NIWeek98 Annual International Conference, National Instruments, Austin, TX, 1998.
NIWeek98 Conference Proceedings CD: (c) 1998 by National Instruments.
Integration of Data Acquisition and LabVIEW®
in Experimental
by
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The challenge:
The solution:
Introduction
"I hear…and I forget! I see…and I remember! But, I do…and I understand!" The best way to teach students is the hard way by example, i.e. by doing, not by talking about doing. Experimental method courses should be aimed in that direction, i.e., to help unlock students' imagination and show them how to apply their theoretical knowledge for solving open-ended problems in laboratory and the real-world. The emphasis in modern engineering education is placed on design and experimentation, and in particular on how to make use of the latest technological developments: sensors, transducers, data acquisition and control integrated boards, computers, Internet, etc; please see the References.
What have been implemented in engineering experimentation courses? The PC based instrumentation and analysis applications are a promising solution
At the Department of Mechanical Engineering at Northern Illinois University the two experimental methods courses have been changed to emphasize design and new-technology. Through the set of typical lab experiments, the basic sensors, transducers, instruments and measurement techniques were presented. Then, the students were assigned individual lab projects, with objectives to design and perform rigorous experiments with thorough engineering and uncertainty analysis and synthesis with critical judgment and creative thinking. Finally, the students wrote technical reports, according to the standards and customs in the profession, presented their projects in class, and had small class-groups perform their projects as per their design and under their leadership. The over-all students’ learning experience was unique and invaluable.
More importantly, the engineering students are exposed to learn and use modern instrumentation, like computerized data acquisition, along with mathematical/engineering software, like MathCAD and LabVIEW, for example. Thus, new-technology expands experimental and computational problem-solving ability, including tedious tasks, like data acquisition, (what-if) analysis, interpolation, graphing, etc. Therefore, the new-technology extends our capability and helps us do more and better in less time.
A typical data acquisition (DAQ) system may consist of transducers, signal conditioning hardware, plug-in DAQ boards, and LabVIEW® application software, see Figure 1. Examples may include monitoring and controlling complete measurement or process system, etc. The plug-in DAQ board enables computerized measurement and control of real world analog input-signals (AI, like with an oscilloscope) and generation of analog output-signals (AO, like with a function generator), as well as digital input/output (I/O) signals. The
LabVIEW® (Virtual Instrument Engineering Workbench), a graphical programming language by National Instruments®, is especially suitable for developing automated instrumentation systems using the PC plug-in data acquisition (DAQ) boards. It may be effectively used for engineering data acquisition, analysis, and presentation. The main LabVIEW advantage over the classical text/script based programming is its graphical interface where the user naturally builds a program by connecting (wiring) built-in component icons, i.e. by drawing the program's algorithm. Another LabVIEW advantage is for use to build computerized or virtual instrumentation since its input/output interface mimics the real-instrument front-panels. It is also full-fledged programming application that integrates advanced data analysi s and presentations.Virtual-Scope and Demo-Box:
In one of our Labs there is a set of computers equipped with data acquisition hardware. Each set consists of the Lab-PC+ DAQ board, cable, and Demo-box with terminals for measurements of different signal sources (± 5V, or 0-10V range), see Figure 2. The Demo-box also incorporates a simple function generator, in addition to a trigger switch and digital port LEDs. Now, in addition to usual computation and simulation, one can do REAL measurements with our personal computers. The so-called front-panel of a LabVIEW Virtual Oscilloscope application file, especially developed for use with the Demo-Box, is presented on Figure 3. Thus, a common computer is transferred into a color, multifunction, and multi-channel oscilloscope with data acquisition capability.
Figure 3: Virtual oscilloscope's front-panel
Data Acquisition-DAQ and Signal Conditioning: In another Lab we are using plug-and-play (PnP) multifunction AT-MIO-16DE-10 boards, which are configured more conveniently by software. We have a couple of DAQ set-ups with SCXI signal conditioning to measure real-time vibration of a beam (pinned on a potentiometer as an inexpensive sensor), see Figure 4, and its virtual instrument's front panel on Figure 5. More detailed description is given in Ref.[6]. Two additional units with Pentium PCs and DAQ plug-in boards with SCXI signal conditioning chases are set-up on wheeled carts as "mobile" computerized DAQ systems.
Figure 4: Measurement of a beam vibration around a sensor shaft using DAQ system
Figure 5: Virtual-instrument for measurement of real-time vibration of a cantilever beam
Concluding Remarks: New technology has an important role in education
The teaching of engineering is, in good part, abstract, verbal, deductive, and sequential, while the students tend to be passive. On the other hand, the limited experimental courses are mostly self-serving and often of the "show-and-tell" type. The classroom and laboratory instruction tends to be two different worlds. New technologies have a potential to purposefully integrate these two worlds by emphasizing their specific advantages and complementing each other, thus improving students' motivation, teaching effectiveness and overall learning experience. This is just becoming feasible now, with even brighter future, since the new-technologies are reaching needed critical mass for wide application and becoming mature and user-friendly. Experimentation course development has been a task that is not yet complete and possibly never will be, as the courses are intended to accommodate continuing advances in knowledge and technology. In search for innovative ways to teach students to utilize their formal training in science and engineering courses to solve real-world problems in the laboratory (and later in industry), often times, the multiplicity of possible solutions and inexperience of students have resulted in initial confusion and sometimes frustration. The new technology is promising to help overcome these obstacles.
Acknowledgements
The author acknowledges support by the Department of Mechanical Engineering, College of Engineering, and the Graduate School of Northern Illinois University, and the National Science Foundation support (Grant No. CTS-9523519).
References
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