- Email: [email protected]
Compulab—Computing for the physical sciences teaching laboratory
03&l-1315/86 $3.00+0.00
compu~ E&c. Vol. 10. No. 2. pp. 307-313, 1986 Printed in Great Britain
PergamonPress Ltd
COMPULAB-COMPUTING FOR THE PHYSICAL SCIENCES TEACHING LABORATORY MORFYDD G. EDWARDS* and BERNARD E. WELLER The Polytechnic of the South Bank, Borough Road, London SE1 OAA, England (Received
15 April 1985; revision received 12 August 1985)
Abstract-In this paper a general purpose microcomputer-based system is described which is designed to support small-scale experimentation in the student laboratory. It comprises a low-cost hardware interface and a general&d software user-interface. The software provides a user-driven scientific workbench tool for the collection, analysis, display and storage of experimental data. Although designed initially for the physical sciences, it also has application in the life sciences. The requirements for such a system are discussed, design criteria are established and examples are given of the application of the system to some simple experiments. Experiences in using the system with teachers and school and college students contributed significantly to the development and indicate some of the desirable features for such software. The benefits of the general-purpose computer-assisted approach to experimentation in the teaching laboratory are both financial and pedagogical. However, there is a need to revise methods of laboratory teaching if these benefits are to be realisable.
1. INTRODUCTION
In 1982 and 1983 the ILEA invited the Polytechnic of the South Bank to mount courses for science teachers on the interfacing of the Research Machines 3802 microcomputer to experiments in the physical sciences teaching laboratories. These events became a catalyst for the development of a prototype system to support student laboratory experiments, which is the subject of this paper. Education in the Physical Sciences has not so far been strongly supported in terms of computer-based products. Current developments in the use of computers in science teaching laboratories rely largely upon the efforts of a few dedicated teachers. These are the individuals who have been prepared to acquire the knowledge and skills needed to set up the appropriate hardware and software. Most of this activity is, in consequence, centred on dedicated applications, with only enough facilities and documentation to meet locally defined needs. This contrasts with the use of commercially available, highly sophisticated and generalised systems such as those based on Wordstar, VisiCalc and dBaseI1, which can be used with little detailed knowledge of computers. What seems to be required is an equivalent, systems approach to science teaching laboratory work, leading to a realisation of the full potential of the technology. We believe that a particularly productive area for the attention of the science teacher is that of laboratory data logging and analysis. It has immediate benefits of removing the need for tedious manual data collection and mathematical manipulation. However, the introduction of powerful new tools to the learning situation always necessitates a review of teaching methods and materials. As we will illustrate below, this is particularly the case with the system which we have developed. It is also important to note that the Compulab development allows science teaching laboratories to mirror the changes which have taken and are taking place in industrial laboratories. In this paper, examples of use of the system will be given. Experiences in trials with users will be discussed and some implications for science teaching presented. Firstly, however, the basis for its design is described. 2. WHAT THE MICROCOMPUTER TO THE SCIENCE TEACHING
HAS TO OFFER LABORATORY
The laboratory workers, whether student or professional scientist, is concerned with the experimentation. Data has to be collected in an appropriate manner and form. It has then to be *Present address: The Centre for Computer Studies, Ngee Ann Polytechnic, 535 Clementi Road, Singapore 2159. 307
308
MORFYUD G. EDWARDS
and
BERNARD E. WELLER
mathematically manipulated and displayed in order to translate it into information about the phenomenon under study. The attributes of a microcomputer of speed, reliability, flexibility, information storage and graphics, combined with low cost and portability, find many applications in these activities [ 1.21. Using appropriate signal conditioning and interfacing equipment, data can be collected from most forms of transducer or instrument. Under software control the exact method and sequence of sampling can be implemented. We shall refer to this as the data collection protocol. There are obvious advantages to automatic data collection by computer in experiments which require rapid or time sensitive sampling, such as in kinetics of moving bodies or chemical reactions. Even if this is not the case, it is still advantageous to collect the data by computer in order to have it stored in a form which can be readily manipulated, displayed and recorded. The computational and graphics capabilities of the microcomputer can be put to use in providing rapid graphical displays of raw and processed data. The ability to see the data as it is being collected, in graphical form on the computer monitor, enables the experimenter to make informed judgements on data validity and quality, and conjecture on the development of the information contained in it. Similarly, automatic mathematical manipulation and display, carried out immediately after data collection, can save much of the tedium normally experienced in the postexperiment phase of the work and will encourage a more exploratory attitude towards data analysis. Storage of the data on disc means that analysis can take place whenever the experimenter chooses. This facility also enables the results of one experiment to be used in association with those of a later one, for calibration or comparative purposes. A further possibility, of particular interest to the science teacher, is that real experimental results can be displayed in front of the class to demonstrate phenomena under study, and illustrate their analysis. Such a teaching aid is preferable to some of the currently popular science simulation packages. The technology of small printers continues to improve at the same time as cost is being reduced. Many printers currently on the market can provide not only tabular hard copy of experimental results but also display screen images of, for instance, graph plots, both being essential components of the final written report of the experiment. We can choose to make all these attributes of a modern microcomputer system available through the development of appropriate software. Several well written packages are on the market which use some of the above ideas in support of particular families of experiments. However, the cost of equipping a complete laboratory with dedicated packages can be very high, both financially and in terms of user training and the provision of specialist interfacing. The team at the Polytechnic of the South Bank have chosen instead to take the general purpose approach, and this is thought to be particularly important to schools, where equipment purchasing is constrained by low budgets. The system under development there is designed to support experimentation in general, both in terms of hardware and software. Somewhat similar concepts underly the work of Illingworth[3]. 3. THE
BASIC
COMPULAB
SYSTEM
The system that we have developed comprises a low-cost interface unit and the software which drives it, together with a flexible, interactive applications package. It has since been adapted for use with several popular microcomputers. Although still in prototype form it is proving to be a valuable vehicle for investigations into the interactive uses of computers in science. The hardware interface allows both the monitoring and control of experiments. For monitoring, there are eight inputs, taking d.c. signals of up to 2.5 volts and providing digital output in 7 bit form. The same inputs can be employed with digital signals. For control, there are two analogue outputs and seven digital outputs. The whole is provided on a specially designed printed circuit board enclosed in a case with jack plug sockets. An on-board clock may be switched in to replace one of the signal inputs. The maximum sampling rate that can be achieved is about 100 Hz, which is adequate for the large majority of teaching experiments. The applications package is fully interactive, allowing the user to specify the data collection method and the analysis procedures to be used. Data is displayed in graphical form on the computer monitor both during collection and when subsequently required. Hard copy of raw and
Compulab
309
derived data can be obtained in tabular or graphical form on a suitable printer, and all results may be stored on disc and retrieved for later analysis. All these functions are available for use in any sensible order through simple screen menu control. In the prototype version the applications oackage provides only monitoring facilities. Experimental control will feature in subsequent versions. The localisation of the main functions within the software rather than the interface makes Compulab highly flexible in comparison with some of the systems available to schools, such as VELA in the U.K. 4.
