456 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 2, APRIL 2004 TransientMeter: A Distributed Measurement System for Power Quality Monitoring P. Daponte, Senior Member, IEEE, M. Di Penta, Associate Member, IEEE, and G. Mercurio Abstract—This paper describes the design and the implementation of TransientMeter, a monitoring system for the detection, classification, and measurement of transient disturbances on electrical power systems. TransientMeter relies on a common object request broker architecture (CORBA) as a communication interface, wavelet-based methods for automatic signal classification and characterization, and on a smart trigger circuit for disturbance detection. The system has been successfully applied to detect, classify, and measure disturbances in an industrial environment. Index Terms—Distributed information systems, monitoring, neural networks, power quality, power systems, power system transients, wavelet transforms. I. INTRODUCTION I N the recent years, users of electric power have detected an increasing number of drawbacks caused by electrical power quality variations. These variations already existed on electrical systems, but only recently they are causing serious problems. As a matter of fact: 1) devices used in modern electrical installations are more susceptible to disturbances with respect to the oldest ones, because they contain control systems provided with microprocessors that can suffer a large scale of disturbances; and 2) the growing use of power electronics implies more precautions to limit harmonic distortion. To improve power quality with adequate solutions, it is necessary to know what kinds of disturbances occurred. A measurement system able to automatically detect, characterize, and classify disturbances on electrical lines is therefore required. This brings up advantages for both end users and utility companies [1]–[3]. The main advantages for end users are: 1) risk avoidance, a monitoring system can detect disturbances that can cause damages to user equipment; 2) manpower efficiency, in that an automatic monitoring system eliminates time losses due to analyzing large signal records and preparing reports; and 3) process improvements, in that a monitoring system allows to identify the most sensitive equipments and, therefore, install power conditioning systems only where necessary. The main advantages for utilities are: 1) risk avoidance, a utility can show customers the effective quality of the power produced, to prove that the utilities themselves are not responsible for any damages that have occurred on a customer’s Manuscript received April 11, 2003. P. Daponte and G. Mercurio are with the University of Sannio, Department of Engineering, Benevento I-82100, Italy (e-mail: daponte@unisannio.it; mercurio@unisannio.it.). M. Di Penta is with RCOST, University of Sannio, Benevento I-82100, Italy (e-mail: dipenta@unisannio.it). Digital Object Identifier 10.1109/TPWRD.2004.825200 equipment; 2) manpower efficiency, likewise the end user, the utility can rapidly detect a problem and recognize its causes, avoiding massive personnel scheduling; 3) capital investment reductions, a continuous monitoring allows expensive power system improvements to be limited where strictly necessary; and 4) competitiveness, an efficient monitoring allows utilities, in a deregulated power market, to stipulate special power quality contracts and, in general, to offer a better product. Finally, by installing a monitoring system in the customer’s site, and allowing customer access to the power quality database, utilities can offer an important service, thus differentiating themselves from the competition. The challenge of developing software-based monitoring systems has been discussed in the recent years–analyzing architectures and features required by these systems, as well as the enabling technologies. The problem of analyzing data from power quality monitoring systems was discussed in [4]: panelists discussed different aspects such as capturing trends, as well as the architectures and installation issues of the power quality monitoring systems. Wagner et al. [5], [6] carried out an experiment aimed at identifying disturbances causing problems in production environments. Guidelines for implementing a power quality monitoring system were presented in [7] by Rauch et al., and in [8] and [9] by Parihar and Liu. Sawyer [10] discussed the evolution and the future trends of power monitoring systems, in terms of architecture, installation, and software functionalities. In [11], Makinen et al. discussed the state of the art of monitoring systems in Finland. The advantages of a software, object-oriented-based power quality monitoring system were highlighted in [12] by Qiu and Wimmer, where all the enabling state-of-the art software technologies were summarized. Leou et al. [13] presented a web-based system for monitoring steady-state disturbances and outages. In particular, the paper focused on the web technologies to adopt and their advantages. Some power quality systems, as well as algorithms and methods for disturbance detection and analysis, have been proposed in literature during the last few years. A circuit for disturbance detection, similar to that adopted for TRANSIENTMETER, has been proposed by Shakarijan et al. in [14]. The application of wavelet transform, in order to decompose the power signal and to extract the disturbance from the fundamental, was proposed in [15] and [16] by Gaouda et al. The application