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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.

This article deals with the parameters’ measurement of interarea oscillations, which are low-frequency damped oscillations that affect the high-voltage transmission lines when an unbalance between the power demand and the generated power occurs. The authors propose a method that processes the samples provided by the phasor measurement unit (PMU) and performs the online estimation of the parameters that characterize the interarea oscillations. The method takes advantage of the speed of a heuristic algorithm, such as the particle swarm optimization (PSO), but performs an enhancement on the results to increase the reliability. The tests carried out for the method assessment prove that the proposed method is characterized by a fast response, high accuracy, and excellent reliability, regardless of the type of oscillation that is considered.

The recent increase on the Internet of Things and Industry 4.0 fields has led the research topics to investigate on the innovative technologies that could support these emerging topics in different area of applications. In particular, the current trends are to close the gap between the physical and digital worlds, thus originating the so-called Cyber-Physical System (CPS). A relevant feature of the CPS is the digital twin, i.e., a digital replica of a process/product with which user can interact to operate on the real world. In this paper, the authors propose an innovative approach exploiting an Augmented Reality solution as Digital Twin for the measurement instrument to obtain a tight connection between the measurements as physical world and the Internet of Things as digital applications. In fact, by means of the adoption of the 3D scanning strategy, Augmented Reality software and with the development of a suitable connection between the instrument and the digital world, a Cyber-Physical System has been realized as an IoT platform that collect and control the real measurement instrument and makes its available in Augmented Reality. An application example involving a digital storage oscilloscope is finally presented to highlight the efficacy of the proposed approach.

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.

The topics of virtual, mixed, and extended reality have now become key areas in various fields of scientific and industrial applications, and the interest in them is made tangible by the numerous papers available in the scientific literature. In this regard, the Special Issue “VR, AR, and 3-D User Interfaces for Measurement and Control” received a fair number of varied contributions that analyzed different aspects of the implementation of virtual, mixed, and extended reality systems and approaches in the real world. They range from investigating the requirements of new potential technologies to the prediction verification of the effectiveness and benefits of their use, the analysis of the difficulties of interaction with graphical interfaces to the possibility of performing complex and risky tasks (such as surgical operations) using mixed reality viewers. All contributions were of a high standard and mainly highlight that measurement and control applications based on the new models of interaction with reality are by now increasingly ready to leave laboratory spaces and become objects and features of common life. The significant benefits of this technology will radically change the way we live and interact with information and the reality around us, and it will surely be worthy of further exploration, maybe even in a new Special Issue of Future Internet.

Three-phase motors are commonly adopted in several industrial contexts and their failures can result in costly downtime causing undesired service outages; therefore, motor diagnostics is an issue that assumes great importance. To prevent their failures and face the considered service outages in a timely manner, a non-invasive method to identify electrical and mechanical faults in three-phase asynchronous electric motors is proposed in the paper. In particular, a measurement strategy along with a machine learning algorithm based on an artificial neural network is exploited to properly classify failures. In particular, digitized current samples of each motor phase are first processed by means of FFT and PSD in order to estimate the associated spectrum. Suitable features (in terms of frequency and amplitude of the spectral components) are then singled out to either train or feed a neural network acting as a classifier. The method is preliminarily validated on a set of 28 electric motors, and its performance is compared with common state-of-the-art machine learning techniques. The obtained results show that the proposed methodology is able to reach accuracy levels greater than 98% in identifying anomalous conditions of three-phase asynchronous motors.

A superconducting permeameter is proposed to characterize the magnetic properties of high-energy superconducting magnet yokes at their operating temperature and saturation level. The main problem of superconducting coils, an undesired quench, was faced by specific protection simulations, which has led to a self-protected system. The superconducting permeameter was used to perform the magnetic characterization of ARMCO Pure Iron, the material for the new High-Luminosity Large Hadron Collider (HL-LHC) superconducting magnet yokes, which was performed at the cryogenic temperature of 4.2 K and a saturation level of nearly 3 T. Two case studies based on the new HL-LHC superconducting quadrupole and dipole magnets highlight the impact of the magnetic properties of the yoke on the performance of the superconducting magnets, showing that the common assumption that heavily saturated steels with similar chemical composition behave precisely the same way has been proven wrong.

