Using the Internet and Virtual Instrumentation to enhance the learning of Electrical Measurements Bojan Gergič, Darko Hercog, Ladislav Mikola, Vojko Matko University of Maribor, Faculty of Electrical Engineering and Computer Science
Key words: Distance learning, virtual instrumentation, remote laboratory Abstract: This paper describes an "Electrical Measurements" course that is taught at the University of Maribor, Faculty of Electrical Engineering and Computer Science. An overview is provided of the syllabus and goals of the course. It shows how Internet technologies and Virtual Instrumentation were implemented to enhance the course. The emphasis is on real experiments that are indispensable for developing skills to deal with instrumentation, and on the remote laboratory implemented with LabVIEW Remote Panels technology.
1 Introduction The Faculty of Electrical Engineering and Computer Science at the University of Maribor offers university-degree and higher professional-degree study programmes in Electrical Engineering. University-degree studies last nine semesters, while higher professional studies last six semesters with an additional semester of practical placements in industry. The Electrical Measurements course is compulsory for all Electrical Engineering study programmes, and serves as a basis for all subsequent laboratory courses. The goal of this course is to provide the student with basic knowledge about instrumentation and measurement, in order to successfully design experiments and measurement systems. Students are required to perform experimental laboratory work and write measurement reports during the course. Rapid progress in the development of information technology has an influence on teaching and learning, on the one hand, and instrumentation and measurement on the other. Conventional classes are supplemented by e-learning and remote laboratories, whilst virtual instrumentation has become widely used in measurement [1], [2]. This paper explains how this Electrical Measurements course was enhanced to accommodate this progress.
2 Application of e-learning portal The University of Maribor has established an e-learning portal which also implements a distance learning support service [3]. The distance learning support service was first introduced for higher professional-degree students on the Electrical Measurements course. It serves as the main source of information for the course and offers many different services to the student, amongst them: • main information about the course and course schedules • contact information about professors, assistants and laboratory technicians 1
• • • • • • •
contents of lecture with lecture notes laboratory work material and laboratory schedules reporting of assessment results exchange of documents group mailing and sending of SMS/MMS notes, literature, links discussion forum
The laboratory work material for each exercise contains (figure 1): • title and description • electrical schematic with pop-up photographs of instruments and measurands • instrument list with user manuals and specifications • lab procedure with films • theoretical background • spreadsheet template with pre-designed tables and graphs • template for writing the formal report
Figure 1. The laboratory work material for the exercise The publishing of laboratory work material in portal has many advantages over the traditional printed text. In the portal, students can find all the necessary laboratory work material in one place and accessible from their homes via the internet. This way they can be better prepared 2
for the laboratory work than before. It also enables them to be less reliant on the instructor during the laboratory work. The quality of laboratory work has improved because it enables teachers to publish advanced multimedia materials like films, and thus explain lab procedures more easily. It also makes it possible to update and improve exercises more frequently.
3 The laboratory work The Electrical Measurements course for the university-degree study programme takes place in the second year of study with 60 hours of lectures in the Autumn semester and 60 hours of practical laboratory work (including 15 hours of LabVIEW course) in Spring semester. In the higher professional-degree study programme the course is divided between the first and the second year of study. In the first year of study the course contains 45 hours of lectures and 15 hours of laboratory work in the Spring semester and continues in the second year with 45 hours of laboratory work (including 15 hours of LabVIEW course) in the Autumn semester. About 60 university-degree students and 140 higher professional-degree students perform laboratory work every year. In the first week the students perform two exercises which the assistant leads step by step, with the help of on overhead projector. During these two exercises the assistant demonstrates how to: • work safely • use the computer infrastructure in the laboratory • assemble the circuit • handle with instruments • prepare the equations and display the graphs in spreadsheet • write the report The students perform subsequent exercises alone and gradually become independent of the assistant. The measured values are written directly into spreadsheet with the results immediately calculated and graphically displayed. This allows easier verification of the results, and timely correction of errors. The students are required to finish the report during each exercise with the exception of the comments, which they write at home. The inclusion of report writing within the laboratory work has eliminated the copying of results, improved the quality of reports, and at the same time, relieved the students of homework. 3.1 The laboratory environment The inclusion of report writing and virtual instrumentation into the laboratory work has necessitated radical change in the laboratory setup. Ten measuring work places, designed specifically for these exercises, are composed of (figure 2): • laboratory table with built-in ordinary modular instruments such as function generator, multimeter and osciloscope • various built-in power sources • panel for measurands • PC with Windows XP and all necessary software (LabVIEW, Multisim, Matlab,...) • PCI-6024E multifunction data acquisition board from National Instruments with a connection module in front of the table • GPIB plug-in controller from National Instruments with a connector built-in table The laboratory table has enough space for those additional instrumentation and measurands used during different exercises. The computers are connected in a network which is made up of a Windows 2000 Server and Windows XP Workstations grouped in an Active Directory domain [4]. This domain is administered as a unit with common rules and procedures defined by Group Policy. Within the Group Policy tool the administrator defines and controls how 3
programs, network resources, and the operating system behave regarding the users and computers within a domain. The user profiles are roaming which means that they are downloaded to the local computer when a user logs on, and updated on the server when the user logs off. This preserves students settings when they move from one computer to another. Every student within a domain has a personal folder that is redirected to the server. Folder redirection reduces network traffic and enables a student to access his personal folder across the internet by using remote access VPN (Virtual Private Networking) connection [5].