THE
CRITERIA
FOR
SYSTEM
DESIGN
The design of an interactive system is, of necessity, an iterative process, with specification, implementation and user acceptance trials taking place in a step-wise and interleaved fashion. This is because user needs cannot be entirely predicted in advance, and perhaps should not be attempted. Such thinking is in line with the growing importance being attached to the design method called “prototyping”[4], in which the preliminary versions of a system are used as tools to refine the design. This approach proved to be particularly important in the work described here because potential users had difficulty in conceptualising the possibilities in the absence of a live demonstration, having never had experience with similar uses of the microcomputer in their work. An initial system was developed using extrapolation from experiences in the business and engineering design areas of computing plus the knowledge and skills of the members of the team, as scientists and teachers. The design was such as to allow rapid modification. The experiences of teachers with the resulting prototype have been encouraging, revealing its considerable potential. The need for the following supporting areas of study was revealed in the design phase of the work: 4.1 study of the method of experimental science, 4.2 study of the behaviour of the experimenter, 4.3 analysis of change when using the system. If the system is to be truly general-purpose then it must reflect the essence of the experimental method, representing the range and the commonality within most of the experiments used in the teaching laboratory. A preliminary study to augment the literature in this area has taken place, and a more extensive one is in progress. In his excellent critique of scientific method, Checkland [5] points out that central to the idea of experimentation is the concept of reductionism. One sense in which this is taken is that of reducing the complexity of the physical system under study to intellectually manageable proportions. In practice, one obvious illustration is that all but two variables in the system are held constant in order for their interdependence to be studied. If the resulting pattern of interdependence can be manipulated into a straight line, then the pattern is easily understood by the experimenter. Statistical methods are particularly well developed to allow us to exploit this situation and assess the reliability of our results, the most noteable vehicle being the least squares analysis method. For these reasons, a major feature of the prototype system is that it constrains the number of variables to be simultaneously analysed to two in number, although multiplexing on the eight inputs to the interface increases the range of variables that can be simultaneously monitored. Analysis of commonly used experiments showed that most could be handled in terms of three data collection protocols, involving sampling at regular intervals of time, or synchronised to externally derived pulses, or when indicated by the experimenter. The user is able to specify which one of these is required. Timing is provided by an on-board clock in specified multiples of its pulse rate. For synchronised sampling the clock may be switched out and its input channel connected to the appropriate signal source. For manual control the experimenter uses the space-bar on the keyboard to indicate that a sample should be taken. For time insensitive experiments the user may choose to input one or both the variables via the keyboard. During data collection the samples are reported both as displayed digital values and as points on a graph. Should the data be seen to be unreliable, then the process may be aborted with or without retention of the data collected up to that point. Data may be calibrated with previously stored values. The analysis facilities provided in the prototype reflect those most commonly required for linear or simple curve data relationships, including algebraic, trigonometric and
310
MORFYDD G. EDWARDS and BERNARDE. WELLER
logarithmic operations. In future versions it is intended to include further facilities such as interpolation, area under a specific region of the plot and first derivative. Finally, since true experimentation often requires an iterative approach, all the above facilities are available for selection in any sensible order, rapidly, and without need for user programming. A second area of study, concentrating on the behaviour and terminology of the student and the professional experimenter, is required in order to design a user-machine interface which is acceptable and easy to use. It was also the aim of the authors to ensure that the attentions and labours of the user were not directed away from the experimental process towards the mechanics of the computer and its specialist body of knowledge. Program control is provided in the form of screen templates and menus which give the benefits of clarity and rapid activation of functions. Since only those options which are currently in context can be accessed from a menu, the probability of erroneous input is greatly reduced. At all times, variables are referenced by their scientific names and values are expressed in physical units. Considerable attention is given to providing graph plots which obey the conventions of scientific representation in terms of scaling, the use of the origin and variable dimensions. The number of digits of precision in which values are reported are constrained realistically, and, where possible, mathematical notation follows scientific rather than computing practice e.g. scientific notation for numbers and In for the logarithmic function rather than log. Finally, recognising the fact that the introduction of computers always brings about some change in the behaviour of the users, a sensitive appraisal of the anticipated effects on teachers and students is required, together with observations of the system in use. There are obvious benefits in cost and time if the microcomputer can be successfully employed in the laboratory. Further, if the facilities outlined above can be provided in an acceptable form then there will be increased opportunities for the student to explore the methods of experimentation and data analysis. However, this will require some redesign of teaching experiments, and a willingness on the part of the teacher to re-evaluate the objectives and procedures of laboratory teaching. Some consideration must also be given, as in the case of the pocket calculator, to the prevention of de-skilling with respect to laboratory based studies. Neither should it be forgotten that the interfacing of experiments to computers, even with such systems as the one described below, requires the skill to select and use available transducers, a new topic for many science teachers. As these factors call for further study the system was designed so as to enable easy modification of functions and the user interface.
