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Multidisciplinary Engineering Laboratory Experiments R. King, T. Parker, T. Grover, J. Gosink, and N. Middleton Engineering Division, Colorado School of Mines (CSM), Golden, CO 80401 Abstract - CSM is developing a series of three laboratory motion, vibration, displacement, data analysis, and error courses that is horizontally integrated to replace analysis. More details are available in [2]. Experiments traditional discipline specific laboratory courses in utilize computer data acquisition, thermistors, strain gages, electrical circuits, fluid mechanics, and mechanics of pressure transducers, flow meters, power supplies, digital materials. The objective is to provide a more realistic, multimeters, oscilloscopes, filters, amplifiers, and linear industrial experience by integrating components from displacement transducers. As small systems are developed several engineering disciplines and develop life long with these topics, students specializing in electrical, learning skills. This paper describes the multidisciplinary mechanical and civil areas begin to understand the experiments in the first course and the student’s commonalties in and relationships between their assessment. Experiments are also vertically integrated into disciplines. complex systems over a three-course sequence. This These topics, devices, and skills were chosen to vertical sequence moves students from a controlled represent inherent components of more sophisticated engineering science laboratory environment to less systems that will be covered during the three semester controlled engineering design environments while data course sequence. For example, thermistors, strain gages, analysis sophistication increases. Even though controlled pressure transducers, flow meters and linear displacement conditions are used in some experiments in the first course, transducers will simultaneously provide system data in students are not led sequentially through the steps MEL III to monitor performance of a testing machine while necessary to complete the experiment. Rather they are determining the stress/stain properties of a specimen. encouraged to develop the skills which foster life long The sequence also moves students from a controlled learning. In the vertical integration, the first course engineering science laboratory to less controlled bridges basic science and engineering science, the second engineering design environments while data analysis transitions between engineering science and engineering sophistication increases. For example, strain gages, design, and the third prepares students for industrial accelerometers, data acquisition and data analysis are projects. studied in MEL I experiments. Later they will be used to gather data from off road paths to improve suspension Introduction designs for the mini-baja student-competition vehicle. Even though controlled conditions are used in some The Fund for the Improvement of Secondary Education experiments, students are not led sequentially through the (FIPSE) within the Department of Education along with steps necessary to complete the experiment. Rather, they several companies is providing resources to develop a are given a group of objectives to accomplish, training in multidisciplinary engineering laboratory (MEL) for the skills necessary to use the required tools, and engineering students [1]. The series of three laboratory encouraged to design their own experimental procedure and courses (MEL I, II, & III) replaces traditional laboratories to be inquisitive. The instructor moves around the room, in electrical circuits, fluid mechanics, and mechanics of coaching the students through the experiments. This materials in order to provide a more realistic, industrial encourages higher level thinking skills that make students experience by integrating components from several life long learners. engineering disciplines. We connect each experiment to one or more lecture Our goal is to prepare students for the real practice of courses common to a variety of engineering disciplines. engineering by integrating disciplines, skills (wiring, Consequently, the introductory experiments bridge basic programming, experimentation, data analysis and science and engineering science. The second laboratory modeling), and methods (discovery, evaluation and transitions between engineering science and engineering investigation) on a foundation of underlying principles design, and the third laboratory prepares students for (laws of conservation, continuity and equilibrium). We