Using a Graphical Data Acquisition Software on Early Labs Learning

Using a Graphical Data Acquisition Software on Early Labs Learning
Maria Teresa Restivo, Joaquim Gabriel Mendes, Fátima Chouzal
Faculdade de Engenharia da Universidade do Porto, Portugal
[email protected], [email protected], [email protected]
Abstract
2 Motivation
This paper presents how some case studies, based on closed
type problems of early training on engineering
instrumentation measurements, may become somehow openended, new and motivating problems. Moreover, they turned
on excellent opportunities for integrating diversified
perspectives of the syllabus, exercising students capabilities
in experimental problem solving and highly stimulating their
creativity. And, this gain was simply achieved by just adding
the use of an easy and intuitive package of graphical software.
Complementing the main goals referred above, the objectives
of the discipline are also to promote students’ teamwork skills
and personal responsibility, either in preparing lab activities,
developing criticism, doing presentations and reports, as well
as exercising their self-organizing, conflict-solving
capabilities and, if possible, implementing some practice in
self “learning-through-teaching”. Nowadays, these goals are
among those recognized as being of great importance in
students training for their future engineering environment [2]
and [8]. The students, as well, perceived these objectives as it
was observed by the results of internal discipline inquests’
analysis.
Keywords: Experimental problem
stimulation, Graphical software.
solving,
Creativity
1 Introduction
On the 5-year degree course in Mechanical Engineering, at
Faculty of Engineering of University of Porto (FEUP), early
experimental training on instrumentation for engineering
measurements appears on a 3rd year, 2nd semester in the
"Instrumentation for Measurements" discipline. Around 60%
of the time is devoted to "hands on" laboratory activity for
involving roughly 140 students. On the lab, students are
supposed to have confirmatory practices of laws, effects and
characteristics of many measuring devices associated with
their typical signal conditioning circuits. Also, they should
get a good familiarity with equipment (either of laboratorial
and/or industrial type), measurement procedures and
methodologies, covering an extensive range of physical
quantities and metrology concepts of interest in the
mechanical engineering field.
Unfortunately, due to the excessive number of students, many
of the experimental tasks are of closed type problems, having
the students to follow well-defined procedures and guided to
reach expected results. This paper presents the authors’
perspective in converting these traditional experimental
closed type problems into “open ones”. The main idea is
making the students to deal with several theoretical and
practical concepts on measuring procedures of a physical
quantity (previously studied) and then inviting them to build a
real data acquisition application for measuring some physical
quantity, complementing it with a creative and suggestive
animation by using intrinsic facilities implemented in the
software. This type of complementary task fosters the
students’ initiative, creativity and knowledge integration.
This discipline is of continuous assessment type and is based
on theoretical (1h30/week) and lab (2h30/week) sessions. In
the lab sessions the students are organized in four work
groups of three fixed elements. All the assessment criteria are
transparent to the students since the very beginning of the
semester through the complete information present in the web
page of the discipline [3].
Students’ performance in the lab (personal and group
efficiency and knowledge) contributes to the final mark
weighing 30%. Results from personal performance in written
tests along the semester (two of multiple choice type and two
traditional problem solving type), are the personal
contribution for the final mark, weighing 40%. Yet, a final
report and a 10 min presentation based in one of the lab tasks
and a poster session based on a related theme, are also
complementary assessment strategies weighing, each of them,
10%.
The lab tasks are theoretical and experimentally guided and
relevant questions related to the different matters are
included. Their subjects are mainly focused on confirming
sensors/transducers working principles, determining their
characteristics and associated measured parameters
(sensitivity, resolution, linearity, stability, histerese, etc) and
their relations with manufactures data, participating in some
calibration procedures, getting real experience with
equipment usability and their limitations and practicing early
introduction to the use of data acquisition systems. Yet, along
several tasks, the students are face to face with the calculation
of the measurements’ uncertainties, which is of a tremendous
importance but, generally, strongly persecuted by them. All
the theoretical and experimentally guided information,
complemented with several animations and simulations, is
supplied to the students in a CD-Rom, on the first lab
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session [7]. However, the training staff is permanently alert in
expanding the students’ perspectives, as much as possible,
either motivating any student’s personal request in extra
curriculum problem [5] as in finding ways of turning closed
problems in, somehow, “open-ended” ones. As a most
common approach in the lab sessions, the staff is constantly
inquiring correlated questions about related concepts and
methodologies, requesting short presentations, forcing the
discussions and criticism among groups, based on their final
results, conclusions and used strategies.
