A Distance Measurement Plat Dedicated to Electrical Engineering.doc

312IEEE TRANSACTIONS ON LEARNING TECHNOLOGIES,VOL. 2,NO. 4,OCTOBER-DECEMBER 2009A Distance Measurement PlatformDedicated to Electrical EngineeringNoelle Lewis, Michel Billaud, Didier Geoffroy, Philippe Cazenave, andThomas Zimmer, Senior Member, IEEEAbstractThis paper presents the remote laboratory eLab, dedicated to electrical engineering education. eLab is a flexiblemeasurement platform that permits to run more than 130 experiments in the fields of electronics and microelectronics. The instructorcan choose or create different types of pedagogical scenarios, covering teaching requirements from undergraduate to graduate levels.Furthermore, eLab implementation and use do not require any commercial software. Its reliability has been proven during manypractical classes in France and other countries. eLab is now a key component of the Bordeaux University e-Learning material inelectrical engineering. In the field of analog integrated circuits design, eLab offers a unique measurement solution, which can becombined to traditional circuit simulation sessions.Index Termse-Learning tools, remote laboratories, electrical engineering, integrated circuits, analog design and test.1INTRODUCTIONET-BASED techniques begin to be widely used ineducation. In sciences education, the experimentalmethod is an essential point of the pedagogy and studentsmust face it during practical sessions. Moreover, it is anopportunity to develop the students understanding, auton-omy, and finally, increase their interest in the topic. In theelectrical engineering (EE) curriculum, an important part isdevoted to the implementation of electrical functionsinvolved in signal processing. The physical realization ofthe function leads to nonidealities that must be quantifiedby electrical measurements. A net-based laboratory forcharacterizing electronic circuits has many advantages: Itallows sharing high-quality instruments and full-customcircuits, which could not be duplicated in several stations,for cost reasons; the net-based access allows the users tolaunch experiments and analyze the results anywhere, asoften as they want.The eLab platform is dedicated to the characterization ofelectrical components and circuits of analog signal proces-sing. In that domain, there is an important evolutionbetween the undergraduate level and the graduate level,which finally follows the thematic progression fromelectronics to microelectronics. First, the student must facewith measurement techniques and deduce some basicparameters or properties; low-cost equipment can be. N. Lewis, D. Geoffroy, and P. Cazenave are with the Electrical EngineeringDepartment, Bordeaux 1 University, 351 cours de la Libration, Talence33400, France. E-mail: noelle.lewis, philippe.cazenaveims-bordeaux.fr,geoffroycreea.u-bordeaux.fr. M. Billaud is with the Department of Software Engineering, Institute ofsufficient for that preliminary teaching. In graduate-levelcurriculum, the context becomes microelectronics and thefuture Electrical Engineer must get knowledge and practiceon Integrated Circuit (IC) design and test. In digital design,programmable devices like FPGA offer many possibilities todevelop consistent and reusable practical experiments. Inanalog design, the practical experiments are often reducedin software simulation sessions.eLab is a flexible measurement platform which givesaccess to a huge number of electronics and microelectronicsdevices or building blocks, with different types of pedago-gical scenarios, covering teaching requirements from under-graduate to graduate levels. eLab implementation and usedo not require any commercial software. Its reliability hasbeen proven during many practical classes, and eLab isnow a key component of Bordeaux University pedagogicalmaterial in EE. It offers especially a unique alternative tosoftware simulations in analog IC design and test, due tothe so-called Cyberchips.The paper is organized as follows: Section 2 summarizesthe requirements of a remote lab, taking examples in areview of existing solutions; Section 3 gives a brief historyof the previous projects that made the eLab conceptemerge. The rest of the paper shows how eLab implemen-tation choices fill the previously listed requirements:Section 4 describes the eLab hardware/software architec-ture; Section 5 develops eLab pedagogical organization andpertinence; and Section 6 proposes three examples of eLabpractical use, at different levels of the curriculum. Finally, aconclusion is proposed in Section 7.Technology, Bordeaux 1 University, Talence, France.E-mail: billaudlabri.fr. T. Zimmer is with the Department of Applied Physics and MeasurementEngineering, Institute of Technology, Bordeaux 1 University, Talence,2STATE OF THE ART AND REMOTE LABREQUIREMENTSFrance. E-mail: thomas.zimmerims-bordeaux.fr.Manuscript received 31 Mar. 2009; revised 18 June 2009; accepted 6 Oct.2009; published online 23 Oct. 2009.For information on obtaining reprints of this article, please send e-mail to:, and reference IEEECS Log Number TLTSI-2009-03-0050.Digital Object Identifier no. 10.1109/TLT.2009.45.1939-1382/09/$25.00 2009 IEEEA literature review of remote laboratories is provided in 1.All platforms implement the same software/hardwarearchitecture paradigm: a device under test is connected toa local computer which communicates with a remotecomputer (the user) through a certain middleware. ThePublished by the IEEE CS & ESNLEWIS ET AL.: A DISTANCE MEASUREMENT PLATFORM DEDICATED TO ELECTRICAL ENGINEERING313different solutions may be classified per scientific domainand per software