industrial projects they might see in their first full time integrate disciplines horizontally and build experimentation employment. and thinking skills vertically. To accomplish the above, we set the following This paper describes the MEL I horizontally integrated guidelines for MEL experiments: experiments in bridge circuits, amplifiers, filters, thermal properties, stress and strain, pressure, flow, harmonic N All experiments should use systems. Even when a limited solutions so sophomore level students are not component is learned, it is learned in an applications overwhelmed in this one credit hour course. context. Some universities have added innovative laboratory N The exercises have many open-ended elements. Student courses that cover one technical topic applicable to multiple teams are encouraged to learn on their own and bridge the disciplines. For example, the Optoelectronic laboratory gap between experimental resources provided and course at Bucknell combines elements of electrical expected results by developing their own procedures. We engineering, materials science, optical engineering, do not give procedural steps. chemistry, and physics [6]. WPI offers a course in N We don’t attempt to teach students how to use every communications systems to students from multiple instrument, software package, or sensor that they might programs [7]. The University of Alabama Foundation encounter during their working careers. Coalition Program developed a junior level N We incorporate reverse engineering. multidisciplinary course in dynamic data acquisition and N We supply manufacturer specification sheets rather than analysis [8]. The MEL sequence differs by integrating extract critical information for the students. horizontally and vertically without adding new courses. N Students discover relationships by observing how systems MEL does not stress one topic throughout the course; each react to varying inputs. experiment integrates two or more engineering N Students evaluate competitive devices. fundamentals. N Students develop models to predict performance. Mechatronics is an inherently multidisciplinary topic N Students diagnose (investigate) unpredicted outcomes. covered by university laboratory courses [9]. At GMI, N Students practice communications skills with required students explore sensors, motors and electronic components reports, results forms, laboratory notebooks, team and interface a physical system to a personal computer. collaboration, and interviewing experts (the lab MEL I doesn’t cover control, but it will be introduced as instructor). part of the more sophisticated sequence of experiments in MEL III. Others have integrated math, physics, and engineering Comparison with Other Innovative Laboratory fundamentals. In the Foundation Coalition program at Courses Arizona State University, students design and calibrate a squash-ball slingshot, have a bungee-cord egg drop Some universities have courses dedicated to data acquisition competition, identify an unknown shape (cube, cylinder, or for students in multiple disciplines [3,4]. We considered hollow cylinder) contained in an opaque spherical plastic developing several experiments to exclusively teach shell [10]. These projects are similar to MEL I, except they computer data acquisition in the initial weeks of MEL I. are not part of a three course vertically integrated sequence. However, we chose to integrate data acquisition with Arizona State University conducts mostly unscheduled engineering fundamentals, teaching data acquisition along experiments for 11 electrical engineering courses in a single with the applications in each experiment. Consequently, we large room that is open 74 hours each week [11]. We chose do not increase the number of credit hours required for scheduled times when faculty are available to coach graduation, or displace other topics in the curriculum by students through the difficulties of learning on their own adding a separate course in data acquisition. Students do without step by step instructions, and to provide better not become expert LabVIEW£ (from National Instruments laboratory equipment security. Corp.), data-flow, G-language, programmers during MEL I, but rather develop an adequate skill to gather data. We plan Administration to expand their LabVIEW skills in MEL II and III. To encourage higher level thinking skills, some Twenty-five students were divided into teams of 3 (and one universities have open-ended project laboratories[5]. At San of 4). A group of senior students started earlier in the Jose State University, a