Proceedings, XVII IMEKO World Congress, June 22 27, 2003, Dubrovnik, Croaia XVII IMEKO World Congress Merology in he 3rd Millennium June 22 27, 2003, Dubrovnik, Croaia LABORATORY COURSE OF ELECTRONIC INSTRUMENTATION BASED ON THE TELEMETRY OF SEVERAL PARAMETERS OF A REMOTE CONTROLLED CAR J.C. Campo, M. A. Pérez, F. J. Ferrero, M. González, J.C. Viera and C. Blanco Dp. Of Elecrical and Elecronic Engineering. Oviedo Universiy Campus de Viesques s/n 33204 Gijón (SPAIN) e-mail: campo@ae.uniovi.es Absrac A new laboraory course in elecronic insrumenaion based on he elemery of he emperaure, revoluions per minue and acceleraion of a remoe conrolled car is described in his paper. The main objecive of he course is o cover he disciplines involved in Insrumenaion, ha is, sensor use, analog and digial design, microconrollers, daa acquisiion and sofware, wihin a framework ha provides highly moivaing work. Keywords: Educaion, insrumenaion, sensors 1. INTRODUCTION Elecronic Insrumenaion course has conens largely dependen on he Universiy and counry where he course is run. Insrumenaion and Measuremen was no usually a major subjec a universiies [1], mos of which include insrumenaion, measuremen and conrol as par of he Elecrical and Elecronics Engineering curriculum. Insrumenaion and Measuremen [2], [3], [4] and [5] involves many disciplines, which urns creaing a course and deciding on conens ino a dauning ask. Engineering echnology programs ha include insrumenaion, measuremen, conrol, and similar opics really should include courses in auomaic conrol sysems, fundamenals of elecriciy and elecronics, microprocessor sysems, programmable logic conrollers, hermodynamics, fluid dynamics, chemisry, algebra and calculus, and oher areas of sudy [5]. In Spain, BSc and MSc degree courses in Elecrical and Elecronics Engineering cover no only hese disciplines bu also Neworks, Programming Languages, Power Elecronics, and so on. Mos Spanish universiies include a 45-hour final year undergraduae course called Elecronic Insrumenaion, or some such name. Elecronic Insrumenaion course includes boh, heory and pracice pars o cover is main objecives. 1.1 The heory par of he Elecronic Insrumenaion course a he Universiy of Oviedo. The basic elemens of a measuremen sysem are he sensor, he signal condiioning circui and a display o show resuls [6]. However, mos sysems are more complex and include analog-o-digial conversion, signal processing and signal ransmission before or afer digializaion (Fig. 1). Furhermore, several signals mus ofen be eiher ime or frequency muliplexed over he same ransmission channel, hereby adding o he complexiy o he sysem. Sudens who underake he heory-based course a Oviedo have already aken courses in fundamenals of elecronics, and D/A conversion and displays. Sensor Sensor Condiioning sage Condiioning sage Transmission Digial processor (a) (b) Transmission Digial processor DISPLAY DISPLAY Fig. 1. Two ypical opologies of insrumenaion sysems for single-variable measuremen: (a) digial ransmission opion; (b) analog ransmier sends daa o processor. Thus, he heory-based course essenially deals wih hose subjecs ha have no ye been sudied, i.e., sensors, he design of signal condiioning circuis, an elemenary inroducion o signal ransmission and several lecures on noise and inerference (able I). This heory-based course runs in conjuncion wih a 15-hour laboraory course. TABLE I Conens of he Elecronic Insrumenaion course in he Oviedo Universiy Inroducion o Elecronic Insrumenaion. Amplificaion. Parameers of he real operaional amplifier, oher ypes of amplifiers and noise. Filering. Sensors and heir signal condiioning circuis. Resisive sensors. Inducive and capaciive sensors. Signal generaing sensors. Crieria for sensors selecion. Signal conversion and ransmission. Elecromagneic inerference.