implementation choices.In electronics domain, several platforms exist for thecharacterization of components or functional blocks 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13. Generally, a set oftypical components is connected to instruments through aspecific test fixture and the user is invited to make somemeasurement choices (input waveform, amplitude, fre-quency range, power supply, etc.), then he launches theexperiment and can display or record the results. Eachremote lab is often focused on one main topic which can be:circuit theory and Kirchhoff laws 2, 4, 8, design and testof oscillators or filtering functions 2, 6, 8, 9, 11, 12,characterization of microelectronics components 3(diodes), 5, 6 (transistors), 7 (CMOS operationalamplifiers), or characterization of HF devices 10, 13.In remote labs, software applications are needed: 1) forthe link between the device and local computer (instru-ments drivers), 2) for the link between the local and remotecomputers (middleware), and 3) for the link between theremote computer and its user (human computer interface).Two strategies mainly arise: the use of proprietarylanguages like Labview and Matlab-Simulink 3, 4, 6,9, 12 and the use of standard programming languages(Java, PHP, etc.) 2, 5, 8, 10, 13.The important features of a remote lab are: availability,security, flexibility, portability, and implementation cost.Availability is related to free user access and manage-ment of multiuser requests. When many users want toaccess the same instrument, the first in first out (FIFO)sequencing method seems to be the most efficient, becauseit avoids booking procedures 2, 5, 11, 12. However,for 10, this simple sharing access does not permit toimplement a collaborative learning strategy. Availability isalso enhanced when the users computer interface does notneed any commercial software.Security is related to both remote hardware and datatransfer on the middleware. The first point can be solved byimplementing a software validation of the users inputs, inorder to protect the instruments and devices, and thesecond point requires at least a user authentication protocol.Flexibility is related to the number of available experi-mental units and the possibility to use them in differentpedagogical scenarios, at different levels in the curriculum.It is also related to the facility to add or change anexperiment in the platform. Among the reviewed remotelabs, many offer only one or a few number of specificdevices under test. The use of a programmable device 12or a switching matrix between instruments and test boards5, 6, 7, 13 can improve the platform flexibility.Another important point is software solutions reusability10, 13.Portability is an important feature for the future systemdevelopment and possible migrations. In that respect, theplatform-independent languages and open-source compo-nents should be used as much as possible; furthermore, thatchoice limits the implementation cost.Remote on-distance measurements have been performedfor more than 10 years at Bordeaux 1 University, France.During this period, different approaches have been devel-oped. The first approach has been carried out via theEuropean project called “RETWINE,” which stands forRemote Worldwide Instrumentation Network. The basicidea was to share powerful lab instruments via the WWW14. Starting from this experience, we wanted to addressothers remote lab issues: how to design an adequateexperiment and how to introduce it in course packages.This approach has been developed in the framework ofEuropean Community SOCRATES-MINERVA projectcalled “eMerge” 15. This project was dedicated to thedevelopment of an innovative and advanced educationalnetwork structure to disseminate online laboratory experi-ments to support engineering and sciences education. Wehave examined acceptance, usability, learning effect, andusefulness. The learning effect was also measured byknowledge tests 16. The next step was to addresspedagogical aspects in the microelectronics engineeringdomain. Practical learning of analog integrated circuitdesign is often based on circuit simulations and not onreal testing. We decided to overcome this weakness byincluding a complete set of analog building blocks in ourremote platform. The basic building blocks have beenimplemented on two chips, the Cyberchips, which weremanufactured within a Multiwafer Project 17, 18. Thus,a variety of typical building blocks for analog IC designhave been made available for measurement and character-ization via the eLab platform 18. This work has beencarried out in the context of the UNIT project and is part ofits platform 19.Today, eLab is used in the curriculum of EE, in highschools or universities, for undergraduate and graduatestudents, in an open international network. Our currentmain partners are: Sfax Superior Institute of Electronics andCommunications (Tunisia), Dublin Institute of Technology(Ireland), Tampere Polytechnical University of AppliedSciences (Finland), and Catholic Polytechnical University ofBruges-Ostend (Belgium).4 ELAB ARCHITECTUREeLab is a Web-based platform which allows users toperform real electronic measurements on a wide varietyof experiments in EE.Availability was the main objective during the designphase: it is possible to run many sessions simultaneously,on the same topic, without any booking, as the systemmanages concurrent access to the hardware (instrumentsand circuits) transparently. Moreover, only standard openWeb technologies (HTML, Java, and Javascript) are in-volved and no specific software has to be installed on theuser side. So, eLab is available for students to work