class of 24 students majoring in semester and stayed one or two weeks ahead of the main EE, Materials Engineering, Chemical, Mechanical, and pilot group, so our experiments were tested three times, other Engineering disciplines process device wafers in once by the seniors, once by the professor, and once by the student teams. CSM has open ended projects in the pilot class. Students worked 1-4pm on Wed afternoons. Freshman and Sophomore projects courses and in our senior This was a small section of our traditional electrical circuits capstone design course, so we can focus on technical topics laboratory course that was asked to volunteer to try MEL I. in MEL while requiring students to practice and reinforce All but one student volunteered and he transferred to their teamwork and open ended problem solving skills. another section of the traditional lab. A few students in MEL I contains relatively constrained problems with other labs heard about MEL and transferred into our pilot course. Students began working during the third week of correct, they add a second and observe data from both the semester, and spent 11, 3-hour meetings on the MEL I thermistors simultaneously. experiments and one meeting on the final exam. We expand Because students take an introductory electrical to 14 meetings in the fall semester. engineering course co- or pre-requisite to MEL I, they Normally a graduate teaching assistant with help from design and wire a voltage divider circuit, containing a a professor teaches lab courses. However, the pilot course power suply, to interface the thermistor to the computer. had two professors, Drs. King and Parker. In addition the Students are required to plot their data and report it and division engineer, Dr. Grover, prepared equipment and the value of the constants in the thermistor equation. They assisted with design and instruction. After MEL I is are asked to report their procedure, especially as it pertains modified, graduate students and an adjunct professor will to exposing both thermistors to the same input conditions, teach 90 students divided between 3 sections in the fall covering as large a range as possible, and gathering semester with help from Dr. King. numerous data points within the range. We ask them to compare the data from the multimeter and LabVIEW so Experiment 1, Computer Data Acquisition, they will realize the time dependant nature of the data is Thermal Measurements, and A Voltage Divider much easier to capture with computer data acquisition. We ask them what they should do if the data on the computer Circuit monitor graph is difficult to read so they will understand the value of the digital indicator and grid line options in a The initial meeting of the semester involves introducing the graphical user interface. To begin thinking about errors in students to analog to digital conversion with a simple measurements, we ask for their opinion of the accuracy of thermistor and the LabVIEW graphical programming their data points. We require that they submit a sketch of environment. Programming skills are limited to their calibration apparatus emphasizing wiring and modification of existing programs (Virtual Instruments). component interfaces. The objectives are: N Wire a simple circuit and make A/D connections, N Expose students to a simple sensor, Experiment 2, Strain and Bridge N Introduce calibration, The objectives are: N Integrate thermal concepts and circuits, and N Discover how to measure strain N Practice data acquisition using LabVIEW. N Discover differential measurements Each team is provided with two thermistors. One is N Understand & wire a bridge circuit precise and we provide its calibration information. The second thermistor has an unknown response. Students are N Use an amplifier asked to calibrate the second over the range from freezing to N Compare circuit and wiring diagrams boiling water gathering data with a multimeter and with N Calculate strain from bridge voltage output LabVIEW computer data acquisition.. N Discover higher sampling rate VIs in LabVIEW The reference information contains the thermistor N Learn to save spreadsheet files in LabVIEW resistance equation: In the material supplied with this experiment, we discuss 1 3 the application to structural design and relate the material C1 C 2 ln( R ) C 3 ( (ln R) to strength of materials testing and ultimately to a MEL III T where: T = temperature (GK), R = thermistor resistance, and experiment in redesign of our Mini-baja competition vehicle C1, C2, and C3 are constants. suspension. Additional reference