and extract the indexes values. These values are transmitted to software located on an external peripheral, through serial communication, for the successive data processing stage.