Proceedings, XVII IMEKO World Congress, June 22 27, 2003, Dubrovnik, Croaia 1.2 The laboraory course a he Universiy of Oviedo Tradiional educaion is based on he belief ha sudens wih solid heoreic knowledge can effecively develop ino professional engineers by raining in indusry [1]. However, significan pressure is now being brough o bear in an aemp o change his siuaion, and as a resul laboraory courses have become ever more imporan in recen years. Mos laboraory courses are based on a number of one-off experimens, in no way iner-linked o each oher. Bu, as oher engineering subjecs, Elecronic Insrumenaion involves applying a large number of differen disciplines o deal wih issues relaed o such fields (analog circui design, digial circui design and sofware developmen). The mos imporan goal of he laboraory course will be he inegraion of each discipline, insead of hem being deal wih in separae experimens. This would be exremely pracical, as experience shows ha such inegraion is no obvious o all sudens. However, a pracical, inegraing course of his ype would involve a greaer suden workload 1.3 Laboraory course objecives So, i should herefore be carefully designed so as o moivae sudens as much as possible despie his ineviable exra burden. However, despie is inegraed naure, such a course would benefi also from being divided ino several independen assignmens, or blocks, so ha a whole range of marks and assessmens is available o grade sudens by. The main objecives of his course, herefore, are: a) To design a complee insrumenaion sysem involving several disciplines b) To clarify as many conceps of he lecure classes as possible c) To moivae he sudens owards maximum progress. d) To promoe eamwork. The main resricions o achieve hose goals are a limied budge, limied ime o use he laboraories, and he limied number of credis assigned o laboraory courses. 2. LABORATORY COURSE CONTENTS To fulfil he above-menioned objecives, a projec-based course was designed along he lines of oher successful experiences [9] relaed o insrumenaion sysems. I consiss of designing a sysem, shown in he block diagram in Fig. 2 o measure several parameers of a remoe conrolled car (engine emperaure, engine r.p.m. and woaxis acceleraion), o radio his informaion, and o display all daa on a PC. Noe he similariy o he block diagram from Fig. 1b excep for he mulivariable characerisic. The laboraory course is divided ino six main work packages (WP) as we can see in Table II; sudens are grouped ino hree-person eams and each eam mus complee as many work packages as possible. TABLE II. Work packages of laboraory course. WP Descripion 1 Measuremen of he engine emperaure 2 Measuremen of engine r.p.m. 3 Measuremen of xy acceleraion 4 Daa acquisiion and ransmission 5 Compuer daa soring and visualizaion 6 Final mouning and esing All he work packages are independen o such an exen ha a eam compleing. All eams, including hose who fail o complee all he work are allowed o move on o he final ess using he remoe-conrolled car. A furher advanage of he course is ha he sequence of he work packages is quie similar o he syllabus of he lecure (Table I), allowing differen conceps deal wih during hese lecure classes o be reinforced. The firs hree WP are relaed o sensors and signal condiioning. The diagram of each circui (devoid of all values), a prined circui board and anoher diagram showing he componen locaion of each circui is given o he eam, who can opionally re-design he PCBs. These circuis mus be powered by a 9.6V, Ni-Cd baery so hey can be assembled on he car. The oupu of each circui mus be in he range of 0-5V, as his is he inpu range of he converer used on he following WP. WP4 basically consiss of programming a PIC microconroller o perform he daa acquisiion and signal ransmission asks. WP 5 consiss of programming he compuer. Finally, WP 6 consiss of mouning he sysem and carrying ou ess wih he car. The eam mus also wrie a complee repor ha mus include: - Calculaions. - The resuls. - The answers o several quesions. As far as laboraory faciliies are concerned, here is a main laboraory in he Engineering School where he sudens can work several hours a week. The number of eams is abou eigh per course and previous experience has proved ha here are no large logisic problems. There is also a basic elecronic devices