material explains the fundamentals We also make the connection to science courses and of computer data acquisition, and LabVIEW basics like provide reference material like: In one dimension, 0=/l/l, panels, menus, help features, location of example virtual and Resistance, R = 7l/A, where: 7 = volume resistivity of instruments: G programs (Vis), editing, tools menu, the material, l = conductor length, A = cross sectional area. programming elements: loops, arrays, Graph functions, 0t = -0, 3, where: 3= Poisson's ratio, 0t = transverse strain, array functions, and a customizing graphs to make a good and 0, = axial strain. user interface. Rnew = 7L(1+0)/(A(1-30)2). Student teams are asked to locate an example LabVIEW The strained and unstrained resistance provide the virtual instrument (VI) that correctly graphs one channel of following ratio assuming 7 is constant: a signal generator output. To learn the use of a function 'R (1 0 ) 1 | (1 0 )(1 230 ) 1 | 0 (1 23 ) generator, they are asked to use the function generator as a R (1 30 ) 2 known input to test their VI. After they complete one graph 'R where Fg = the gage factor Fg0 R We also provide a manufacturer’s specification sheet for 12. Explain the difference in strain precision with hardware the strain gages, the pin outs for the amplifier, etc. The and software amplifiers. following shows an example of bridge reference material provided: Experiment 3, Oscillations and Thermal Expansion The objectives are: x Extend strain measurements to the time domain. x Integrate experiments 1, 2, and 3. x Discover frequency, period and damping properties of a vibrating beam x Compare software and hardware amplifiers x Measure temperature and strain simultaneously Students study the LabVIEW VI provided using the Help Figure 1. Strain Gage Bridge Circuit feature. In addition to previous lessons, they learn how to In balance, R1 + Rpot + R2 = R3+ Rpot + R4. Assume write data to a file, scan waveforms and use the case R1 = R2 = R3 = R4 >> Rpot . Current in each branch = I structure. They add a feature that allows them to view the I = V / (R1 + R2) = V / 2R. data before deciding to save it to file. V1 = V / 2R * R = V / 2 and R4 = R + 'R. They used the Experiment 2 beam, weights, strain gage, V2 = V/(2R + 'R) * (2R + 'R) = V/2 * (1 + G)/(1 + G / 2) bridge circuit, and amplifier. They deflected the beam and where G = 'R / R, released it, causing oscillation and gathered data with (1 + G) / (1 + G / 2) | (1 + G) * (1 - G / 2) hardware and software amplifiers. They study damping by V2 = V / 2 * (1 + G / 2) adding weight to the beam. The following reference V out = (V2 - V1) = V / 4 *G = (V /4) * ('R / R) material was provided: We provide students with a small flexible beam, with (3EI / l3) G = m dG / dt2 and G = A sin (Z2t + I), strain gages mounted on top and bottom, to clamp to their or y = Acos(Zt+G) where: lab benches. They attached a series of weights to the end of y = displacement at time = t from an equilibrium position, the beam to deflect it, and measure the change in strain A = Initial (maximum) displacement, G = phase constant, Z gage resistance, then measure the bridge voltage, and = angular frequency = (k/m)1/2 , where k = force constant finally the amplified voltage. and m = mass. At a point x on the beam, We provided the students with a VI and asked the teams M=P (l - x), where M = moment and P = Force to explore it with the Help features and modify it as Stress at the top of bottom of the beam = V = M c / I, necessary. Where: c = h/2, I = bh3 / 12, b = beam width, and The student teams verify the linearity of the strain gage h = beam height and check the gage factor. We continually ask students to Strain = H = E V, where E = Modulus of Elasticity or consider accuracy and errors. In this lab, the reference Young’s Modulus (Y). material and the reporting form asks them to consider Next, students used a pair of strain gages and a digitizing resolution. thermistor to measure the thermal coefficient of expansion The following questions are asked in the report form for an unknown test specimen. They were given a quartz submitted after completing the experiment. specimen with known thermal expansion coefficient and the 1. Report the resistance data from DVM measurements. following reference: 2. Should the DVM input impedance be large? why? 