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

Micro-computers as laboratory instruments
Microcomputers in the laboratory
J.W. LAYMAN.
Microcomputers or personal computers are becoming so inexpensive that many parents feel that
their children wil be deprived of one of the major skills needed for the future if they do not
grow up using such devices. Parents in turn are pressuring schools to incorporate them into their
teaching, but this frequently occurs in mathematics or business areas rather than in science. These
devices have their greatest potential in science because they can allow students regularly to sample
features of the real world in time scales not amenable to the stopwatch, the mercury thermometer,
or the ticker-tape timer.
A prime example that fits in well with the theme ‘the teaching of energy,’ would be the ability
to study the properties of a solar collector using a microcomputer to obtain and display successive
temperature-time graphs as the parameters of the solar collector are changed. This is the introductory
experiment in the American Association of Physics Teachers (AAPT) one-day workshop An
Introduction to Microcomputers as Laboratory Instruments [ 1 ]. A small (1 2 cm X 12 cm X 4 cm)
chamber with a clear plastic cover illuminated by a light source contains a flat aluminium plate,
black on one side, shiny on the other, fitted with an AD590 temperature-sensing integrated
circuit that allows a current of 1pA/K to pass through it. This current is translated into a voltage
which in turn can be sensed by the laboratory interface circuitry and logged in the microcomputer
memory as a data point (a temperature). The AD590 is a transducer providing analog information
about temperature to a laboratory interface board which provides analog to digital and digital to
analog signal conversion. The digital temperature information is finally stored in the microcomputer
which also provides the program to control the collection and display of the data. An
oscilloscope, which serves as the display device, is the final part; through program control in the
microcomputer, it can display a graph of temperature versus time.
A microcomputer-based system allows students to run a succession of experiments: black
collector up, shiny collector up; using a glass cover, a plastic cover, or no cover; and with varying
intensities, distances, or angles of the light source. The microcomputer not only takes the drudgery
out of data collection, but after data collection, these successive temperature/time curves may be
displayed on the oscilloscope showing clearly the changes in the heating or cooling behaviour
associated with changing the various collector parameters. The whole experiment is designed to
aliow the graph appearing on the oscilloscope to be generated as the data are gathered, in other
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