sore a he school (resisors, capaciors, semiconducors, cables and he like) where sudens can acquire componens once auhorised o do so by a lecurer wihou incurring he expense in erms of boh ime and money of having o buy hem. T r.p.m. x acc. y acc. sensors condiioning circuis PIC microconroller RF TX anennas RF RX daa acquisiion and ransmission sysem Fig. 2. Sysem block diagram. daa display 2.1 Sensors and condiioning sages A P100 sensor is used o measure engine emperaure. As has already been poined ou, he diagram of he circui, he PCB and he drawing showing componen locaion as well as a brief explanaion are given o he eam. Mos commonly-used circui in elecronic insrumenaion is he unbalanced bridge and i is used for he signal condiioning circui wihou hardware calibraion. The final circui includes an INA118 insrumenaion
Proceedings, XVII IMEKO World Congress, June 22 27, 2003, Dubrovnik, Croaia amplifier and an LM336-5V as he volage reference o supply he bridge. An opical encoder is used o measure rear axe revoluions per minue. I is consiued by a 25-gap disk aached o one of he car s rear wheels (Fig. 3) so an oposwich provides a signal whose frequency is proporional o he axle r.p.m. The scale of represenaion may be changed; so, sudens can adap i o heir specificaions. Moreover hey mus add elemenary conrols o achieve wo poins calibraion o measure he engine s emperaure. Fig. 4 shows a ypical graphical inerface made wih he objecs. R.P.M Temperaure and calibraion Acceleraion Serial por Fig. 3. Cusom design for r.pm. sensor. The signal condiioning circui includes a LM2917 as frequency-o-volage converer, using he buil-in operaional amplifier of he LM2917 o design a Buerworh filer in order o apply he knowledge ha sudens acquire during lecure classes. The acceleraion measuremen sysem is based upon he sensor ADXL2 from Analog Devices. This sensor needs few addiional devices which values can be obained from daashee or changed in order o obain good calibraion wih low-cos single-urn poeniomeers. 2.2 Daa acquisiion and ransmission This work package consiss of daa acquisiion, serial ransmission and recepion by radio, and signal adapaion o he RS-232 serial por of he PC (see Fig. 2). Daa acquisiion is performed wih a PIC microconroller: 16F876. Is feaures include a buil-in 5-channel 10-bi converer and allow in-circui-serial programming. Daa are ime muliplexed and ransmied by using a low-cos RF ransmier (he Tx-Saw 433/s-z from Aurel) able o use a ransmission frequency of 433.92MHz (so far from he 40 MHz of conrol sysem working frequency of he remoe car). The radio frequency receiver (an Aurel BC-NBK model) provides a TTL compaible oupu and i is ranslaed o serial PC inpu RS-232 level specificaions by means of a MAX232. 2.3 Visualizaion The eam mus program he PC using Visual Basic o display he resuls. Programme objecs and heir basic srucure are given and explained o he sudens in order o reduce he workload for his work package. One of he objecs is for serial daa acquisiion and provides four numbers corresponding o each sensor signal. The number of bis in he objec corresponding o he ransmission may be changed according o he number of bis seleced in he previous work package. The oher objecs show he emperaure, he engine r.p.m., he x and y acceleraions, and he sum of boh acceleraions graphically and numerically. Acceleraion Fig. 4. Typical graphical inerface o display car parameers. Some sudens have considerable knowledge of compuer programming and prefer o make heir own objecs. However, he use of designed objecs is encouraged because he programming asks uses a lo of spare ime of sudens. 2.3 Mouning and esing Each suden eam assembles he whole sysem and carries ou several ess o verify he righ operaion of sysem. One of is asks is o wire he sysem in such way as o cu ou noise and inerference. Imporan principles mus herefore be applied such as proper grounding, using of wised-pair cable where necessary, ec. Finally, each eam is alloed a session o perform a demonsraion for he eacher. An example of final work of sudens during his laboraory course is shown in Fig. 5. r.p.m. sensor Condiioning circuis Daa ransmission Fig. 5. An example of sudens work. 3. RESULTS As in oher hands-on courses, suden moivaion and expecaion are grea. In fac, a low percenage of sudens op for a radiional laboraory course (i is also offered o sudens). Paricular cauion mus be shown in order o avoid an excessive workload, he mos ypical complain levelled