of the wavelet analysis for the detection and measurement of disturbances in a noisy environment was discussed in [17]. A digital signal processor (DSP)-based system to analyze steady-state power disturbances was proposed by Lakshmikanth and Morcos in [18] and [19]. Another software monitoring 0885-8977/04$20.00 © 2004 IEEE DAPONTE et al.: TRANSIENTMETER: A DISTRIBUTED MEASUREMENT SYSTEM FOR POWER QUALITY MONITORING system, tested in a pilot project inside an industrial environment in Brazil, was presented in [20]. The system aimed to measure duration and frequency of disturbances occurred. Bucci et al. [21] proposed a distributed, virtual instrument for power quality monitoring. The system, implemented in LabView™, aimed to measure steady-state disturbances (sags, swells, flickering), and also perform some time-domain analysis on transient disturbances (rise and fall time, amplitude, duration). Finally, an Internet-based system for detecting and measuring steady-state disturbances was presented by Waclawiak et al. in [22]. This paper proposes TransientMeter, a distributed measurement system for the automatic detection, classification, and measurement of disturbances affecting an electrical power system. The software design philosophy is oriented to adopt standard and open technologies. Its components are completely software implemented, except for a trigger circuit for disturbance detection and a data-acquisition board. A measurement algorithm developed by using the wavelet transform and the wavelet networks has been adopted for the automatic classification and measurement of disturbances. The paper is organized as follows: Section II highlights the characteristics of the monitoring systems; Section III describes the TRANSIENTMETER architecture; Section IV reports the wavelet-based algorithms for the disturbance classification and characterization; Section V reports numerical and experimental results. II. CHARACTERISTICS OF POWER MONITORING SYSTEMS A. Monitoring Instrument Characteristics Monitoring instruments today available continuously digitize current and voltage signals, and evaluate root mean square (rms) values of current and voltage, active, reactive, and apparent power, and harmonic distortion. These measurements are stored in a large memory inside the instrument. Some more sophisticated equipment allow a transient event to be detected: when the voltage level or the current level goes below (or above) user-defined thresholds (this means that a sag, a swell, an interruption, or an impulse occurred), then amplitude, duration, and occurrence time are evaluated. At end of the measurement, all of the collected information is printed in a report summarizing the events that occurred. The disadvantage of these instruments is that their operation strongly depends on the correct calibration of the thresholds. Furthermore, if a very low threshold is fixed and electrical lines are particularly affected from problems, an instrument’s memory rapidly fills up. However, a high threshold could cause the loss of some information. Therefore, the best way to proceed is an adaptive threshold that varies according to disturbance occurrence [23]. Some instruments can also increase their sampling rate whenever a disturbance occurs. Another remarkable characteristic is the possibility of comparing events with Computer Business Manufacturers Association (CBEMA) curves, opportunely customized [23]. 457 Finally, some instruments allow transferring acquired data to remote computers for post-elaboration and storage. Major disadvantages of existing equipments are: • cost (due to the use of complex hardware solutions); • low flexibility (hardware solutions are not very configurable and adaptable to particular operative conditions); • configuration and operation from remote locations are usually limited; • total absence of disturbance classification: where present, the instrument only distinguishes impulsive events from rms variations; • no information about time-frequency signal analysis; • The need for a large amount of memory to store samples of disturbances occurred, since, as said, these instruments cannot automatically classify the event, and therefore, users must manually examine all of the waveforms. B. Distributed Monitoring Systems In most cases, the information produced by power monitoring system has to be used in places physically different from those where the monitoring instrument has been placed. Here are some typical situations that may occur: 1) technicians may have to analyze data acquired in wind farm plants situated on the top of a mountain; 2) technicians of a utility have to monitor power quality in a customer’s industrial site, to verify if problems claimed from customer depend on power produced, or instead depend on customer’s devices faults; and 3) customers would have access to power quality data, stored into a utility’s database. First attempts of automatic data transfer relied on modems to allow downloading information directly from monitoring instruments and, in some cases, for controlling them. Now, with the growing diffusion of computer networks and internetworking, and thanks to middleware for developing distributed systems common object request broker architecture (CORBA), distributed component object model (DCOM), remote method invocation (RMI), it is possible to create monitoring systems more and more complex. Monitoring instruments are directly connected to the network, using a modem or a serial line. Data coming from these instruments flow in a database that users can access via the web. One or more control workstations are then used to drive and configure monitoring instruments and to manage the database. In the following, the main characteristics of all the components of a distributed monitoring system will be analyzed: 1) Measurement instruments: In a distributed monitoring system an instrument should be: • remotely configurable and controllable; • able to control other devices [e.g., starting uninterruptible power supply (UPS) when a certain event occurs]; • able to temporarily retain acquired data, to avoid loss of information in case of communication breakdown. 