'R / R «i = [EG + ( Di - DG) FG] 'T, where: 3. Explain why a voltage is applied to the bridge? i = unknown or known material, EG = temperature 4. Report the bridge voltage measurements. coefficient for resistivity of the strain gage, D = thermal 5. Compare the DVM and the bridge measurements. expansion coefficient for the test specimen (i) or the gage, 6. What excitation voltage would be optimum? Go. 7. Plot strain precision vs. excitation voltage. The results form required the students to: 8. Predict bridge output when gage is moved to other 1. Determine the minimum detectable strain with and branches of the bridge. Verify experimentally. without the hardware amplifier. 9. Explain how to use the sign of the signal change to 2. Compare data precision in EXCEL or LabVIEW. determine which strain gage is on top of the beam. 3. Graph and report the oscillation period and frequency. 10. Show the effect of two gages vs. one in the bridge. 4. Report procedures that would increase accuracy. 11. List and quantify each error. 5. Evaluate the effect of weight on oscillation. 6. Relate force constant and frequency. 7. Determine ,. 3. Give alternatives for 2, and justify their choice. 8. Show how an additional thermistor reduces error in ,. 4. Redesign the gage for a range of 250 psi. 9. Explain why quartz was a good thermal reference 5. Redesign the gage to provide 1% accuracy. material. 6. Redesign the gage to build a transducer. 10. Describe the data acquisition program. 7. Explain their calibration procedure. 8. Calculate the mass of air in the calibration system. Experiment 4, Pressure Transducers 9. Report data in EXCEL tables. 10. Submit calibration curves for each transducer. The objectives are: 11. Specify linearity, sensitivity, hysteresis, zero (null), and repeatability errors. N Reverse engineer and redesign a gage 12. Report the errors in the calibration system. N Calibrate a pressure transducer 13. Define the damage point of the tuna can transducer. N Discover hysteresis 14. Explain the damage mechanism and effect on errors. N Analyze Errors 15. Compare predicted and actual strain of can transducer. N Understand gage and absolute pressure 16. Calculate Vout of the bridge at 1.0 psi. N Understand different methods of describing accuracy 17. Calculate appropriate dimensions and sensitivity error The reference material explains the common units of of a 100-psia-aluminum transducer. pressure, and that the compressibility of a fluid is: 18. Report measurements from the manometer experiments k = -(V/V)/P, where: k = compressibility, and plot error vs. depth. V/V = fractional change in volume, and P = pressure. 19. Report the data from the differential measurement Pressure from the weight of a column of liquid: experiment. P = Po + 7gh where: Po is initial pressure at the top of the 20. Calculate specific weight for water and salt water from column (usually atmospheric pressure), 7 = density of the absolute and differential measurements. fluid, and g = gravitational acceleration = 9.81 m/s2. Additional reference material explains that pressure Remaining Experiments in MEL I measurement device accuracy is presented as zero level (null), sensitivity, linearity, hysteresis, and repeatability. The above provided details from 4 of 9 experiments. To Students disassemble and reverse engineer a low comply with FIE page limitations, we refer you to [2] for accuracy vacuum dial gage that uses a Bourdon tube. They details of experiments on: receive a box of parts including a tuna can with strain gage N Accelerometer, function generator, Nyquist mounted to an aluminum plate, a long plastic pipe, some N Microphone - filters, oscilloscope hose, a valve, a yard stick, a manufactured pressure N Flowmeters, Hall Effect, Scaling Laws transducer, and some Teflon £ tape. They are asked to assemble these pieces into a system that will calibrate both N Rotary and Linear Transducers pressure transducers and determine linearity, zero (null), N Final Exam sensitivity, hysteresis, and repeatability errors. Reference materials contain the approximate stress on the cylindrical Assessment surface of the can: 8 = 0.75pa2/h2, where p = pressure, a = radius and Our assessment data comes from multiple sources: h = thickness N Survey Instrument (see [2] for list of questions) Students determine the pressure that damages the tuna N Exam Questions can transducer. They also estimate the dimensions and N Independent Evaluator Classroom Observation accuracy of a transducer made from aluminum instead of N Focus Groups Led by Independent Evaluators steel, with a range of 0 to 100 psia. N CSM Student Evaluation Forms Students also investigate manometers and differential The independent assessment team of faculty from other manometers to measure the specific weight of water, salt departments at CSM