Draft: SmartProbes Concept Paper
Robert Tinker and Stephen Bannasch
The Concord Consortium, http://www.concord.org/

	Abstract

Good science and effective science learning are built on measuring the world around you, thinking hard about what the data mean, and describing what you discover to someone else. By integrating the measurement process with computing technology all three aspects of this process are greatly facilitated. Accurate measurements can be made very quickly or over a long time. Graphs constructed from the data can be placed into reports which are electronically copied and distributed. While there has a great deal of development of computing tools for analysis and communication we believe the development of probes and interfaces designed for education has lagged. Measurement inherently involves translation and interaction between physical and abstract worlds. The time, costs and complexities involved can make accurate measurement difficult. These difficulties contribute to an unfortunate trend where science education is removed not just from the everyday world around us but even from the science lab. By combining advances in low-cost sensors with inexpensive micro-controllers we can not only make probes cheaper but also make them more portable, easier to use and more accurate. We call this new measurement technology SmartProbes. By connecting these new SmartProbes to powerful software embedded in the new computing paradigm of computing and communication anywhere, anytime we can help science learners use computing technology to extend their perceptual awareness and analysis. We start with a description of a SmartProbe and the range of educational environments in which they can be effectively used. We will address what kinds of probes can be developed, what the educational impact could be, and what kinds of standards would be helpful.

What is a SmartProbe?

A SmartProbe combines a sensor, analog-to-digital conversion, a microcontroller, memory for saving its calibration, serial communication, and power-management circuitry all into one small, convenient package. The design goal is, as far as possible within economic constraints, to increase the ease of use and reduce the opportunities for mistakes and failure. Possible features include:

Calibration. Once calibrated, a SmartProbe should remember its calibration. Using the calibration a SmartProbe could report back measured data in calibrated physical units.

Power management. SmartProbes should use as little power as possible and, whenever possible, eliminate the need for a battery by getting all necessary power from the computer's serial interface.

On/off. A SmartProbe should not have an on-off switch, thereby eliminating another source of potential confusion in the field.. Whenever an active serial interface connection is detected it should automatically turn itself on.

Standard I/O. SmartProbes should use a standard three-wire RS-232 serial communication protocol so that they can be connected to the widest range of computing hardware.

Memory. Advanced SmartProbes might include a power source and have the capability of recording data while disconnected from the computer.

Standard communications. We need to develop a communication protocol for SmartProbes to enable code, commands and data to be passed between the computer and the probe.

Educational Vision

We imagine a shoebox of sensors capable of measuring almost any physical property. With these sensors attached to an appropriate general recording device, students could begin at an early age to understand that the world is filled with interacting variables that can be measured, recorded, and understood in terms of cause and effect. Student investigations based on these data could provide the basis of lifelong learning of math, science, and technology that could be far more comprehensive, integrated, and sophisticated than current expectations. The result would be that student will understand better and sooner topics such as motion, fields, heat and temperature, water chemistry, and pollution and concepts such as variable, graphs, and slope. By making the sensors very easy to use, essentially plug-and-play, a very wide range of learners could use them regularly: kids in elementary school and home-schoolers, as well as students in a wide range of math, science, and technology courses. And finally, by realizing such widespread integration of probes into learning, we should realize volume price reductions.

This vision was first enunciated by John King at an instrumentation workshop in the summer of 1965 organized by the Commission on College Physics. At that time, the oscilloscope was the best general recording device to use with sensors to realize this dream. With the advent of microprocessors in the 1970's, it became clear to us that sensors interfaced to inexpensive microcomputers would provide a more powerful solution for education. This led us to develop in 1983 the concept of Microcomputer Based Labs, or MBL. This resulted in a spate of research on the educational implications of MBL that continues to this day.

The vast majority of the research has been around student acquisition of concepts of classical kinematics and dynamics using a motion probe and, for dynamics, a force detector. That research has shown:

The real-time nature of the display is critical in student learning. If the screen is blank during the 10-30 seconds while motion data are being collected, the learning value is negligible.

The right sequence of activities can improve student acquisition of qualitative ideas kinematics and dynamics. This sequence is more effective than any combination of lecture, traditional labs, and homework.

Another extensive strand of research has looked at the student use of a temperature probe, sometimes in conjunction with a "pulser" that can deliver a set amount of thermal energy. With a carefully designed curriculum that used probeware and focused on building and testing theories, middle school students were able to make substantial progress in understanding thermal properties of mater.

Both the temperature and motion probes have been used to introduce graphs and decimals to elementary grade students. With only a short introduction, grade four students were able to read and interpret graphs better than college freshmen in engineering. This showed that graph interpretation and production were independent skills and that graph interpretation could be taught much sooner than commonly assumed.

There are currently several major suppliers of MBL, or probeware, as well as variants such as Texas Instruments' Calculator Based Labs (CBL), Logal's Video MBL or VMBL (that shows videos of MBL synchronized with actual data), LBM (the reverse of MBL, in which a student draws a graph that results in motion), and Mouse-based Labs (where the mouse is used as an input.) Probeware hardware and student activities are available for teaching many topics in physics, parts of chemistry and biology, physiology, and ecology. Probeware systems with actuators are used in teaching technology. There are advocates for probeware use in mathematics for teaching calculus, algebra, statistics, and other concepts. Probeware has been used widely in England and has several roles in the Dutch national curriculum.

