New trends in physics teaching, v.4; The ... - unesdoc - Unesco

Microcomputers in the laboratory
analogue to the old ticker-tape timer can be used to allow simultaneous display of the position,
velocity and acceleration of a moving mass. This illustrates the ability of the microcomputer to
process data and display the results as the data are acquired.
With slightly more sophisticated electronics, one can do pulse height analysis and radioactive
half-life experiments, study rotational dynamics and study various transient phenomena by
using the system to capture a brief signal and then displaying the signal as one would with a much
more expensive storage oscilloscope.
What general mechanism might make this all feasible for the average physics teacher? A small
group of teachers within AAPT proposed that a workshop be developed. With AAPT support
and in collaboration with the Technical Education Research Center a one-day workshop was
designed to introduce physics teachers to the microcomputer as a laboratory device. The equipment
developed for the workshop included each of the elements mentioned earlier: a single board
microcomputer; a laboratory interface board containing the circuits for analog to digital and
digital to analog conversion; a set of transducers and their analog circuitry; and most important,
a read-only memory chip (ROM) resident on the laboratory interface board which contained the
program needed to carry out the experiment with the solar collector as well as all other programs
used in the workshop to introduce teachers to the microcomputer as a laboratory instrument.
Workshops or special courses are needed because most teachers received their training when
none of this technology was available, and at present the most commonly observed applications
of microcomputers do not involve interfacing with the real world in a laboratory setting. Teachers
must be given opportunities to judge for themselves whether such devices can enrich their
student’s understanding of physics.
All comments up to this point have referred to a specialized system designed to utilize a simple
single board microcomputer, a laboratory interface board, transducers and an output device.
What about the more complex microcomputers such as the Apple IT, BBC, OS1 Challenger,
Radio Shack TRS-80 or Sinclair, that offer instant and sometimes colourful graphics, that speak
a high level language such as BASIC and are purchased ready to plug in and use? What role can
these play in the laboratory? One use made of these personal computers is to play games, a
feature of which many physics teachers may be critical. It turns out, however, that the game
paddles which allow the user to control features of the game are in fact connected to built-in
analog to digital converters. In an Apple 11, a game paddle can be replaced by a thermistor whose
resistance is proportional to temperature, so that with a simple program the student can obtain a
real-time graph of temperature versus time and even superimpose this on a graph background.
The cost of the thermistor, its connecting wire, and connecting pins is really quite low, allowing
a teacher to convert a machine that might have been used simply to solve equations and plot
standard functions in the maths or science class, into an active laboratory device; one with a
large memory and built in programs for producing real-time graphs of physical phenomenon. The
thermistor is an example of a device whose resistance is not linearly related to its temperature.
Thus, to plot the actual temperature, the computer must first solve the nonlinear relationship
between resistance and temperature, a task which it does easily.
Many of these microcomputers are also designed to produce musical tones as one output
function. The device which produces the tone is actually a digital to analog converter, which was
again provided on the laboratory interface board. So one can see that the more costly microcomputers
may be used as laboratory devices with input and output interfacing capabilities if
the teacher gains enough experience through the mechanism of a workshop or a course to use it.
I must apologize to the teachers who read this discussion and find the vocabulary quite new
and the devices not available in their own countries, and who have had no opportunity to gain
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