5. EXAMPLES
OF USE OF THE
SYSTEM
To illustrate the capabilities of the system the procedures involved in a few simple experiments will be outlined. In the first, the capacitance of a capacitor, Cl, is to be determined by comparing its discharge rate with that of a standard, known capacitor, C2. Both capacitors are to be charged to the same voltage and discharged simultaneously through equivalent resistors. The slope of the graph of the logarithm of one voltage, In Vl, against the logarithm of the other, In V2, will yield the ratio of the capacitances and so allow Cl to be calculated. The experiment is set up with the voltages across each capacitor as separate inputs to the hardware interface. The software package is run and the user is first presented with a screen template which allows the following specification to be entered: 5.1 There are to be two variables, named Vl and V2, with unit range 0 to 2.5 volts and units “V” to be input on two specified interface inputs. 5.2 The data collection protocol is to be TIMED, using a sampling period of 0.5 seconds. 5.3 For immediate data plotting, clock time is to be the controlled variable. Secondly, the menu option SAMPLE is selected and the number of samples to be taken, say 40, is specified. Sampling commences when the user initiates the discharge, signalled to the computer by the pressing of the space-bar. (An alternative option is for the user to synchronise the start of sampling through the use of an electrical signal applied to another input of the interface.)
Compulab
311
Following successful data collection, which has been monitored via the simultaneous screen plot and display of collected signal values, the user selects the menu option ANALYSE. Via further menus the appropriate mathematical functions are applied to the raw data values, using auxiliary value arrays named x and y. In this case the functions will be x = In VI and y = In V2 and the system will set and record the dimensions as null. To reveal the result of the manipulation the menu option VIEW is selected, which gives access to screen and printer plotting of graphed or tabular data. Screen plotting of y versus x is selected and the results viewed. The range of values which are considered to be reliable, e.g. not suffering from excessive loss of precision at the lower end, is specified as the range over which least squares fit is required, and the best fit line, slope and intercept are displayed. Finally, the menu option SAVE is selected to store the experimental results on disc, and the option VIEW is again selected, this time to obtain printed output of graphs and numeric values. All this will have taken no more than five minutes. As a second experiment we take the investigation of the variation of the pH of a solution with concentration of solute. In this case the variables are to be concentration, to be input numerically via the keyboard, and the e.m.f. across a pair of electrodes submerged in the liquid, to be monitored by the interface. A sequence of data points is to be obtained by dipping the electrodes in turn in a number of beakers containing different concentrations of solute. A plot of amplified e.m.f. against concentration is expected to be exponential in form, with a straight line resulting from taking the logarithm of the concentration. The overall procedure is similar to that described for the capacitor discharge experiment, the major difference being in the selection of the data collection protocol. Here, time sampling is not required. The experimenter has to change the solution prior to each sample, and so elects for MANUAL control of sampling times. The set of numeric values of the concentration may be input before sampling commences or individual values can be supplied at sample points. The plot of raw data will be of e.m.f. against con~ntration, with the latter as the controlled variable. The third example is the falling sphere viscometer. The viscosity of a fluid is to be determined by measuring the terminal velocities of metal balls of varying sizes as they fall freely in a vertical tube of the fluid. Two photocells and light sources are placed along the tube at the interval over which the fall of the spheres will be measured. The two variables involved here will be the time, t, of fall between the two photocells and the radius, r, of the sphere. A plot of t against the reciprocal of the square of r is expected to be a straight line with slope proportional to viscosity. The data collection protocol to be selected here is SYNCHRONISED. The variable r is to be input manually. Elapsed time, t, is to be provided via the interface. The suitably amplified outputs of the two photocells are connected to two inputs of the interface. As the sphere passes the first photocell time recording commences. As the sphere passes the second photocell the elapsed time is recorded and a point is plotted on the graph. This process is repeated for each sphere. Data analysis then proceeds as before. An interesting feature of this experiment is that the system can be used to establish the correct positioning of the photocells by a preliminary run essentially of the same form, but with the purpose of confirming that terminal velocities have been reached. Further, the described method of determining the velocities of the spheres is considerably more reliable than when using a stop-watch and visual observation. Other modes of SYNCHRONISED data collection are also available. In all the above cases it is assumed that the experiment goes entirely to plan. In reality, there will be times when the raw data is unreliable because of scatter, drift, bias or lack of precision. If this occurs then it will be immediately obvious from the simultaneous screen plot, and remedial action can be taken. Data collection can be halted and repeated, or ceased prematurely with retention of data collected up to that point. At other times the unacceptability of the data may not be realised until the data analysis phase, but this can be carried out immediately after sampling, again allowing the experiment to be repeated during the same laboratory period. Although the system was primarily intended for the management of live experiments its data analysis and storage facilities have provided an interesting additional teaching medium. Using the option of keyboard data entry we have been able to set up sets of data derived from notable historical experiments. This enables a student to play the role of the original investigator in seeking to discover the underlying principles illustrated by the experimental results. One that has particular
312
MORFYDD G. EDWARDS and BERNARDE. WELLER
impact, being a cornerstone of Physical Science, is that of the experiments carried out by Robert Boyle on the properties of air in 1662. This approach allows students to discover the gas laws rather than to be passive recipients of these equations. There are many other examples of experiments that could be described as subjects of the Compulab system, but this is outside the scope of the present paper. The above have illustrated the versatility of the system in terms of data collection protocol, which is achieved without need for user programming or modification of the system. Other examples could be chosen to illustrate its value for experiments with very short or very long sampling periods, and for environmental monitoring during data collection. 6. EXPERIENCES
WITH
TEACHERS
The reactions of users during the development of the prototype have been essential in tuning the system and in increasing its versatility and usefulness. Detailed studies of the employment of Compulab in teaching laboratories are planned. The teachers who were participants of the ILEA course mentioned above greeted the system with enthusiasm and confirmed that the design met its objectives in terms of ease of use and appropriateness. There were several calls for additional facilities and it is of interest that these were mainly directed at increasing the visibility of the system functions. Examples of features which resulted from these suggestions are: 6.1 6.2 6.3 6.4
The display of numerical data values alongside the plotted graph during data collection. An option to review the details of the experimental configuration. An option to review the equations applied to the raw data. An option to display tabulated numeric values on the screen after data collection or analysis.