Dr. Pavelich, Chemistry, Dr. Olds, water, and an unknown fluid, using a variety of depths. Liberal Arts, and Dr. Pang, International Studies, used They plot the error in measurement as a function of depth in focus groups, classroom observations and a student survey the fluid, consulting an extensive reference on random and to gather comparative data between MEL and EG383 ( the systematic errors to determine how different errors in an traditional electrical circuits laboratory). They concluded experiment should be combined into a total error estimate. that MEL I definitely met its goals; it caused more and The students: deeper learning, with obvious integration of topics and 1. Explain the vacuum gage working mechanism. student excitement about the experience. However, they 2. Show how make it into a positive pressure gage. were concerned that MEL may be at the extreme end of what students can handle. Specific statements heard by the three assessors were: References N MEL is open-ended, EG383 is cookbook, N MEL forces critical thinking and deeper learning, 1. Middleton, N., S. Glaser, J. Gosink, T. Parker, and R. N MEL focuses on how to learn, EG383 on what to learn, King, 1996, “An Integrated Engineering Systems N Only MEL integrates circuits, fluids and strengths; Laboratory,” FIE Proceedings paper 7c2.5, 1996. N MEL students have an excitement about the experience 2. King, R., T. Parker, J. Gosink, “A Multifaceted that EG383 students do not, Engineering systems Laboratory,” FIPSE Annul N MEL is perceived as much more "real-world", Report, Dept. of Education, 1997. N MEL students use teamwork in a more sophisticated 3. Eaton, J. K., “Computer-Based, Self-Guided Instruction fashion, in Laboratory Data Acquisition and Control,” FIE N MEL teaching is more Socratic (coaching, not telling) Conference Proceedings, 1992, 5pgs. N MEL open-endedness requires much more teacher time 4. Ojha, A. K., “Data Acquisition Experiments,” N MEL creates a higher frustration level than needed. IEEE SOUTHEASTCON Proceedings, 1996, p 533- N The background supplied at the start of a MEL 536. assignment often seems overwhelming. 5. Allen E.L., A.J. Muscat and E.D.H. Green, N Information may have been incomplete or inaccurate in “Interdisciplinary Team Learning in a Semiconductor some MEL assignments. Processing Course, FIE Proceedings Paper 6a3.1, N Non-Engineering students felt their background was 1996. inadequate for MEL and it was inappropriate to their 6. Lord, S. M., “An Innovative Multidisciplinary Elective needs. on Optoelectronic Materials and Devices,” FIE N There may be too much depth expected or too many Proceedings Paper 3a4, 1996. assignments for success with less devoted faculty. 7. Orr, J. A., D. Cyganski, and R. Vaz, “A Course in N All students learned in MEL but many seemed disturbed Information Engineering Across the Professions,” FIE by their rate of learning being slower than that of others. Proceedings Paper 6b1.1, 1996. They lacked confidence that they could do the work on 8. M c Inerny S. A., H. P. Stern, and T. A. Haskew, “A their own. Multidisciplinary Junior Level Laboratory Course in Dynamic Data Acquisition,” FIE Proceedings Paper Conclusion 7c2.2, 1996. 9. Mariappan, J., T. Cameron and J. Berry, Because MEL caused more and deeper learning, with “Multidisciplinary Undergraduate Mechatronic obvious integration of topics and student excitement, the Experiments,” FIE Proceedings Paper 6b1.2, 1996. CSM Undergraduate council approved MEL I to replace the 10. Roedel, R., M. Kawski, B. Doak, M. Politano, S. traditional circuits lab. We plan to improve MEL I and Duerden, M. Green, J. Kelly D. Linder, D. Evans, enhance the connection with physics over the summer of “An Integrated, Project-based, Introductory Course in 1997to address the assessment concerns. MEL I will be Calculus, Physics, English, and Engineering, FIE offered in fall 1997 to 90 students divided into three Proceedings, 1996. sections. We will pilot and assess MEL II, fall 1997, and 11. Palais, J. and C. G. Javurek, “Arizona State University MEL III spring, 1998. Electrical Engineering Undergraduate Open Planned topics for MEL II are: Laboratory, IEEE Transactions on Education, v 39, n 2, May 1996, p 257-264. N earthquake simulation N fluids network N organ pipe N acoustic velocities in different media N strengths test machine hydraulics and electrical power N total station surveying Planned topics for MEL III include: N Mini-baja suspension N Mini-baja GPS and digital mapping N Pathway Bridge N Fluids Processing Circuit Control N Strength of Materials Testing System