458 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 2, APRIL 2004 2) Control workstation: A control workstation should be able to supply the following functions: • configuration of monitoring instrument parameters; • start/stop of a remote measurement procedure; • gather and store data coming from remote monitoring instruments; • data analysis; • data export (i.e., paste into the clipboard, export to spreadsheets and to scientific software). A good control software should also have • graphical features (event plots, CBEMA curves, statistical graphs, trends); • possibility to generate customized reports; • possibility of software evolution without expensive maintenance operations. 3) Database server: The database management system (DMBS) should have the following characteristics: • fast and concurrent access for many users without critical performance degradation; • open database connectivity (ODBC) support; • any unauthorized access must be avoided; • transaction support. 4) Web-based data-access software: The peculiarities of the software for Web data access are: • restricted access: any user wishing to access data must login, typing his/her username and password; afterwards, he/she can only access to data of his/her own interest; • advanced query: users may set filters based on various fields, and using any logical operator (AND, OR, NOT, etc.); • disturbance plots: users may want to see (and download) directly from the browser events plots, CBEMA curves, statistical graphs, temporal trends, etc. 5) Communication channels and hierarchy: The selection of the communication channel strongly depends on monitoring instruments, connectivity functions, and on their physical locations. Some of the possible channels are: • fixed telephone lines by using a modem; • mobile communication system by using a Global System for Mobile Communications (GSM) modem; • telephone lines by using dial-tone multifrequency (DTMF) coding; • radio communication; • communication on the power distribution line: a typical example of this kind of transmission is the distribution line carrier (DLC) developed by Cannon Technologies [24]; • use of existing local-area network (LAN) or wide-area network (WAN): this is undoubtedly the most versatile way to build a distributed monitoring system. • the major advantage is the use of widely diffused protocols (TCP/IP) and middleware that allow very flexible and maintainable systems to be realized. Another very important aspect related to communication between monitoring instruments and control software is the possibility of a hierarchic communication system design. For example, if several monitoring instruments are placed on the same site, it is not convenient to supply each one with a GSM modem or with an independent telephone line. So, a computer could be used to gather all information coming from these instruments, and to periodically send information to a control workstation using a common telephone line. III. ARCHITECTURE OF TransientMeter A. Overview Let us now describe the main characteristics of the proposed monitoring system. Its components (including monitoring instruments) are completely software implemented, except that a trigger circuit for disturbance detection and a data acquisition board. TransientMeter uses pre-existing Internet/intranet as a communication channel, and it is composed of the following components (Fig. 1). 1) Monitoring workstations, on its turn composed by: • a trigger circuit, able to detect transient events on the electrical signals; • a data acquisition board, driven by the trigger circuit, that acquires (using pretriggering mode) all of the detected disturbances: in the current version, a National Instruments PCI 6024-E is used; • a software component, named TRANSIENTMETER Server (implemented using Borland C++ Builder 4.0), that processes the digitized signals and sends results to the control workstation. 2) A control software, simply named TRANSIENTMETER (also implemented using Borland C++ Builder 4.0), used to: • configure measurement parameters; • initialize remote monitoring workstations; • start/stop measurement procedures, in manual or automatic mode; • gather data coming from remote monitoring workstations and store them into the database; • process signals coming from text files or wave files; • query and manage the database. 3) A database, containing information about measurements made and events occurred. 