It is our believe that the use of PC with plug-in I/O boards,
associated to an easy data acquisition graphical software gives
the students, at any level, excellent training through an open,
interactive, flexible and friendly applications [6]. This
approach is an important goal in early experimental
engineering education, making the students active participants
instead of passive observers. Additionally, the animation
capabilities inherent to the selected software also contribute to
turn simple confirmatory problems into monitoring problem
solving, in a creative and integrating way.
Based on these considerations, an experience was
implemented in the final lab session. Some experimental setups previously studied were connected to data acquisition
systems. The students were required to build a software
application for acquiring and monitoring a real physical
quantity.
3.2 Some results
The two selected outcomes are related with a weighing
procedure and an angular velocity measurement. For both, the
proposed problem was the development of a user-friendly
virtual instrument, using a data acquisition and control system
based on a PC running the Labtech® software and equipped
with PCL-818HG DAS card (Advantech), for monitoring a
measuring system of weighing (based on a beam type load
cell) and of an angular velocity (based on a DC tachometer).
3.2.1 Weighing system
A beam type load cell, prepared by the students in one
previous class, was used in this setup. This load cell was
connected to the conditioning module Modular 600 (from
RDP), trimmed for ¼ bridge configuration. The sensitivity of
the complete system was set as 1mV/µ .
An aluminum beam with a rectangular cross section (b, h)
was instrumented with a strain gauge CEA-13-187UW-120
(from Vishay Micro-Measurements Division) at the distance
x1 from the fixed end and subjected to concentrated loads P at
the distance l from its fixed end, figure 1.
3 The case studies
3.1 Basic description
In the classroom, there are four experimental benches with a
PC based data acquisition system and a software from
LabTech (a free trial version is available in the web page of
the discipline), each of them associated to a sensor/transducer
device used for distinct measurements: a LVDT displacement
transducer, a DC tachometer, a temperature transmitter for a
K type thermocouple and a beam type load cell instrumented
with strain gauges for weighing purposes.
The final lab session has the objective of integrating all the
acquired knowledge with data acquisition system and
software and its own animation capabilities: drawing and
animation tools (colors, rotation, translation and shrink/grow),
alarm effects (color and sound) and linking procedures to the
animated objects.
The inherent facility of this software enables the students’
developments in a single lab session. During the building of
applications, several data acquisition features were
considered: analogue signal - single ended/differential;
conversion resolution – input range; signal noise - running
averages, sampling rate; conversion equations for physical
quantities to be measured, graphical scaling, etc.
Fig. 1: Fix-free beam instrumented with a strain gauge
Considering the Young Module of the material E, the
magnitude of the measured strain for the applied load P and
the dimensions of the beam referred above, the value of the
load is given by:
P (N) = E b h2 / (6 × (l - x1))
(1)
Replacing the constants’ values and using the given
sensitivity, it comes:
P (N) = 46.771 × V measured
(2)
The software provides an icon-based interface for building
applications. The developer starts by selecting the appropriate
blocks, adjusting their settings and linking them in the “Build
Time” window. The application developed looks like a
picture showing the relationships and data flow between the
required blocks as depicted on figure 2.
The demand of a suggestive animation associated with the
measurement monitoring lead to an explosion on students’
creativity! The following section presents two of the students’
solutions.
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3.2.2 Measurement of the angular velocity
The 1750 Training Unit (from Digiac) used along lab sessions
includes a DC motor coupled with a DC tachometer
employed for measuring rotating speed. The complete
sensitivity of the system (DC tachometer and conditioning
circuit) was 266.7 r.p.m./V.
In the Vision window the DC tachometer’s signal is displayed
in a trend graph in Volt, the corresponding rotating speed in
r.p.m. is visualized in an analogue meter, complemented with
an animated rotating disk, figure 4.
Fig. 2: “Build Time” window application
The “Vision” window provides the user interface: analogue
and digital displays, buttons, alarms (color and sound),
animation objects, etc. The following set of “Vision” widows
shows an animation’s sequence for three different loads,
figure 3.
Fig. 4: “Vision” window (disk animation) for two different
rotating velocities
In order to get a rotating disk matching the real rotating
velocity, an integrator block was used. This solution provides
a good visual performance either at low or at high velocities.
The “Build Time” window for this solution is presented in
figure 5.
Fig. 5: “Build Time” window application
Fig. 3: “Vision” windows (animation) for three different loads
Fig. 5: “Build Time” window application
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Summary and directions
In global terms we consider that the students have
accomplished the proposed experimental problem solving in a
very satisfactory way. In this particular task they have worked
as a team since the problem gave opportunity for strategy
discussion, decisions, some guessing interaction, ideas and,
basically, a strong determination on reaching one solution
(not a given one!) without the usual support of guidelines.