Proceedings, XVII IMEKO World Congress, June 22 27, 2003, Dubrovnik, Croaia by sudens on his kind of course. This is he main reason because boh, he prined circui boards and he objecs necessary o program he compuer are given o he sudens. Neverheless, he course, however, sill allows sudens o make heir own decisions since hey mus propose specificaions and design depends on hem. The cos of he course can be considered reasonable. The more expensive componens, such as he acceleromeers, he RTDs, he f/v converers or he microconrollers, as hey are plugged ino sockes, and hey can be re-used in laer courses. The only componens ha need be replaced are resisors, capaciors, inerlocking and prined boards for he signal condiioning circuis. For he firs year he course maerial cos is abou 240 /eam including he car. In subsequen years he cos is less han 75 /eam. 3.1 Oucomes of eacher observaion and experience The effor required on he par of he insrucors is considerable when compared o radiional courses, as hey increase he ineracion wih sudens. A meeing wih each eam, which is scheduled for each WP in order o: - Check progress. - Solve major sumbling blocks - Help sudens o work o a deadline So, he insrucor has and addiional work in relaion o radiional courses. However, he benefis are well worh he effor. The course allows sudens o acquire and consolidae mos imporan heoreical conceps from lecure classes, reinforced hrough experimenaion; i provides sudens wih a global view of Elecronic Insrumenaion and conribues o improving eacher-suden relaions. Fig. 6 shows he progress of he sudens during boh he Elecronic Insrumenaion heory-based course and he laboraory course in several opics covered in he syllabus. Progress in: Basic conceps Amplificaion & filering Sensors Conversion & ransmission Overall conceps Wors sudens Medium sudens Elecronic Insrumenaion course (lecure classes) Bes sudens WP 1 WP 2 WP 3 WP 4 WP 5 WP 6 Lecure Laboraory 3rd monh 6h monh 9h monh classes sar course sars Fig. 6. Suden progress during he course. To esimae he resuls of his laboraory course i is necessary o refer o he Fig. 6 and is consequences: i is easy o obain a good knowledge growh in good sudens and very difficul o reach similar resuls in wors sudens bu, wha is abou he medium suden? Usually, he medium suden obains medium resuls. In he laboraory course of Elecronic Insrumenaion in Oviedo Universiy, medium sudens can obain a knowledge level very close of bes sudens (Fig. 7). There are several causes for his improvemen: a) A high self-moivaion sae caused by he paricipaion in a complee projec (from he design o he es of prooype). b) Group work: bes suden in each eam can help oher eam members, inroducing a posiive feedback in he knowledge growh. c) Afer finishing each work package, he moivaion of sudens increases o face he nex WP. Laboraory course Tradiional course Iniial level 0% Unsaisfacory resuls Wors sudens Beer sudens Medium sudens Wors sudens % Beer sudens Medium sudens Improvemen Good resuls Bes suden level () Fig.7. Comparison beween he presened laboraory course and a radiional course in Elecronic Insrumenaion. Knowledge level improvemen is quie imporan for medium sudens. Sudens sae ha he course provided hem wih an undersanding of he concep of a complex insrumenaion sysem, and also esify o he course providing invaluable experience and know-how. The course encourages sudens o ge involved in oher courses run by he School of Engineering ha involve solving real world-ype problems. Mos of he eams complee all he asks saisfacorily. Typical failures are relaed o he design of he signal condiioning circuis and o inadequae wiring. Even so, he sudens sae ha hey learn much from heir misakes. Comparaive analysis hrough suden s performance in subsequen courses is difficul since his laboraory course is included in he final year of he six-year undergraduae course and less han 5% of graduae sudens go on o posgraduae level. However, some feedback is feasible rough he lecures who supervise graduaion projecs in elecronicrelaed areas: he ime required by he sudens o do his final projec (necessary o reach heir MSc.) has decreased bu also ha he qualiy of projecs has increased significanly since his laboraory course was inroduced. Excellen resuls
