Visualising and Logging Science and Engineering experiments
by Dermot Brabazon, Eilish McLoughlin and Philip Smyth
A virtual instrument (VI) is a multimedia tool that can be used to present information about an experiment prior to students performing it in the laboratory. What makes a VI unique is its capability to automatically log experimental data as the experiment progresses. Over the last two years seven VIs have been developed using LabVIEW
software and associated instrumentation, and have been piloted with over 200 undergraduate and postgraduate engineering and science students at Dublin City University (DCU
VIs developed include:
- the moment of inertia laboratory;
- simple harmonic motion evaluation;
- load cell application;
- linear variable differential transformer (LVDT) and accelerometer examination;
- centrifugal force investigation;
- determination of beam shear centre position;
- control and measurement from an automated capillary viscometer.
Evaluation of student performance has shown improved learning while analysis of questionnaires and videotaped laboratories indicate a greater degree of student interaction with the instrumented experiments. The methodology developed, which is applicable to all discipline areas, and evaluation results are presented in this case study.
Higher education institutions need to keep pace with industrial and technological advancements. If students do not experience sufficient relevant hands-on experience within their course, they will not be prepared for the demands placed on them in the workplace. However, due to hardware maintenance and staffing costs, there can be a tendency to reduce the emphasis on hands-on experimentation. In addition, unless laboratory classes are sufficiently explicit, students can find it difficult to relate experiments to theoretical concepts.
A VI is a graphical user interface (GUI) that students use both prior to and during a hands-on experiment. The VI provides students with information on what they have to do and why they are doing it. For example, a VI might present:
- the relevance of the topic to be learned;
- an animation of how the experiment should be performed;
- a real time graph of the experimental data;
- interactive equations to be used to calculate the experimental results;
- laboratory report requirements.
Animations, images and video clips can also be embedded within a VI. This engages students and allows them to relate theoretical concepts to real world examples.
What differentiates a VI from other forms of computer based learning is the VI's data logging capabilities. Data logging allows students to concentrate on the experiment itself rather than being distracted by writing down results. This allows students to obtain the hands-on benefit of the laboratory whilst gaining a greater understanding of the concepts being presented to them.
The VIs were developed using LabVIEW software, a system specially designed to display and facilitate real-time analysis of experimental data obtained via physical sensors. For example, in order to instrument the flywheel experiment described in this case study the software was programmed to record signal counts from a rotational sensor against time and to scale these to show the rotational speed. With appropriate hardware connected, LabVIEW's capabilities include: scaling of input data; measurement and generation of high speed signal waves; event counting; and high-speed digital wave input and output. LabVIEW programs are created via the ‘Block Diagram’ by dragging and dropping virtual representations of the lab equipment. The Block Diagram then automatically generates a GUI (the ‘Front Panel’).
The first experiment to be instrumented was a first year flywheel/moment of inertia experiment. Flywheels are devices that are used to store energy (as potential energy) which can be released on demand to do mechanical work (in the form of kinetic energy). In this laboratory, groups of four or five students work together to verify and understand the concepts of moment of inertia and transformation and conservation of energy.
The VI begins with a simple home screen (see Figure 1) that is uniform across all experiments. This screen has three buttons leading to the introduction, experiment data logging, and theoretical sections.
At the end of the introduction section students are shown an animation of how the experiment will run (see Figure 2). This introduces students to the concepts covered in the experiment and allows them to gain a working knowledge of the apparatus.
Figure 1: VI home screen
Figure 2: animation section of the VIAfter the introduction students progress to the data logging screen and begin the hands-on experiment. Prior to the introduction of the VI students completed the experiment manually while recording data in their notebooks. Now, with the use of the data logging section of the VI, students capture the transitional data via the computer (in this case speed of the shaft rotation against time). The schema of operation for this section of the VI is shown in Figure 3.
Figure 3: schema for implementation of flywheel experiment data logging VI
After data has been logged, students progress to the theoretical section of the VI and calculate the moment of inertia (see Figure 4). The VI guides students through the theory and forces them to examine the physical processes that occurred during the experiment. Subsequent to the theory section students are presented with Multiple Choice Questions (MCQs) that test their understanding of the topic. The MCQs allow students to apply their knowledge to real world applications. For example, in the flywheel experiment students learn about moment of inertia and its effects. One of the MCQs asks about an ice-skater spinning at speed. Students enjoyed questions such as this, as they allowed them to apply the concepts learned to a totally different situation.
Figure 4: screenshot of flywheel theory screen
The impact of the VI was examined via data obtained from: feedback questionnaires; video evidence and heart rate monitoring during the labs; and grades from laboratory reports, MCQ tests and exams.
All 200 students who used the moment of inertia VI completed a questionnaire subsequent to the laboratory. This questionnaire was used to ascertain students' perceptions of the labs and to elicit suggestions for improvements to the VI. We found the student feedback very helpful as it provided insights that we would not have obtained otherwise. 83% of the students who undertook an instrumented experiment said that they believed it had benefited them. Students reported that they enjoyed the VI laboratories and said that they helped them to relate course work to the experiments. They said that the VIs made it easier to find their way through the laboratory. Students pointed out that the MCQ theory tests given at the end of the lab helped them to understand what they had just done and suggested that they should be made available on all experiments. Video evidence also indicates a greater degree of student interaction with the instrumented experiments than with the conventional experiments.
As well as seeking feedback from students, we also sought feedback from laboratory demonstrators. A problem with conventional laboratory sessions was that the demonstrator could not teach more than one group of students at the same time. The VI experiments allow the demonstrator to teach more than one group of students simultaneously.
The impact of the VI was also examined via analysis of average grades awarded to students who took the instrumented laboratories in comparison with students who simultaneously took part in the un-instrumented laboratories. The flywheel experiment has been run with four cohorts of students over the last two years. These groups consisted of first year engineering and physics students, totalling over 200 students. Approximately half took the instrumented version while the other half took the non-instrumented version. All of these students completed both the lab reports and MCQ theory tests mentioned above. The average percentage result and confidence interval for students taking the instrumented flywheel experiment were 77.1 +/- 4 and for the non-instrumented were 65.7 +/- 5.
Upon examination of the results of individual classes it was found that some classes attained quite similar results for either instrumented or non-instrumented classes whereas others showed a clear difference. This may be down to the overall standard of the class or to the VIs providing an environment better suited to different types of learner.
In our view, VIs have potential for both cost reductions and pedagogical benefits. VIs can allow students to gain a better understanding of what they are doing and why they are doing it. VIs can also provide a more interactive experience for distance learning students who can interact with the VI and control experiments remotely. Students readily engage with VIs and we have found that demonstrator workloads have decreased as a result. Reduced printing costs are also possible as traditional laboratory manual information is now provided within the VI.
There has been sufficient positive feedback to merit continued implementation, development and research with this type of instruction. Further work to develop the VIs will include integration of laboratory report submission via the system.
The authors would like to thank the DCU learning innovation fund and National Instruments Fellowship schemes for funding this work.
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Research student, Mechanical Engineering, Dublin City University
Lecturer, Mechanical Engineering, Dublin City University
Lecturer, Physical Sciences, Dublin City University
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