4) A web-based software, named TransientMeter Web (implemented with the server-side scripting language PHP), that allows remote queries to database, shows results and allows downloads of event samples in text format and event plots in GIF format. DAPONTE et al.: TRANSIENTMETER: A DISTRIBUTED MEASUREMENT SYSTEM FOR POWER QUALITY MONITORING Major advantages of the TransientMeter architecture are: • it contemporaneously detects and classifies disturbances; • disturbances are extracted from electrical signal fundamental; • it is possible to select those disturbances the system has to detect (e.g., only some types of disturbances, only disturbances having a given amplitude and frequency); • it is possible to store into the database only extracted disturbances or only disturbance parameters (without waveform recording, therefore saving space); • the system is provided by a function that periodically calculates statistics on the current measurement, removing from the database event details and storing on it only these statistics–this is important for saving space in case of long monitoring sessions; • automatic start/stop of measurements, programming a list of timers; • distributed architecture able to support monitoring workstations that dynamically register themselves on the control workstation to notify their presence; • advanced query functions present in the control software and in the web software. Fig. 1. Architecture of TRANSIENTMETER. Fig. 2. Database entity-relationship model. 459 B. Database Architecture Database entity-relationship model is shown in Fig. 2. Entities present in the database are the following. 1) Monitoring site: it represents a generic monitoring site. Attributes are identifying code, description and state (On or Off); 2) Measurement: it represents a measurement, executed on a certain site, and composed of a certain number of events. Attributes are: identifying code, date and time of start and stop, configuration parameters (sampling rate, monitored phases and quantities), and number of disturbances detected; 3) Event: it represents a disturbance detected during a measurement. Attributes are phase on which the disturbance has been detected, quantity measured (voltage or current), date and time of occurrence, type of event, amplitude, duration or frequency, samples of disturbances extracted from fundamental, and added to fundamental (both stored in blob fields). Relationships between entities are as follows. 1) Executed On: relates the Monitoring Site entity to Measurement entity, specifying on which monitoring site a measurement was performed; 2) Detected: relates Measurement entity too the Event entity, specifying events detected during a particular measurement. C. User Interfaces As shown in Fig. 3, TransientMeter has a Multiple Document Interface, composed of the following windows: • a window used to select sites where to start/stop a measurement; • a window containing a row for each measurement; • a window for each active measurement, containing a row for each event that occurred in that measurement; • event plot windows; • statistics windows. Moreover, the instrument is provided with a panel used to control the state of the system, to monitor the number of events that occurred on a certain site, and to manually start/stop the measurements. When users access to TransientMeter Web, they can set up filters, submit a query, and then browse results. Clicking on each row of the query result page, it is possible to plot events (extracted or added to the fundamental). 460 Fig. 3. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 2, APRIL 2004 Fig. 4. CORBA architecture. Fig. 5. Measurement algorithm. TRANSIENTMETER user interface. D. Communication Interfaces The interface between control software (TransientMeter) and monitoring software (TransientMeter Server) has been built using a CORBA architecture. One of major advantages deriving from the use of CORBA is the great maintainability and extendibility of the structure. As shown in Fig. 4, remote methods are called to configure monitoring instruments, to start/stop a measurement, and to read processed data. The object request broker (ORB) adopted is TAO (The ACE ORB) built on the component level of adaptive communication environment (ACE), an open-source framework for developing distributed architectures [25], [26]. This full-compliant ORB is particularly suitable for high-performance and real-time applications. IV. MEASUREMENT ALGORITHMS This section describes the measurement method adopted in TRANSIENTMETER, obtained by combining and improving the algorithms presented in [27]–[33]. As shown in Fig. 5, the instrument processes the signal coming from a data acquisition board, driven by a trigger circuit. After the signal acquisition, signal processing is performed by software modules dealing with: 1) classifying the disturbance; 2) calculating its duration or its frequency; and 3) extracting the disturbance from fundamental and calculate its amplitude. Let us now examine the main characteristics of each module: 1) Trigger Circuit: It compares the original signal with its low-pass version, obtained by a 70-Hz frequency cut filter. If the difference goes beyond a certain threshold, a monostable multivibrator generates a TTL pulse that drives the data acquisition board. In order to monitor several phases and quantities, many trigger circuits may be OR-connected: the output of the OR gate will drive the data acquisition board, and the outputs of single circuits will be connected to acquisition board’s digital inputs to indicate on which phase the disturbance has been detected. 