Proceedings, XVII IMEKO World Congress, June 22 27, 2003, Dubrovnik, Croaia Lecures in projecs in oher fields profess o no having observed any such differences. 3.2 Oucomes of suden assessmen In June 2002 (he monh when he laboraory course finishes) he 25 sudens following he laboraory course described in his paper were asked o fill a quesionnaire o evaluae he resuls: a) Mos of he sudens hink ha he course has been useful for a beer undersanding of lecure classes. b) The majoriy of sudens hink ha he course was useful for oher subjecs, insofar as i conribued o overall academic growh. c) I is also ineresing ha sudens do no consider he workload excessive; indeed, mos of hem hink ha he course was less difficul han hey had imagined before i sared. However, hese conclusions from sudens could be oo subjecive and hey mus be aking ino accoun carefully due o he disored poin of view caused by he small ime gap beween he laboraory course and he quesionnaire. Bu, feedback from sudens afer heir graduaion, o laer, becomes oo difficul in mos of cases. 4. CONCLUSIONS This course provides suden involvemen in asks ha lead o usually successful, complee insrumenaion design, similar o a real case, including signal condiioning, acquisiion, signal ransmission and visualizaion. However he course is no so differen from a radiional one in several ways. I is made up of several asks, i is relaively closely linked o he conens of lecures classes, and alhough he workload is greaer han in a radiional lab course, i canno be nor was considered as excessive. The main difference is he iner-connecion beween he asks, which makes he course much more useful han a radiional one for a beer undersanding of lecure classes and for overall academic growh. Such conclusions have, in fac, been raified by he sudens hemselves. REFERENCES [1] K. Waanabe, Insrumenaion educaion in Japan: Despair and expecaion, IEEE Insrum. & Meas. Mag., vol 2, pp. 14-19, Mar. 1999. [2] R. A. Wie, Engineering educaion for es and measuremen designers, IEEE Insrum. & Meas. Mag., vol 2, pp. 11-13, Mar. 1999. [3] A. Barwicz and R. Morwski, Teaching measuring sysems beyond he year 2000, IEEE Insrum. & Meas. Mag., vol 2, pp. 20-27, Mar. 1999. [4] T. Laopoulos, Teaching insrumenaion and measuremen in he complex-sysems era IEEE Insrum. & Meas. Mag., vol 2, pp. 28-30, Mar. 1999. [5] J. L. Schmalzel, I&M educaion for he new millennium. A U.S. perspecive. IEEE Insrum. & Meas. Mag., vol 2, pp. 31-36, Mar. 1999. [6] R. Morawski, R. Pallas-Areny, E. Periu, M. Siegel, and Th. Laopoulos, Curren rends on eaching Insrumenaion and measuremen, in Proc. 16h IEEE Ins. Meas. Tech. Conf., 2000, pp. 1715-1726. [7] S. Ghosh, Inegraing design ino undergraduae honors heses in a compuer engineering program: An experimen, IEEE Trans. Educ., vol. 43, pp. 200-210, May 2000. [8] R.B. Hilbor, Team learning for engineering sudens, IEEE Trans. Educ., vol. 37, pp. 207-211, May 1994. [9] S. Horan, Using measuremens and sensors in a pre-college enrichmen program, in Proc. 18h IEEE Ins. Meas. Conf., 2001, pp. 1968-1971. [10] T.W. Mahews and R.R. Spencer, An auonomous race car design compeiion, IEEE Trans. Educ., vol. 44, p. 215, May 2001. Auhors: Juan Carlos Campo Rodríguez: Associae Professor in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182427, FAX: +34985182138 e-mail: campo@ae.uniovi.es. Miguel Ángel Pérez García: Associae Professor in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182072, FAX: +34985182138 e-mail: Miguel@ae.uniovi.es. Francisco Javier Ferrero Marín: Associae Professor in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182552, FAX: +34985182138 e-mail: ferrero@ae.uniovi.es. Manuela González Vega: Associae Professor in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182555, FAX: +34985182138 e-mail: manuela@ae.uniovi.es. Juan Carlos Viera Pérez: Lecurer in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182551, FAX: +34985182138 e-mail: viera@ae.uniovi.es. Cecilio Blanco Viejo: Associae Professor in he Deparmen of Elecrical, Elecronic, Compuers and Sysems Engineering of Oviedo Universiy. Campus de Viesques s/n 33204 Gijón (SPAIN). Phone: +34985182554, FAX: +34985182138 e-mail: cecilio@ae.uniovi.es.