Figure 2. The measuring work place 3.2 The LabVIEW course The concept of virtual instrumentation is to combine different hardware and software components to create a customized system for testing, measurement, and industrial automation. Software is the most important component of a virtual instrument and LabVIEW has become the most popular development tool because of its easy-to-use graphical programming environment [6]. It has the powerful display, analysis and communication capabilities required for today's rapid development of virtual instrumentation. The LabVIEW has been used for experimental laboratory work by many subsequent courses, therefore, the decision was made to incorporate the LabVIEW course into the laboratory work of Electrical Measurements. This basic course prepares students for: • using the LabVIEW to create the test and measurement applications • understanding front panels, block diagrams, and connectors/icons • using various editing and debugging techniques • using built-in functions and library programs • creating and saving LabVIEW programs and using them as subroutines • using the programming structures and data types that exist in LabVIEW • displaying and logging measured data • creating applications that use data acquisition (DAQ) boards 4
The course contains eight lessons divided over two days: Day 1 1. Introduction to LabVIEW 2. Creating, Editing, and Debugging a VI 3. Creating a SubVI 4. Loops and Charts
Day 2 5. Arrays and Graphs 6. Case and Sequence Structures 7. Strings and File I/O 8. Data Acquisition
Each lesson consists of an introduction which describes the lesson’s purpose and what the students will learn, a discussion of the topics, a set of hands-on exercises to reinforce the topics presented in the discussion, and a summary that outlines the important concepts and skills taught in the lesson. The exercises complement each other and end with temperature control application. In addition to this instructor-led course, LabVIEW Basics I Interactive from National Instruments is available online to our students in order to review the matter from home at their leisure. The students are encouraged to use LabVIEW 7 Express Student Edition for their personal educational use at home [7].
4 Implementation of the remote laboratory The conventional laboratory work was supplemented by remote laboratory experiments in order to demonstrate the communication capabilities of virtual instrumentation and to keep up with technology. These real-world experiments are available to the students all the time and could be monitored and controlled over the internet using a standard Web browser. The remote laboratory was implemented with the Remote Panels feature of LabVIEW [8]. The teacher can quickly publish the front panel of a LabVIEW application for use in a Web browser by using this standard feature of LabVIEW. Once published, the students can monitor and control the experiment which executes locally on the remote laboratory server. The student simply points the Web browser to the Web page associated with the application. Then, the user interface for the application shows up in the Web browser and is fully accessible to the student. If another student is controlling the remote laboratory, the other students are able to monitor the actions of the controlling student. Once time-out occurs or the controlling student has released control, the remote laboratory is available for the next student. It is necessary to have a free LabVIEW run-time engine installed on the client computer in order to operate a LabVIEW application using Remote Panels. If the run-time engine is not already installed on the client computer when the student connects to the remote laboratory, the LabVIEW front panel will not appear immediately but will automatically re-route the student to install the run-time engine from the National Instruments Web site. The student must have administrative privilege on the client computer in order to install the run-time engine, otherwise the installation will not start and the front panel will not show up. The equipment necessary for remote laboratory implementation was already present in our laboratory. The server is standard PC with Windows XP, LabVIEW 7.1 and PCI-6024E multifunction DAQ board. A HM 8030-3 Hameg function generator with voltage controlled frequency input (FM Input) and trigger output is used as a signal source. The FM Input is connected to the analog output of the DAQ board and used to set the frequency, which is then measured at trigger output connected to the counter