2) Classification: This phase is mainly based on wavelet networks (WNs). Briefly, a WN is a feedforward neural network whose first layer’s activation functions have been replaced by mother wavelet functions, and the training algorithm (backpropagation), modifies not only neural weights and thresholds, but also scale and translation parameters of wavelet nodes. This kind of network can extract time-frequency information (very useful for transient analysis) from the signal. Besides, a simple neural network can only extract waveshape information. The classification block adopted in this paper is able to classify the following transient disturbances: momentary interruptions, oscillatory transients, and impulsive transients. 3) Module for Disturbance Duration Estimation: It calculates the duration of a signal singularity. Initially, the module computes the continuous wavelet transform (CWT) of the signal, and its local maximums. Then, starting from the highest scale values (scale for CWT is the inverse of frequency), each CWT maximum is connected with the nearest one at the subsequent scale. Each sequence of maximums is called “chain.” Afterwards, noise generated chains are pruned, using appropriate thresholds, based on the fact that most noise maximums have amplitude growing with frequency, while others have a smaller amplitude than those generated by the singularity. Once only two chains remain, it is possible, at higher frequencies (where CWT ensures a good temporal resolution), to calculate DAPONTE et al.: TRANSIENTMETER: A DISTRIBUTED MEASUREMENT SYSTEM FOR POWER QUALITY MONITORING distance between chains, corresponding to the disturbance duration (e.g., in case of an interruption or an impulse), or to the disturbance frequency (e.g., in case of oscillatory transient). 4) Disturbance Extraction and Amplitude Estimation: This module decomposes the signal in subbands using discrete time wavelet transform (DTWT) implemented by a tree of quadrature mirror filters (QMFs), and then each subband is reconstructed using another tree of QMF implementing an inverse DTWT (IDTWT). The 50/60-Hz fundamental sinusoid is located at the center of the first subband. Selecting the subband containing the disturbance frequency previously calculated, and adding this subband to those adjacent, the extracted disturbance is now reconstructed. After the extraction, it is very easy to compute several disturbance characteristics like peak-to-peak amplitude, rise time, etc. 461 Fig. 6. Experiment setup. V. EXPERIMENTAL RESULTS Initially, TransientMeter was tested by means of simulated signals. This phase gave the possibility to opportunely set up the several TransientMeter’s software components. Successively, experiments were performed by means of signals produced by an arbitrary waveform generator. These tests were aimed to adopt the better conditions for the trigger and acquisition phase. Finally, experiments are in progress for the monitoring of an industrial plant. Two monitoring workstations are used to monitor the disturbances produced by two motors (see Fig. 6). The workstations are driven from a remote control workstation. The purpose of the experience is to detect disturbances occurring during the motor starting and stopping operations. An example of disturbance detected during the monitoring phase (a damped oscillation occurred during motor stopping) is shown in Fig. 7. The figure reports the digitized signal, the extracted disturbance, and measurement results of the parameters characterizing the disturbance. In order to validate the measurement method, a large set of waveshapes containing all of the possible disturbances, having different amplitude and duration, was generated and analyzed with the proposed measurement instrument (the simulated waveshapes are shown in Table I). Simulations were performed adding to the signal Gaussian white noise, therefore considering signals with different signal-to-noise ratio (SNR). For the measurement and the extraction block, duration estiand amplitude estimate relative error mate relative error were computed and reported. It is worth noting that relative errors were computed with respect to the seeded disturbance actual duration and amplitude. For the classification block, the average number of successful classifications and its standard deviation were computed. The sampling frequency was fixed to 25.6 kHz and the number of samples for cycle to 1024. For all of the categories of signal considered, 100 Monte Carlo simulations were performed. Disturbances were generated in different positions with respect to the fundamental period. The duration of the transient disturbances was chosen between 100 s and 10 ms. Table II reports errors for disturbances of duration ms, and ms having amplitude 1 Vpp, for Fig. 7. Oscillatory transient occurred on motor stopping. TABLE I SIMULATED WAVESHAPES different values of the SNR. Oscillatory transients were generated with a frequency of 800 Hz and 600 Hz, respectively, with and . For the classification block, two kinds of tests were performed: varying the SNR and varying the disturbance amplitude. In both cases, the percentage of misclassifications was computed and reported. In particular, a first statistic treatment was performed generating 100 signals of different categories, and repeating the operation for different values of the SNR. Impulsive and oscillatory transients were generated with a frequency between 600 and 1200 Hz, while momentary 462 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 2, APRIL 2004 TABLE II RELATIVE ERRORS OCCURRED IN DISTURBANCE DURATION AMPLITUDE MEASUREMENT AND Fig. 8. Percentage of misclassifications of oscillatory transients for different disturbance durations and frequency. TABLE III PERCENTAGE OF