The Distributed Maximum Power Point Tracking (DMPPT) approach is a promising solution to improve the energetic performance of mismatched PhotoVoltaic (PV) systems. However, there are still several factors that can reduce DMPPT energy efficiency, including atmospheric conditions, the efficiency of the power stage, constraints imposed by the topology, the finite rating of silicon devices, and the nonoptimal value of string voltage. In order to fully explore the advantages offered by the above solution, the implementation of a Boost based DMPPT emulator is of primary concern, especially if it behaves as a controlled voltage or current source. The repeatability of experimental tests, the tighter control of climatic conditions, the closing of the gap between the physical dimensions of a PV array and the space available in a university lab, the simplicity with which new algorithms can be tested, and the low maintenance costs are just some of the benefits offered by an emulator. This paper describes the realization and use of a Boost based Distributed Maximum Power Point Tracking (DMPPT) emulator and shows its high flexibility and potential. The device is able to emulate the output current vs. voltage (I&ndash, V) characteristics of many commercial PhotoVoltaic (PV) modules with a dedicated Boost DC/DC converter. The flexibility is guaranteed by the ability to reproduce both I = f ( V ) and V = g ( I ) characteristics at different values of not only the irradiance levels but also the maximum allowed voltage across the switching devices. The system design is based on a commercial power supply controlled by a low-cost Arduino board by Arduino (Strambino, Torino, Italy). Data acquisition is performed through a low-cost current and voltage sensor by using a multichannel board by National Instruments. Experimental results confirm the capability of the proposed device to accurately emulate the output I&ndash, V characteristic of Boost based DMPPT systems obtained by varying the atmospheric conditions, the rating of silicon devices, and the electrical topology.

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.

The construction of the superconducting magnets for the High-Luminosity upgrade of the Large Hadron Collider accelerator at Conseil Europeen pour la Recherche Nucleaire has resulted in demands for 1800 tons of ferromagnetic laminations for the magnet iron yokes. The magnetic properties of the selected steel, ARMCO Pure Iron, have been measured, within annealing treatment sequences from 750 °C to 850 °C, at operation temperatures of 4-300 K. It is shown that annealing treatment improves the magnetic performance of the material if the material is kept at room temperature. However, this improvement disappears after cooling down the material to the operation conditions of 4 K. The dependence on the operation temperature was shown by testing the material at the cryogenic temperature of roughly 4 K, 77 K, and at room temperature. The magnetic performance of the material shown at room temperature has not been found at cryogenic temperatures. Nevertheless, the results obtained are still acceptable in comparison to the properties of the alternative materials. Tests performed before and after the application of a mechanical stress have also been studied to validate the production process.

In this paper, the importance of magnetic material measurements in the framework of the design of magnets for particle accelerator is discussed. In particular, five samples of different ferromagnetic materials are analyzed experimentally and compared with literature results. These materials have been (or will be) used for producing yokes for several normal-conductor magnets at CERN, such as REX-ISOLDE main dipole, ELENA dipole and quadrupole, and SESAME dipole. The comparison with literature shows several disagreements. The main one of them is analyzed in detail in a case study based on finite elements simulation of a quadrupole magnet installed in CERN. This analysis shows that a good knowledge of the yoke initial magnetization curve is important to guarantee a given level of magnet performance, especially concerning its field quality.

In high-brightness LINear ACcelerators (LINACs), electron bunch length can be measured indirectly by a radio frequency deflector (RFD). In this paper, the accuracy loss arising from non-negligible correlations between particle longitudinal positions and the transverse plane (in particular the vertical one) at RFD entrance is analytically assessed. Theoretical predictions are compared with simulation results, obtained by means of ELEctron Generation ANd Tracking (ELEGANT) code, in the case study of the gamma beam system (GBS) at the extreme light infrastructure—nuclear physics (ELI-NP). In particular, the relative error affecting the bunch length measurement, for bunches characterized by both energy chirp and fixed correlation coefficients between longitudinal particle positions and the vertical plane, is reported. Moreover, the relative error versus the correlation coefficients is shown for fixed RFD phase 0 rad and rad. The relationship between relative error and correlations factors can help the decision of using the bunch length measurement technique with one or two vertical spot size measurements in order to cancel the correlations contribution. In the case of the GBS electron LINAC, the misalignment of one of the quadrupoles before the RFD between −2 mm and 2 mm leads to a relative error less than 5%. The misalignment of the first C-band accelerating section between −2 mm and 2 mm could lead to a relative error up to 10%.