Although all the requests were considered to be valid ones[lO] it remains to be investigated why visibility appears to be so important to the user. It may be that the presence of the computer between the teacher and the experiment creates a feeling of insecurity, which is lessened if its functions are more obvious. Alternatively, it may be that concentration and creative thinking are aided by the knowledge that all the available information, even if redundant, is readily accessible. If this phenomenon occurs with teacher users, then it is likely to be even more apparent with students, and more investigations in this area are needed to support future developments of the system. Of more concern to the authors was the reluctance with which some of the teachers explored the uses of the system outside the most simple experiments. The powerful facilities available were obviously posing a challenge to them to review their whole approach to laboratory work. This is understandable, as traditional teaching experiments are tried and tested and well understood, even though they are heavily prescribed by cost and the limitations of manual methods. Yet there are obvious advantages in the introduction of computing aids to science teaching in that it allows us to provide a learning environment that reflects modern laboratory practice. Although the general-purpose nature of Compulab, in comparison with dedicated packages or instruments, poses burdens on the interpreter, it represents one of the few possibilities open to us to escape from the limitations of low educational spending. The obvious solution is for the teaching profession as a whole to respond to the challenge, by providing revised laboratory exercises and in-service training courses on computers in the laboratory. At the Polytechnic some of this work is currently under way. 7. CONCLUSIONS The development of the Compulab system has confirmed that a valid general-purpose approach to the use of the computer in science teaching laboratories is possible. The original aims of introducing automated, rapid and visual data collection and analysis has been realised for a major part of the science cirriculum. It is hoped to make versions of the system commercially available in the near future. The introduction of such a system has far reaching implications. Principal amongst these are:
Compulab
313
7.1 There exists the possibility to introduce modern computing aids to student laboratory work. This can be realised at low cost not only in financial terms but also in relation to user training. 7.2 There is the chance to make Science more exciting for the student by eliminating much time consuming and tedious data collection and analysis. 7.3 The system highlights the principles underlying the experimental method by enhancing the visibility of the experiment at all stages. 7.4 The versatility of the system allows a more flexible approach to the design of student laboratory experiments, both in terms of data collection and analysis, and in the role to be played by the student. 7.5 Records of historical experiments now become readily accessible and allow students the facility to examine and analyse such data. 7.6 Trends in the use of computers in industrial laboratories can be reflected in science teaching. 7.7 Initial and in-service teacher training facilities should reflect the pedagogical implications of such computer-based educational aids. 7.8 Above all there is a need for a major revision in the methods of laboratory teaching in line with the uses of computers, and in the provision of associated teaching materials. The techniques developed for education can be extended to the low-cost end of professional laboratory work. This area of development is just one of many that are currently arousing interest, examples being scientific data bases[6], scientific word processing[7] and the concept of the automated laboratory[8,9]. Once all these developments are under way one can point to an interesting future for the experimenter, whether student or professional scientist. Acknowledgemenrs-The authors gratefully acknowledge the invaluable efforts of the other members of the project team, notably Malcolm Maclenan for designing the interface, and Howard Main for contributing to the software development.
REFERENCES 1. Weller B. E., Micromania in chemistry. Chem. Br. 20, 526 (1984);Lab. Microcompur. 17, I (1982). , 2. James E. B., Chem. Br. 18, 620 (1982). 3. Illingworth R., Microcomputer assisted physics experiments. Eur. J. Phys. 201-204 (1984). 4. Wasserman A. J. and Gutz S., The future of programming. Commun. ACM 25, 3 (1982). 5. Checkland P., Systems Thinking, Sysrems P&I&. Wiley, Chichester (198 I). 6. Shoshani A.. Olken F. and Wona H. K. T.. Characteristics of scientific data bases. ProceediwsI ofI rhe f&h Inrernarionul Conference on Very Large Data-Bases, Singapore (1984). 7. Johnston M. G., Scientific word processing using Applewriter II. Lob. Microcompur. 79, 3 (1984). 8. Broadbridge R., Interfacing microcomputers-practical exercises. Lob. Microcomput. 8, 2 (1983). 9. Malcolm-Lawes D. J., Microcomputers in the chemical laboratory. Lab. Microcompur. 16, 2 (1983); Microcomputers and Luborarory Instrumentation. Plenum Press, New York (1984). IO. Schneiderman B.. Human factors experiments in designing interactive systems. Computer (December 1979).