anytimefrom everywhere.Users of eLab are given access to so-called textbooks. A3ELABBRIEF HISTORYtextbook is a group of PDF, HTML, etc., documents contain-ing course material, documentation, and a set of proposedeLab was developed in the framework of severalEuropean initiatives.measurements about one topic. The experimental data theycollect are stored in a personal notebook.314IEEE TRANSACTIONS ON LEARNING TECHNOLOGIES,VOL. 2,NO. 4,OCTOBER-DECEMBER 2009Fig. 1. Architecture of eLab platform.A local database of accounts was first used for theauthentication of a small number of local users. Over thetime, several Single sign-on (SSO) plugins have been added.requesting the instrument server to start a measure-ment through an SOAP call,storing/retrieving the results in the users notebook.when it became necessary to integrate eLab to the Ulysse20 pedagogical platform of Bordeaux 1 University, thento the eMerge portal 21, and finally, to the Universitytop-level portal 22.Measurements are performed through a simple form-based interface; according to the textbook, users have toanswer questions about the experimental results, which arestored in a notebook to be reviewed later by the teachers.Experimental results can be seen as arrays of numbers,curves (generated by GNUplot), and also through aninteractive Java applet which provides easy calculation ofslopes near interesting points.The measurement time is relatively short (typically,20 to 40 s). Besides, students dont start measurements toofrequently because they also have to understand the coursematerial and the experimental data they collected. Conse-quently, the system load is rather low. Practically, weseldom observe more than two or three measurements inthe queue, even with 20 users working simultaneously oneLab. Most of the time, users dont have to wait at all.However, in order to attenuate the likely unpleasantexperience of waiting, a feedback is provided to the userthrough a real-time view of the on-going measurements (amotorized camera automatically zooms on the differentactive instruments), together with the list of the pending jobs.The user interface follows an object-oriented design:each type of experiment is managed by a separate objectcreated from a dynamically loaded class. This object isresponsible forSince June 2009, there are approximately 150 experi-ments managed by three main classes Freqdomain, Time-domain, and DC. The latter is by and large the most complexwith 29 subclasses to manage all the hardware configura-tions of 80 separate types of experiments.Fig. 1 gives an overview of eLab architecture.The instrument server has three layers: at the bottomlevel, each type of instrument is driven by a specific class:for example, a PowerSupply has methods to set its outputvoltage and get the current level. At the middle level, a PHPscript coordinates the work of instruments, power supplies,and switching matrix, in order to perform a type ofmeasurement. The top level presents these measurementsas SOAP Web Services.The current implementation of eLab runs on two low-end computers, with the classical Linux Apache MySQLPHP (LAMP) setup.The front-end computer runs the Web server with theeLab application; it also hosts the database with accounts,notebooks, and results.The instrument server is hosted on a local network; itdrives the instruments and the two switching matrices(through parallel and serial ports) that can operatesimultaneously, with separate queues. A specific extensionof PHP has been written in order to drive the GPIB-IEEE-488 interface card directly from PHP scripts; it is nowavailable as part of the open-source PHP5-GPIB package ofLinux/Debian 23.The switching matrix for time- and frequency-domainmeasurements connects one device/circuit under test.HTML presentation, code generation for forms, andresults displaying,users input data validation (including checkinghardware limitations),(75 among a maximum of 128) to an AC Gain-PhaseAnalyzer (HP 4194) for frequency-domain measurements,or a function generator (Agilent 33220A) coupled to adigital oscilloscope (Agilent 54621A) for time-domainLEWIS ET AL.: A DISTANCE MEASUREMENT PLATFORM DEDICATED TO ELECTRICAL ENGINEERINGTABLE 1Elab Available Resources315measurements. The device under test is also connected topower supply (Agilent 3649A).The switching matrix for DC measurements connects25 building blocks from the so-called Cyberchips to threeDC source meters (Keithley 2400) and a power supply(Agilent 3649A).5 ELAB PEDAGOGICAL ORGANIZATION ANDPERTINENCEIn this section, we will see how the previously describedmaterial can be organized in e-Learning pedagogicalresources.The current version of eLab results from a 10-year-oldhistory, and we now clearly see the interest of this tool forEE education.A set of pedagogical resources is available on eLab site,which can be used at different levels of the Bachelor orMaster curricula. They are listed in Table 1.Each pedagogical resource is associated to a textbook,which contains a summary of the objectives, a shortdescription of the circuits under test, and several prefor-matted measurement sessions. One specific experiment canbe run by the teacher, as an illustration of a theoretical course,in a multimedia equipped amphitheatre. More frequently, asubset of these pedagogical resources is used duringpractical courses by a class of students. Students are expectedto study the characteristics of circuits, make calculations andpractical measurements, and answer questions. Results andanswers are stored in the students notebooks, so they can beretrieved, analyzed, and printed later.For resources 1-7, the circuits