The paper deals with a novel method to measure inter-area oscillations, i.e., electromechanical oscillations involving groups of generators geographically distant from one another and ranging within the frequency interval from 0.1 Hz up to 1 Hz. The estimation of the parameters characterizing inter-area oscillations is a crucial objective in order to take the necessary actions to avoid the instability of the transmission electrical system. The proposed approach is a signal-based method, which uses samples of electrical signals acquired by the phasor measurement unit (PMU) and processes them to extract the individual oscillations and, for each of them, determine their characteristic parameters such as frequency and damping. The method is based on Hilbert transformations, but it is optimized through further algorithms aiming at (i) improving the ability to separate different oscillatory components, even at frequencies very close to each other, (ii) enhancing the accuracy associated with the damping estimates of each oscillation, and (iii) increasing the robustness to the noise affecting the acquired signal. Results obtained in the presence of signals involving the composition of two oscillations, whose damping and frequency have been varied, are presented. Tests were conducted with signals either synthesized in simulated experiment or generated and acquired with actual laboratory instrumentation.

Massimo Polisiero,1 Paolo Bifulco,1 Annalisa Liccardo,2 Mario Cesarelli,1 Maria Romano,1 Gaetano D Gargiulo,3 Alistair L McEwan,3 Massimo D'Apuzzo2 1Department of Biomedical, Electronics and Telecommunication Engineering, 2Department of Electrical Engineering, University Federico II of Naples, Naples, Italy; 3School of Electrical and Information Engineering, The University of Sydney, New South Wales, Australia Abstract: The study reported here explored the design and realization of a low-cost, electromyographically controlled hand prosthesis for amputees living in developing countries. The developed prosthesis is composed of a light aluminum structure with opposing fingers connected to a DC motor that imparts only the movement of grasp. Problems associated with surface electromyographic signal acquisition and processing, motor control, and evaluation of grasp force were addressed, with the goal of minimizing cost and ensuring easy assembly. Simple analog front ends amplify and condition the electromyographic signals registered from two antagonist muscles by surface electrodes. Analog signals are sampled at 1 kHz and processed by a microcontroller that drives the motor with a supply voltage proportional to the muscular contraction, performing the opening and closing of the opposing fingers. Reliable measurements of the level of muscle contractions were obtained by specific digital processing: real-time operators implementing the root mean square value, mean absolute value, standard deviation, and mean absolute differential value were compared in terms of efficiency to estimate the EMG envelope, computational load, and time delay. The mean absolute value operator was adopted at a time window of 64 milliseconds. A suitable calibration procedure was proposed to overcome problems associated with the wide variation of electromyograph amplitude and background noise depending on the specific patient's muscles selected. A pulse-width modulated signal drives the DC motor, allowing closing and opening of the prosthesis. The relationship between the motor-driver signal and the actual hand-grasp force developed by the prosthesis was measured using a hand-held grip dynamometer. The resulting force was proportional to current for moderate values of current and then saturated. The motor torque, and, in turn, the force elicited, can be measured by sensing the current absorbed by the motor. Therefore, the grasp force can be opportunely limited or controlled. The cost of the only electronic and mechanical components of the electromyographically controlled hand was about US$50; other costs, such as the cost of labor to assemble the prosthesis and the production of adapters for patients, were not estimated. Keywords: electromyography amplitude measurements, electromyograph-controlled hand prosthesis, grasp-force measurements, low-cost design

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.

In order to assess the performance of digital to analog converters (DAC) the attention is generally focused on the integral nonlinearity (INL). Useful diagnostic tools to detect the causes of poor linearity are the linearity and intermodulation errors, which can be evaluated from INL measurements. Linearity and intermodulation errors highlight and quantify erroneous calibration and unwanted interactions between current sources inside the DAC hardware. Unfortunately, their estimates, especially those related to high order intermodulation errors are characterized by high uncertainty. On the base of their very uncertain value it is difficult to establish if interactions represent relevant factors or not. It is shown that by means of the analysis of variance (ANOVA) the relevance of intermodulation errors can be assessed from a limited set counting a minimum of two INL measurements. ANOVA is in fact capable of distinguishing if the variance in INL measurements has to be addressed to active factors or noise, even if the effect of each factor is widespread upon different elements of the INL array and in different combinations with the other factors.

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.

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.

The propagation channel aboard trains is investigated with reference to the propagation path loss within cars, the delay spread and the coherence bandwidth. Results show that the path loss exponent is slightly smaller than in free space, possibly due to reflections by metal walls, and that it does not depend significantly on the position of transmitter and receiver. The delay spread and coherence bandwidth depend on both the polarization and distance between transmitter and receiver while the effect of interaction is not statistically significant. The best fit for both delay spread’s and coherence bandwidth’s experimental distribution is also investigated. Results show that it does not always match models suggested in the literature and that the fit changes with the values of the input parameters. Finally, the functional law between coherence bandwidth and delay spread is determined. Results typically match expectations although the specific measurement configuration effects the model parameters.