C.A.E.
IO,&E
compu~ E&c. Vol. 10. No. 2. pp. 307-313, 1986 Printed in Great Britain
PergamonPress Ltd
COMPULAB-COMPUTING FOR THE PHYSICAL SCIENCES TEACHING LABORATORY MORFYDD G. EDWARDS* and BERNARD E. WELLER The Polytechnic of the South Bank, Borough Road, London SE1 OAA, England (Received
15 April 1985; revision received 12 August 1985)
Abstract-In this paper a general purpose microcomputer-based system is described which is designed to support small-scale experimentation in the student laboratory. It comprises a low-cost hardware interface and a general&d software user-interface. The software provides a user-driven scientific workbench tool for the collection, analysis, display and storage of experimental data. Although designed initially for the physical sciences, it also has application in the life sciences. The requirements for such a system are discussed, design criteria are established and examples are given of the application of the system to some simple experiments. Experiences in using the system with teachers and school and college students contributed significantly to the development and indicate some of the desirable features for such software. The benefits of the general-purpose computer-assisted approach to experimentation in the teaching laboratory are both financial and pedagogical. However, there is a need to revise methods of laboratory teaching if these benefits are to be realisable.
1. INTRODUCTION
In 1982 and 1983 the ILEA invited the Polytechnic of the South Bank to mount courses for science teachers on the interfacing of the Research Machines 3802 microcomputer to experiments in the physical sciences teaching laboratories. These events became a catalyst for the development of a prototype system to support student laboratory experiments, which is the subject of this paper. Education in the Physical Sciences has not so far been strongly supported in terms of computer-based products. Current developments in the use of computers in science teaching laboratories rely largely upon the efforts of a few dedicated teachers. These are the individuals who have been prepared to acquire the knowledge and skills needed to set up the appropriate hardware and software. Most of this activity is, in consequence, centred on dedicated applications, with only enough facilities and documentation to meet locally defined needs. This contrasts with the use of commercially available, highly sophisticated and generalised systems such as those based on Wordstar, VisiCalc and dBaseI1, which can be used with little detailed knowledge of computers. What seems to be required is an equivalent, systems approach to science teaching laboratory work, leading to a realisation of the full potential of the technology. We believe that a particularly productive area for the attention of the science teacher is that of laboratory data logging and analysis. It has immediate benefits of removing the need for tedious manual data collection and mathematical manipulation. However, the introduction of powerful new tools to the learning situation always necessitates a review of teaching methods and materials. As we will illustrate below, this is particularly the case with the system which we have developed. It is also important to note that the Compulab development allows science teaching laboratories to mirror the changes which have taken and are taking place in industrial laboratories. In this paper, examples of use of the system will be given. Experiences in trials with users will be discussed and some implications for science teaching presented. Firstly, however, the basis for its design is described. 2. WHAT THE MICROCOMPUTER TO THE SCIENCE TEACHING
HAS TO OFFER LABORATORY
The laboratory workers, whether student or professional scientist, is concerned with the experimentation. Data has to be collected in an appropriate manner and form. It has then to be *Present address: The Centre for Computer Studies, Ngee Ann Polytechnic, 535 Clementi Road, Singapore 2159. 307
308
MORFYUD G. EDWARDS
and
BERNARD E. WELLER
mathematically manipulated and displayed in order to translate it into information about the phenomenon under study. The attributes of a microcomputer of speed, reliability, flexibility, information storage and graphics, combined with low cost and portability, find many applications in these activities [ 1.21. Using appropriate signal conditioning and interfacing equipment, data can be collected from most forms of transducer or instrument. Under software control the exact method and sequence of sampling can be implemented. We shall refer to this as the data collection protocol. There are obvious advantages to automatic data collection by computer in experiments which require rapid or time sensitive sampling, such as in kinetics of moving bodies or chemical reactions. Even if this is not the case, it is still advantageous to collect the data by computer in order to have it stored in a form which can be readily manipulated, displayed and recorded. The computational and graphics capabilities of the microcomputer can be put to use in providing rapid graphical displays of raw and processed data. The ability to see the data as it is being collected, in graphical form on the computer monitor, enables the experimenter to make informed judgements on data validity and quality, and conjecture on the development of the information contained in it. Similarly, automatic mathematical manipulation and display, carried out immediately after data collection, can save much of the tedium normally experienced in the postexperiment phase of the work and will encourage a more exploratory attitude towards data analysis. Storage of the data on disc means that analysis can take place whenever the experimenter chooses. This facility also enables the results of one experiment to be used in association with those of a later one, for calibration or comparative purposes. A further possibility, of particular interest to the science teacher, is that real experimental results can be displayed in front of the class to demonstrate phenomena under study, and illustrate their analysis. Such a teaching aid is preferable to some of the currently popular science simulation packages. The technology of small printers continues to improve at the same time as cost is being reduced. Many printers currently on the market can provide not only tabular hard copy of experimental results but also display screen images of, for instance, graph plots, both being essential components of the final written report of the experiment. We can choose to make all these attributes of a modern microcomputer system available through the development of appropriate software. Several well written packages are on the market which use some of the above ideas in support of particular families of experiments. However, the cost of equipping a complete laboratory with dedicated packages can be very high, both financially and in terms of user training and the provision of specialist interfacing. The team at the Polytechnic of the South Bank have chosen instead to take the general purpose approach, and this is thought to be particularly important to schools, where equipment purchasing is constrained by low budgets. The system under development there is designed to support experimentation in general, both in terms of hardware and software. Somewhat similar concepts underly the work of Illingworth[3]. 3. THE
BASIC
COMPULAB
SYSTEM
The system that we have developed comprises a low-cost interface unit and the software which drives it, together with a flexible, interactive applications package. It has since been adapted for use with several popular microcomputers. Although still in prototype form it is proving to be a valuable vehicle for investigations into the interactive uses of computers in science. The hardware interface allows both the monitoring and control of experiments. For monitoring, there are eight inputs, taking d.c. signals of up to 2.5 volts and providing digital output in 7 bit form. The same inputs can be employed with digital signals. For control, there are two analogue outputs and seven digital outputs. The whole is provided on a specially designed printed circuit board enclosed in a case with jack plug sockets. An on-board clock may be switched in to replace one of the signal inputs. The maximum sampling rate that can be achieved is about 100 Hz, which is adequate for the large majority of teaching experiments. The applications package is fully interactive, allowing the user to specify the data collection method and the analysis procedures to be used. Data is displayed in graphical form on the computer monitor both during collection and when subsequently required. Hard copy of raw and
Compulab
309
derived data can be obtained in tabular or graphical form on a suitable printer, and all results may be stored on disc and retrieved for later analysis. All these functions are available for use in any sensible order through simple screen menu control. In the prototype version the applications oackage provides only monitoring facilities. Experimental control will feature in subsequent versions. The localisation of the main functions within the software rather than the interface makes Compulab highly flexible in comparison with some of the systems available to schools, such as VELA in the U.K. 4.