We can possibly say that this was a very short experience in
real “Active/Cooperative Learning” [4].
Implementations of deep strategies in pedagogy and
classroom management are very difficult to carry on when
working with a large number of students. But, this approach
made us understand that small changes in the lab sessions
should be put into practice, with some effort and a good
probability of success.
More difficult are the theoretical sessions. We know that
“simple presentation of information guarantees neither that
the ideas and concepts transmitted can be meaningfully
integrated into students’ existing knowledge, nor that they can
be generalise to new problems”, [4].
As Thorndike said a long ago: “The commonest error of the
gifted scholar, inexperienced in teaching, is to expect pupils
to know what they have been told. But telling is not to
teaching”, [9].
The authors know that there is still a long way to go. They
also know that creativity cannot be taught but only stimulated.
Nobody can lead someone to be creative showing what he/she
should do. And, in some sense, the creativity is subjacent to
the human capacity in solving new problems [1].
Acknowledgements
The authors wish to thank all the students for their interesting
solutions.
References
[1] Brown, R.T. “Creativity: what are we to measure?”
Handbook of creativity, New York, Plenum Press, (1989).
[2] K.J.Craig and C.C. van Waveren. “Group Learning in
Experimental Techniques: A Second Year Engineering
Course Study”, Conference on Teaching Science for
Technology at Tertiary Level, CD-Rom edition, Paper
Session, (1997).
Multidisciplinary Engineering Problem”, 2002 ASEE Annual
Conference & Exposition Proceedings, CD-Rom edition,
Session 2793, paper 2029, (2002).
[6] Maria Teresa Restivo and Joaquim Gabriel Mendes.
“Automated System for Educational Training on Punching
Process
Characterization”.
National
Instruments,
Education/Mechanical
Engineering,
User
Solution
nº361318A-01, (1998).
[7] Maria Teresa Restivo, Maria da Fátima Chouzal,
Fernando Gomes de Almeida, Joaquim Gabriel Mendes and
Jorge Manuel Reis. “Laboratórios de Instrumentação para
Medição: Aplicações na área da Engenharia Mecânica”
(Instrumentation
for
Measurements
Laboratories:
Applications on the Mechanical Engineering Area), 2nd
Edition, Universidade do Porto, ISBN 972-8025-16-5, (2003).
[8] Chiang Shih, Patric Hollis and George Buzina. “The
Development of a Dynamic Systems Laboratory and the
Implementation of Learning-Through-Teaching Concept”,
2002 ASEE Annual Conference & Exposition Proceedings,
CD-Rom edition, Session 1526, Paper 1876, (2002).
[9] Thorndike, E.L. “A First Book, Education”, New York,
Macmillan, (1912).
Maria Teresa Restivo
Equiv. PhD (Porto), Physics Degree (Porto)
Principal Research Officer, Departamento
de Engenharia Mecânica e Gestão Industrial
(Mechanical Engineering and Industrial
Management Department), FEUP.
Research interests: Applications and
Development of Wireless Transducers, ICT
in Higher Education, New Technologies for
Web Remote Control, Sensor/Transducer
Technology.
Joaquim Gabriel Mendes
MSc (Porto), Mechanical Engineering
Degree (Porto)
Assistant, Departamento de Engenharia
Mecânica e Gestão Industrial (Mechanical
Engineering and Industrial Management
Department), FEUP.
Research interests: Applications and
Development of Wireless Transducers,
Micropositioning, New Technologies for
Web Remote Control, Sensor/Transducer
Technology.
[3] http://www.fe.up.pt/~trestivo/im/welcome.htm
[4] Susan Ledlow, Janel White-Taylor and D.L.Evans.
“Active/Cooperative Learning. A Discipline-Specific
Resource for Engineering Education”, 2002 ASEE Annual
Conference & Exposition Proceedings, CD-Rom edition,
Session 2793, Paper 1787, (2002).
[5] José Couto Marques, Maria Teresa Restivo, Pedro Portela,
Ricardo Teixeira. “Cooperative Teaching Exploring a
Maria de Fátima Chouzal
PhD (France), MSc (Porto), Electrical
Engineering Degree (Porto)
Assistant Professor, Departamento de
Engenharia Mecânica e Gestão Industrial
(Mechanical Engineering and Industrial
Management Department), FEUP.
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Research interests: Applications and
Development of Wireless Transducers,
ICT in Higher Education, New
Technologies for Web Remote Control,
Sensor/Transducer Technology.
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