gate input of the DAQ board. One of the temperature control modules that were made for the LabVIEW course is also connected to the DAQ board. Three different experiments were prepared using this equipment. The first experiment is the binary control of temperature which every student carries out during the LabVIEW course. This experiment demonstrates how this application can be controlled and monitored from a distance. The second experiment acquires a specified number of values from two analog input channels and displays them graphically. On the first channel, the sinus signal from the function generator is connected and on the second channel, the square wave from the trigger 5
output. The student can set frequency, number of samples per channel, and the sampling rate. The students can observe the effects of sampling for different frequency and sample rate settings [9], [10]. The third experiment is the measurement of elementary two-terminal circuit element's frequency characteristics (figure 3). This experiment is in direct relationship with the exercise that students perform during regular laboratory work and demonstrate them the advantages of virtual instrumentation. The student only has to logon to the remote laboratory with his name and e-mail address, perform a few mouse clicks and after only a few minutes of work he receives a finished table with the results in his e-mail box. For realization of the same experiment with classical instruments, one hour of laboratory work is usually necessary.
Figure 3. Remote front panel before beginning (left) and after finishing of experiment (right).
5 Conclusion With the application of e-learning portal the students become considerably better informed about the course because they find all necessary information in one place, accessible from any computer connected to the internet. The quality of the laboratory work has also improved because teachers can now publish advanced multimedia materials to explain lab procedures more easily and update exercises more frequently. Inclusion of report writing during the laboratory work has improved the quality of reports, and at the same time, relieved the students of homework. This traditional laboratory work has been expanded with the LabVIEW course which prepares students to use the LabVIEW to create measurement applications. This course is also the basis for many subsequent courses that use the LabVIEW. The traditional laboratory work and LabVIEW course were supplemented with the remote laboratory to demonstrate the advantages of virtual instruments that can be controlled remotely over the internet.
References: [1] Rinaldi, P.; Tinarelli, R.; Peretto, L.: E-learning applied to the degree's course in Electrical Engineering: the case of Electrical Measurement. Proceedings SPEEDAM 2004, Capri (Italy), pp. 500-505, June 2004 [2] Gustavsson, I.: Laboratory experiments in distance learning. International Conference on Engineering Education, Oslo (Norway), August 2001 [3] Ojsteršek, M.; Dinevski, D.; Klojčnik, T.: The Portal of University of Maribor. Proceedings EUNIS 2004, Bled (Slovenia), pp. 384-389, July 2004
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[4] Minasi, M.; Anderson, C.; Smith, B. M.; Toombs, D.: Mastering Windows 2000 Server 3/E. Sybex, 2001 [5] Davis, J.; Lewis, E.: Deploying Virtual Private Networks with Microsoft Windows Server 2003. Microsoft Press, 2004 [6] Bishop, R. H.: Learning with LabVIEW 7 Express. Prentice Hall, 2004 [7] LabVIEW 7 Express Student Edition. National Instruments, Prentice Hall, 2004 [8] Distance-Learning Remote Laboratories using LabVIEW. National Instruments, 2002 [9] Wheeler, A. J.; Ganji, A. R.: Introduction to Engineering Experimentation. Prentice Hall, 1996 [10] Oppenheim, A. V.; Willsky, A. S.; Nawab, S. H.: Signals and Systems 2/E. Prentice Hall, 1997
Author(s): Bojan Gergič, Ph.D. University of Maribor, Faculty of Electrical Engineering and Computer Science Smetanova ulica 17, 2000 Maribor, Slovenia Email:
[email protected] Darko Hercog, B.Sc. University of Maribor, Faculty of Electrical Engineering and Computer Science Smetanova ulica 17, 2000 Maribor, Slovenia Email:
[email protected] Ladislav Mikola, M.Sc. University of Maribor, Faculty of Electrical Engineering and Computer Science Smetanova ulica 17, 2000 Maribor, Slovenia Email:
[email protected] Vojko Matko, Ph.D. University of Maribor, Faculty of Electrical Engineering and Computer Science Smetanova ulica 17, 2000 Maribor, Slovenia Email:
[email protected]
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