THE
CRITERIA
FOR
SYSTEM
DESIGN
The design of an interactive system is, of necessity, an iterative process, with specification, implementation and user acceptance trials taking place in a step-wise and interleaved fashion. This is because user needs cannot be entirely predicted in advance, and perhaps should not be attempted. Such thinking is in line with the growing importance being attached to the design method called “prototyping”[4], in which the preliminary versions of a system are used as tools to refine the design. This approach proved to be particularly important in the work described here because potential users had difficulty in conceptualising the possibilities in the absence of a live demonstration, having never had experience with similar uses of the microcomputer in their work. An initial system was developed using extrapolation from experiences in the business and engineering design areas of computing plus the knowledge and skills of the members of the team, as scientists and teachers. The design was such as to allow rapid modification. The experiences of teachers with the resulting prototype have been encouraging, revealing its considerable potential. The need for the following supporting areas of study was revealed in the design phase of the work: 4.1 study of the method of experimental science, 4.2 study of the behaviour of the experimenter, 4.3 analysis of change when using the system. If the system is to be truly general-purpose then it must reflect the essence of the experimental method, representing the range and the commonality within most of the experiments used in the teaching laboratory. A preliminary study to augment the literature in this area has taken place, and a more extensive one is in progress. In his excellent critique of scientific method, Checkland [5] points out that central to the idea of experimentation is the concept of reductionism. One sense in which this is taken is that of reducing the complexity of the physical system under study to intellectually manageable proportions. In practice, one obvious illustration is that all but two variables in the system are held constant in order for their interdependence to be studied. If the resulting pattern of interdependence can be manipulated into a straight line, then the pattern is easily understood by the experimenter. Statistical methods are particularly well developed to allow us to exploit this situation and assess the reliability of our results, the most noteable vehicle being the least squares analysis method. For these reasons, a major feature of the prototype system is that it constrains the number of variables to be simultaneously analysed to two in number, although multiplexing on the eight inputs to the interface increases the range of variables that can be simultaneously monitored. Analysis of commonly used experiments showed that most could be handled in terms of three data collection protocols, involving sampling at regular intervals of time, or synchronised to externally derived pulses, or when indicated by the experimenter. The user is able to specify which one of these is required. Timing is provided by an on-board clock in specified multiples of its pulse rate. For synchronised sampling the clock may be switched out and its input channel connected to the appropriate signal source. For manual control the experimenter uses the space-bar on the keyboard to indicate that a sample should be taken. For time insensitive experiments the user may choose to input one or both the variables via the keyboard. During data collection the samples are reported both as displayed digital values and as points on a graph. Should the data be seen to be unreliable, then the process may be aborted with or without retention of the data collected up to that point. Data may be calibrated with previously stored values. The analysis facilities provided in the prototype reflect those most commonly required for linear or simple curve data relationships, including algebraic, trigonometric and
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logarithmic operations. In future versions it is intended to include further facilities such as interpolation, area under a specific region of the plot and first derivative. Finally, since true experimentation often requires an iterative approach, all the above facilities are available for selection in any sensible order, rapidly, and without need for user programming. A second area of study, concentrating on the behaviour and terminology of the student and the professional experimenter, is required in order to design a user-machine interface which is acceptable and easy to use. It was also the aim of the authors to ensure that the attentions and labours of the user were not directed away from the experimental process towards the mechanics of the computer and its specialist body of knowledge. Program control is provided in the form of screen templates and menus which give the benefits of clarity and rapid activation of functions. Since only those options which are currently in context can be accessed from a menu, the probability of erroneous input is greatly reduced. At all times, variables are referenced by their scientific names and values are expressed in physical units. Considerable attention is given to providing graph plots which obey the conventions of scientific representation in terms of scaling, the use of the origin and variable dimensions. The number of digits of precision in which values are reported are constrained realistically, and, where possible, mathematical notation follows scientific rather than computing practice e.g. scientific notation for numbers and In for the logarithmic function rather than log. Finally, recognising the fact that the introduction of computers always brings about some change in the behaviour of the users, a sensitive appraisal of the anticipated effects on teachers and students is required, together with observations of the system in use. There are obvious benefits in cost and time if the microcomputer can be successfully employed in the laboratory. Further, if the facilities outlined above can be provided in an acceptable form then there will be increased opportunities for the student to explore the methods of experimentation and data analysis. However, this will require some redesign of teaching experiments, and a willingness on the part of the teacher to re-evaluate the objectives and procedures of laboratory teaching. Some consideration must also be given, as in the case of the pocket calculator, to the prevention of de-skilling with respect to laboratory based studies. Neither should it be forgotten that the interfacing of experiments to computers, even with such systems as the one described below, requires the skill to select and use available transducers, a new topic for many science teachers. As these factors call for further study the system was designed so as to enable easy modification of functions and the user interface.