With funding from the NSF for the Science Learning in Context (SLiC) project, we have recently been studying the role of probeware in student learning in field studies, outside the lab. We have given students with Newtons and eMates equipped with probeware (eProbes), appropriate software, and activity guides. One of the unanticipated needs we identified while watching students do field work with portable computers involves the design of the probe system. In the lab, it is possible to lay out a traditional MBL system with cables, interface box, and probes, but that same system cannot just be run on batteries and expected to work well in field applications. The left-hand side of the sketch below illustrates the problem; there are simply too many wires and boxes.

<insert figure 1 here>

Not only is this unwieldy, it is error-prone, distracting, and potentially dangerous. There are too many components that can be incorrectly connected, dropped in the water, or tripped over. There are too many components to troubleshoot if something like a dead battery, bent pin, or loose connection causes one of the components to fail. We found students and teachers needed to spend too much time getting the system working and, therefore, lost opportunities to be thinking about science.

Recent advances in low-cost and low-power chips now make it possible to combine the interface, amplifier and sensor into a single SmartProbe, as illustrated on the right. Because microcontrollers are now very inexpensive, we can migrate all the intelligence from the interface into the probe package while incorporating a number of additional features that will simplify data collection and allow students to focus more on science concepts and investigations. The SmartProbe can store information about itself. Most significantly, it can store and use calibration constants and return data in calibrated physical units. This means that the SmartProbe can be used on any computer without re-calibration or copying the calibration constants.

What is the technology?

New microcontrollers and sensors are available which in the simplest case allow us to develop a smart temperature or light probe for under $10 in parts costs.

A key component is an 8-pin microcontroller from Microchip, the PIC12CE519. The PIC12CE519 costs approximately $2 a unit in 1,000 piece quantities. A key feature is the 16 bytes of EEPROM on-board. The calibration constants and other operating parameters can be stored in this non-volatile memory. At eight pins the PIC12CE519 is tiny and, if mounted in the surface mount package, it is even smaller. The controller comes with 1024 12-bit words of EPROM program memory. The program memory can be written only once because the standard packages don not have erasing windows. The controller does not have a built-in serial interface capability so we create the interface in software. Speeds up to 9600 bps are possible using this technique. A very interesting capability is that the program memory can be programmed after the chip is installed in the circuit. This, in principle, allows a completed SmartProbe to be manufactured, the sensor calibrated and a default calibration constant written out with the rest of the program memory to provide a backup default calibration. The PIC12CES19 uses approxrmately 2 mA at a supply voltage of 5 volts. You can find more information at:

http: / /www.microchip.com/ 10 /Datasheet/PlCMicros /PIC12CES19.htm

In general, for miscellaneous analog probes, we prefer a 12-bit range. This gives enough dynamic range while still keeping the individual step size small. However a reasonable 12-bit analog-to-digital converter (ADC) costs about $5 in 1000 piece quantities. Instead, for the simplest SmartProbes we use sensors which output values digitally. A more general inexpensive solution is to use an inexpensive voltage-to-frequency converter.

The TMPO3 temperature-sensor from Analog devices costs $2.50 per 1000 unit pricing. Its special feature is that it puts 6ut a pulse train whose ratio of high to low is directly proportional to temperature. Any microcontroller can measure these values without the need of an ADC. Analog Devices claim a 12-bit effect accuracy. The device uses only 1.3 mA at 5V. The sensor comes in a rugged TO-92 metal can and looks like a small transistor. For more information:

http: / /products.analog.com/products /info.asp?product=TMPO3

One last product is the Texas Instruments T5L235 Light-to-Frequency converter. This sensor costs $1.47 in a 500 unit purchase and outputs a frequency directly proportional to light intensity. It uses 2 mA of current at 5V. See:

http: / /www.ti.com/sc/docs/phs.heets/abstract/ datasht/soes0l2.htm 

The following diagram shows the main components in a temperature sensing SmartProbe.

<insert figure 2 here>

For measuring from more than one probe at a time an interface will be needed, that could also support off-computer logging from multiple inputs as illustrated below.

<insert figure 3 here>

We have wanted a motion detector to use in the SLiC research, but no field-ready version exists because of the power demands of generating an ultrasonic pulse and of the proprietary digital chip used in all designs. Thus, the motion detector was a logical first SmartProbe for us to develop. We have built several prototypes housed in flashlamp cases, using a design that kept battery consumption to a minimum. We have developed prototype software for it that runs on a Palm Pilot.

What needs to be done?

To realize widespread adoption of SmartProbes, we need parallel research, hardware development, and product development efforts.

Researchers need to explore the range of learning situations to which SmartProbes could contribute as well as the educational strategies that best exploit their capacity. Research is needed to guide probe, software, and educational design. Questions such as the following need study: What sense to very young learners make from probe data? What is the role of kinesthetic experience in learning with probes? How are data representations learned in real-time contexts? What data representations are most helpful in different contexts? Do automatic features such as calibration and graphing interfere with learning by making the connection between the real world and its representations incomprehensible? Should we explore strategies to remove the "black box" nature of this technology? What strategies are indicated: hardware, software, or instructional design?

There are so many interesting research questions, there may be a need for large-scale field implementations where collaborators could explore many of these research questions. Can CILT mount a field implementation soon? How would we recruit and support researchers and classrooms? What is a realistic timetable?

We need prototype SmartProbe hardware for research, field testing, and dissemination. Before developing too much hardware, though, we need to decide on standards for probe communication. How will a SmartProbe identify itself? In what format will data be transferred? What is the full range of potential SmartProbes and what technical problems might some create in terms of data format and control? How are calibration constants uploaded? What calibration equations will we support? Should raw data be communicated?

SmartProbes are useless without supporting software and educational materials. What software is needed? How will prototype software be produced to support research and development? What educational materials could be adapted for field research?