MISCLASSIFICATIONS FOR DIFFERENT SNR TABLE IV PERCENTAGE OF MISCLASSIFICATIONS OF MOMENTARY INTERRUPTIONS FOR DIFFERENT DISTURBANCE DURATIONS interruptions were generated with a duration between 1 and 3 ms. Results are shown in Table III. A second statistical test was performed producing 100 signals affected by momentary interruptions in different positions, and repeating the operation for different durations of the interruption and itself. Results are reported in Table IV for both dB. A similar test was finally performed, generating 100 signals affected by impulsive transients and 100 affected by oscillatory transients, determining the number of correct classifications for different values of the disturbance amplitude. Results were very similar for both oscillatory transients (shown in Fig. 8 dB) and for impulsive transients. for VI. CONCLUSION TransientMeter revealed to be, during all of the experiments performed, particularly effective in the automatic classification and characterization of transient disturbances. With an appropriate calibration, the system may be used in any operational environment. The use of a CORBA architecture to allow communication between control workstation and monitoring sites makes the software easily maintainable and extensible. In particular, the ACE-TAO platform has revealed itself appropriate for the scope, since it was specifically designed for real-time applications. Furthermore, TransientMeter is particularly cheap (it uses only a simple trigger circuit, a low-cost data acquisition board, and some medium-level personal computers). Future improvements of the system are related to: 1) improve the developed measurement method, introducing adaptive thresholds for wavelet neural network and automatic calibration of thresholds used in the duration estimation; 2) add modules to detect, classify, and characterize other kinds of disturbances such as harmonic disturbances, flickering, etc.; 3) use dedicated hardware [e.g., parallel DSPs for real-time signal processing]; 4) build an expert system able to detect disturbance causes and propose adequate solutions. ACKNOWLEDGMENT The authors are grateful to Edison Energie Speciali S.pA and I.T.I.S. “Bosco Lucarelli” for the collaboration given during the experiments. REFERENCES [1] Recommended Practice for Monitoring Electric Power Quality—Draft 7, Dec. 1994. [2] Why Monitoring Power Quality? [Online]. Available: http://www.pqmonitoring.com [3] D. Sabin and M. McGranaghan, A Systems Approach to Power Quality Monitoring for Performance Assessment. 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Angrisani, P. Daponte, and M. D’Apuzzo, “A virtual digital signal processing instrument for measuring superimposed power line disturbances,” Measurement, vol. 24, no. 1, pp. 9–19, 1998. [32] S. Santoso, E. J. Powers, and W. M. Grady, “Power quality disturbance identification using wavelet transforms and artificial neural networks,” in Proc. IEEE Int. Conf. Harmonics Quality Power, Las Vegas, NV, Oct., 16–18 1996, pp. 615–618. [33] H. W. Furst, M. Pigl, and J. Baier, “An analog method for detecting superimposed power line voltage disturbance,” IEEE Trans. Instrum. Meas., vol. 43, pp. 889–893, Dec. 1994. Pasquale Daponte (M’91–SM’99) was born in Minori (SA), Italy, on March 7, 1957. Currently, he is a Full Professor of Digital Signal Processing and Measurement Information at University of Sannio, Benevento, Italy. He has published many scientific papers in journals and presented at national and international conferences on ADC modeling and testing, digital signal processing, distributed measurement systems, sensors, and transducers. Prof. Daponte is a Senior Member of IEEE Instrumentation and Measurement Society Editorial Board of the Measurement Journal, Elsevier Publisher; Working Group of the IEEE Instrumentation and Measurement Technical Committee no. 10 Subcommittee of the Waveform Measurements and Analysis Committee for the definition of the new standard IEEE-1241 “Standard for Terminology and Test Methods for Analog-to-Digital Converters.” He is also Secretary of IMEKO Technical Committee TC-4 “Measurements of Electrical Quantities” and coordinator of the IMEKO Working Group on ADC and DAC Metrology. He is Rector’s Delegate for International Relations for the University of Sannio. Massimiliano Di Penta (S’02–A’03) was born in Campobasso, Italy, in 1973. He received the information engineering degree from the University of Sannio, Benevento, Italy. He is currently pursuing the Ph.D. degree at the University of Sannio. Currently, he has been working in the Research Center on Software Technology of the University of Sannio. He is the author of several papers that appeared at IEEE Computer Society conferences, as well as papers that appeared in some software engineering international journals. His research interests include software maintenance, program comprehension, object-oriented testing, and empirical software engineering. Gianpaolo Mercurio was born in Benevento, Italy, in 1969. He receive the electronics engineering degree from the University “Federico II,” Naples, Italy, in 1998 Curreently, he is a Consultant with “Edison Energie Speciali S.p.A.,” a society of Montedison group dealing with wind power. He is also with the L.E.S.I.M of the University of Sannio, dealing with research about time-frequency representations. He teaches “Measurements for Automation and Industrial Production” with a Faculty of Engineering degree from the University of Sannio.