5. EXAMPLES
OF USE OF THE
SYSTEM
To illustrate the capabilities of the system the procedures involved in a few simple experiments will be outlined. In the first, the capacitance of a capacitor, Cl, is to be determined by comparing its discharge rate with that of a standard, known capacitor, C2. Both capacitors are to be charged to the same voltage and discharged simultaneously through equivalent resistors. The slope of the graph of the logarithm of one voltage, In Vl, against the logarithm of the other, In V2, will yield the ratio of the capacitances and so allow Cl to be calculated. The experiment is set up with the voltages across each capacitor as separate inputs to the hardware interface. The software package is run and the user is first presented with a screen template which allows the following specification to be entered: 5.1 There are to be two variables, named Vl and V2, with unit range 0 to 2.5 volts and units “V” to be input on two specified interface inputs. 5.2 The data collection protocol is to be TIMED, using a sampling period of 0.5 seconds. 5.3 For immediate data plotting, clock time is to be the controlled variable. Secondly, the menu option SAMPLE is selected and the number of samples to be taken, say 40, is specified. Sampling commences when the user initiates the discharge, signalled to the computer by the pressing of the space-bar. (An alternative option is for the user to synchronise the start of sampling through the use of an electrical signal applied to another input of the interface.)
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Following successful data collection, which has been monitored via the simultaneous screen plot and display of collected signal values, the user selects the menu option ANALYSE. Via further menus the appropriate mathematical functions are applied to the raw data values, using auxiliary value arrays named x and y. In this case the functions will be x = In VI and y = In V2 and the system will set and record the dimensions as null. To reveal the result of the manipulation the menu option VIEW is selected, which gives access to screen and printer plotting of graphed or tabular data. Screen plotting of y versus x is selected and the results viewed. The range of values which are considered to be reliable, e.g. not suffering from excessive loss of precision at the lower end, is specified as the range over which least squares fit is required, and the best fit line, slope and intercept are displayed. Finally, the menu option SAVE is selected to store the experimental results on disc, and the option VIEW is again selected, this time to obtain printed output of graphs and numeric values. All this will have taken no more than five minutes. As a second experiment we take the investigation of the variation of the pH of a solution with concentration of solute. In this case the variables are to be concentration, to be input numerically via the keyboard, and the e.m.f. across a pair of electrodes submerged in the liquid, to be monitored by the interface. A sequence of data points is to be obtained by dipping the electrodes in turn in a number of beakers containing different concentrations of solute. A plot of amplified e.m.f. against concentration is expected to be exponential in form, with a straight line resulting from taking the logarithm of the concentration. The overall procedure is similar to that described for the capacitor discharge experiment, the major difference being in the selection of the data collection protocol. Here, time sampling is not required. The experimenter has to change the solution prior to each sample, and so elects for MANUAL control of sampling times. The set of numeric values of the concentration may be input before sampling commences or individual values can be supplied at sample points. The plot of raw data will be of e.m.f. against con~ntration, with the latter as the controlled variable. The third example is the falling sphere viscometer. The viscosity of a fluid is to be determined by measuring the terminal velocities of metal balls of varying sizes as they fall freely in a vertical tube of the fluid. Two photocells and light sources are placed along the tube at the interval over which the fall of the spheres will be measured. The two variables involved here will be the time, t, of fall between the two photocells and the radius, r, of the sphere. A plot of t against the reciprocal of the square of r is expected to be a straight line with slope proportional to viscosity. The data collection protocol to be selected here is SYNCHRONISED. The variable r is to be input manually. Elapsed time, t, is to be provided via the interface. The suitably amplified outputs of the two photocells are connected to two inputs of the interface. As the sphere passes the first photocell time recording commences. As the sphere passes the second photocell the elapsed time is recorded and a point is plotted on the graph. This process is repeated for each sphere. Data analysis then proceeds as before. An interesting feature of this experiment is that the system can be used to establish the correct positioning of the photocells by a preliminary run essentially of the same form, but with the purpose of confirming that terminal velocities have been reached. Further, the described method of determining the velocities of the spheres is considerably more reliable than when using a stop-watch and visual observation. Other modes of SYNCHRONISED data collection are also available. In all the above cases it is assumed that the experiment goes entirely to plan. In reality, there will be times when the raw data is unreliable because of scatter, drift, bias or lack of precision. If this occurs then it will be immediately obvious from the simultaneous screen plot, and remedial action can be taken. Data collection can be halted and repeated, or ceased prematurely with retention of data collected up to that point. At other times the unacceptability of the data may not be realised until the data analysis phase, but this can be carried out immediately after sampling, again allowing the experiment to be repeated during the same laboratory period. Although the system was primarily intended for the management of live experiments its data analysis and storage facilities have provided an interesting additional teaching medium. Using the option of keyboard data entry we have been able to set up sets of data derived from notable historical experiments. This enables a student to play the role of the original investigator in seeking to discover the underlying principles illustrated by the experimental results. One that has particular
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impact, being a cornerstone of Physical Science, is that of the experiments carried out by Robert Boyle on the properties of air in 1662. This approach allows students to discover the gas laws rather than to be passive recipients of these equations. There are many other examples of experiments that could be described as subjects of the Compulab system, but this is outside the scope of the present paper. The above have illustrated the versatility of the system in terms of data collection protocol, which is achieved without need for user programming or modification of the system. Other examples could be chosen to illustrate its value for experiments with very short or very long sampling periods, and for environmental monitoring during data collection. 6. EXPERIENCES
WITH
TEACHERS
The reactions of users during the development of the prototype have been essential in tuning the system and in increasing its versatility and usefulness. Detailed studies of the employment of Compulab in teaching laboratories are planned. The teachers who were participants of the ILEA course mentioned above greeted the system with enthusiasm and confirmed that the design met its objectives in terms of ease of use and appropriateness. There were several calls for additional facilities and it is of interest that these were mainly directed at increasing the visibility of the system functions. Examples of features which resulted from these suggestions are: 6.1 6.2 6.3 6.4
The display of numerical data values alongside the plotted graph during data collection. An option to review the details of the experimental configuration. An option to review the equations applied to the raw data. An option to display tabulated numeric values on the screen after data collection or analysis.
