An inexpensive Digital Data Acquisition System tor the Teaching Laboratory A major impediment to the use of digital data acquisition in the teaching laboratory is cost. During the past two years a variety of devices known as UARTs (Universal Asynchronous Receiver Transmitters) have become available. General descriptions of these devices and their potential uses have been presented by Larsen, Rony, and Titus in a series of recent papers.' The purpose of this note is to make accessiblea detailed circuit diagram for a practical system which will convert analog data to digital data in printed and more importantly, for subsequent data reduction, punched-paper tape form. The system is applicable to slaw-scan spectrometry, automatic titrations, or any other techniques in which a sampling rate of 1sec-' or slower is acceptable. The system uses a 3% digit panel meter, an Analog Devices' SerdexTumodule with clock, and a Teletype' model ASR teletypewritter (see figure).
Voltage Input
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SERDEX@ MODULE
M
OOOC
ASR TELETYPE0
Parallel Data Transmission
me block dlagram of me digital data acqulsltian system.
Tape
Excluding the m t of the teletypewritter, which need not be dedicated to the UART, the entire system, including chassis, panel meter, power supplies and hardware, can he assembled by a novice for about $650 in a total of about 50 hours using wire-wrap connections. The circuitry employed in this system will: 1) sample a 3KBCD digit panel meter with polarity a t a r a t e of 1see-' or less. The upper limit is set by the BAUD rate of the teletvoewritter , 2) prowde n mrrlage return to the teletypewr~tcr.and 31 provide a lme teed to the teletypewrrtter
.
Although the appropriate circuitry ean be deduced fmm Analog Devicea' literature, considerably more time was expended in designing the correct circuitry than in actually building the system. A detailed circuit diagram and description can he obtained by writing the authors. Larsen, D. G., Rony, P. R., and Titus, J. A,, ArnericanLoboratory, 7(2), 113 (1975); 7(4), 93 (1975); 7(5), 116 (1975); and 71fi). . ,.,,78 . .11975). ,- .. .,.
Current address: Department of Clinical Pathology, University of Oregon Medical School, Portland, Oregon.
'To whom correspondence should be sent. University of Georgia Athens, 30602
786 / Journal of ChemicalEducation
Larry F. Whiting L a r r y D. BowersZ P e t e r W. C a r 9
