Interfacing in the Biology Laboratory: State of the Art

Abstract

It is commonplace now to see microcomputers used in the science classroom, especially for drill and practice, review, testing and other tutorial functions. For several years microcomputers have been used for data analysis and computations such as statistical analysis. Just a few years ago, a new dimension was added by interfacing the microcomputer to the videodisc player. Several applications and programs using the interactive videodisc have been described in this column and elsewhere (Leonard 1983, 1985). The main advantages of this new videodisc technology are broadcast-quality video images, greater speed in assessing video materials and more extensive interactivity for the user. The interfacing of laboratory instruments to the computer has been done in industry and scientific research almost as long as the computer has existed. This application has been the source of many ideas for current classroom use of interfacing. Only in the past two or three years has interfacing been used with success in the science classroom, primarily because of increased activity in classroom use of the microcomputer. This article will focus on some of the very basics of interfacing, what is now state of the art and the educational benefits of computers interfaced to laboratory instruments for use in biology classrooms. The simplest possible interface consists of a switch connected by two wires to a port in the microcomputer. The computer can detect if the switch is on or off approximately 80,000 times a second. The switch can be replaced by a photodetector and interruptions in the beam can be timed over very short or long periods of time. Instruments that have a signal output, such as pH meters, spectrophotometers and chromatographs, can be connected directly to the computer. If measurement of continuous variables such as temperature or light intensity is desired, an analog to digital converter (ADC) is added. ADCs are basically transducers which convert the input variable into a voltage or resistance. A thermister can measure temperature and a phototransistor can measure light intensity. Transducers can also be used to measure humidity, radioactivity, pressure and the presence of various gases (Nicklin 1985). Most of these take advantage of the built-in game controller or paddle port found in most microcomputers. Typical paddle ports can read a variable resistance in the range of 0-500 kiloohms. There are many other possibilities.