Although all the requests were considered to be valid ones[lO] it remains to be investigated why visibility appears to be so important to the user. It may be that the presence of the computer between the teacher and the experiment creates a feeling of insecurity, which is lessened if its functions are more obvious. Alternatively, it may be that concentration and creative thinking are aided by the knowledge that all the available information, even if redundant, is readily accessible. If this phenomenon occurs with teacher users, then it is likely to be even more apparent with students, and more investigations in this area are needed to support future developments of the system. Of more concern to the authors was the reluctance with which some of the teachers explored the uses of the system outside the most simple experiments. The powerful facilities available were obviously posing a challenge to them to review their whole approach to laboratory work. This is understandable, as traditional teaching experiments are tried and tested and well understood, even though they are heavily prescribed by cost and the limitations of manual methods. Yet there are obvious advantages in the introduction of computing aids to science teaching in that it allows us to provide a learning environment that reflects modern laboratory practice. Although the general-purpose nature of Compulab, in comparison with dedicated packages or instruments, poses burdens on the interpreter, it represents one of the few possibilities open to us to escape from the limitations of low educational spending. The obvious solution is for the teaching profession as a whole to respond to the challenge, by providing revised laboratory exercises and in-service training courses on computers in the laboratory. At the Polytechnic some of this work is currently under way. 7. CONCLUSIONS The development of the Compulab system has confirmed that a valid general-purpose approach to the use of the computer in science teaching laboratories is possible. The original aims of introducing automated, rapid and visual data collection and analysis has been realised for a major part of the science cirriculum. It is hoped to make versions of the system commercially available in the near future. The introduction of such a system has far reaching implications. Principal amongst these are:
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7.1 There exists the possibility to introduce modern computing aids to student laboratory work. This can be realised at low cost not only in financial terms but also in relation to user training. 7.2 There is the chance to make Science more exciting for the student by eliminating much time consuming and tedious data collection and analysis. 7.3 The system highlights the principles underlying the experimental method by enhancing the visibility of the experiment at all stages. 7.4 The versatility of the system allows a more flexible approach to the design of student laboratory experiments, both in terms of data collection and analysis, and in the role to be played by the student. 7.5 Records of historical experiments now become readily accessible and allow students the facility to examine and analyse such data. 7.6 Trends in the use of computers in industrial laboratories can be reflected in science teaching. 7.7 Initial and in-service teacher training facilities should reflect the pedagogical implications of such computer-based educational aids. 7.8 Above all there is a need for a major revision in the methods of laboratory teaching in line with the uses of computers, and in the provision of associated teaching materials. The techniques developed for education can be extended to the low-cost end of professional laboratory work. This area of development is just one of many that are currently arousing interest, examples being scientific data bases[6], scientific word processing[7] and the concept of the automated laboratory[8,9]. Once all these developments are under way one can point to an interesting future for the experimenter, whether student or professional scientist. Acknowledgemenrs-The authors gratefully acknowledge the invaluable efforts of the other members of the project team, notably Malcolm Maclenan for designing the interface, and Howard Main for contributing to the software development.
REFERENCES 1. Weller B. E., Micromania in chemistry. Chem. Br. 20, 526 (1984);Lab. Microcompur. 17, I (1982). , 2. James E. B., Chem. Br. 18, 620 (1982). 3. Illingworth R., Microcomputer assisted physics experiments. Eur. J. Phys. 201-204 (1984). 4. Wasserman A. J. and Gutz S., The future of programming. Commun. ACM 25, 3 (1982). 5. Checkland P., Systems Thinking, Sysrems P&I&. Wiley, Chichester (198 I). 6. Shoshani A.. Olken F. and Wona H. K. T.. Characteristics of scientific data bases. ProceediwsI ofI rhe f&h Inrernarionul Conference on Very Large Data-Bases, Singapore (1984). 7. Johnston M. G., Scientific word processing using Applewriter II. Lob. Microcompur. 79, 3 (1984). 8. Broadbridge R., Interfacing microcomputers-practical exercises. Lob. Microcomput. 8, 2 (1983). 9. Malcolm-Lawes D. J., Microcomputers in the chemical laboratory. Lab. Microcompur. 16, 2 (1983); Microcomputers and Luborarory Instrumentation. Plenum Press, New York (1984). IO. Schneiderman B.. Human factors experiments in designing interactive systems. Computer (December 1979).
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