Chemical Instrumentation for the Visually Handicapped James L. Anderson University of Georgia, Athens. GA 30602 Much effort has been focused recently on increasing educational opportunities for the handicapped' (1-11). Relatively little appears to have been published on chemistry (1-9) or physics ( 1 0 , l l ) for the visually handicapped. The inherently experimental approach of chemistry demands maximum exposure of all students to laboratory experience. Chemical instrumentation represents an important part of the chemistry curriculum, which seems ideally suited to enable fuller participation of the handicapped-especially the visually handicapped-in the chemical laboratory. Just as chemical instrumentation serves as an additional sense a b w r and heyund the conventional f k e senses to the nm-handicapped, prowding inikmation in dim~nsiooswhich - we cannot perceive or quantitate, it provides one of the most direct links to the chemical world for the handicapped. Chemical instrumentation typically transforms quantitative chemical information into electrical outputs transformable into a number of formats which can be sensed and interpreted by the observer. Descrihed here is a very simple, relatively inexpensive, and easily implemented approach developed a t North Dakota State University2 for introducing visually handicapped students to chemical instrumentation, via experiments on operational amplifiers as examples of some of the electronic building blocks of chemical instrumentation. However, the approach is generally applicable to a wide variety of chemical instruments having electrical outputs of experimental variables. A similar approach to the teaching of physics has been described (10).
Figure 1. Experiments1schematic iiiushation. A, Input signal sowce; 8, DVM input: C, sliding template; D. Optacon readout head; E, Optacon vibrating rods.
The Apparatus
The key transducers needed to transform the electrical data into a format verceotible hv the blind student are a diaital multimeter eq;ipped with light-emitting diode (LED) digital output, and an Optncon,'equipped with a photosensitive hwd capahle of perceiving thr LED digital display. 'l'he Op~aron transduces images (letters, numbers, etc.) into rapid motion of a set of vibrating rods on which the user places a finger. The pattern of vihratingrods mimics the image so that the user can interpret it. With relatively little practice, it is possible to determine the output of the multimeter digital display from the tactile sensations of the vihrating rods on the finger. Weems has described use of a similar combination of digital multimeter and Optacon in physics laboratory experiments
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A very simple cardboard template and guide was fashioned to position the readout head of the Optacon for proper alienment with the LED o u t ~ u tof the voltmeter. The ~ e y t h l e yModel 178,4112digit mLltimeter used here was convenient due to the linear alienment of the edee of the case with the digital display. The cardboard guide was constructed to
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Section 504 of the Rehabilitation Act of 1973, P.L. 93-1 12, passed by the US. Congress, requires equal access and opportunity for the handicapped. Numerous local efforts have been stimulated by this legislation to improve access to facilities previously inaccessible to the physically handicapped. This work was carried out in the Department of Chemistry at North Dakota State Universitv. . Faroo. ND 58105. Tne Optacon is made by Telesensory Systems,inc .3408 H~llv~ew, Box 10099. Paio Alto. CA 94304 Although conslderaole practce is needed to read conventional pr nted text with the dev~ce.the large sue of the LED display makes readout less difficult.
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Figure 2. Operational amplifier menifold with a layout partially illustrated which Contains six built-in operational amplitiers. slide along the top edge of the multimeter case. The guide edges were sized to restrain the guide from moving too far to either side of the digitsshown in the display. The experimental setup is illustrated schematically in Figure 1. The digital multimeter-Optacon readout approach has several maior advantaees. Inex~ensivedieital multimeters. commonly~vailableinihe laboratory, canreadily measure wide varietv of instrumental outwts. . . with much hieher accuracy and precision than attainable with analog hridye-type meters tfcaturine audihlc o u t ~ ~ to u tenable detection uf t~alance conditions) such as descrLbed previously (2). In addition, the increasing use of Ootacons as an alternative to Braille for direct reading of conventional text mat~rialprovidw a tool serving double duty to the blind studrnt hoth as a study aid and as: a laboratory transducer. (Reading nf text requires a different readout head frrm those u a d with the muliimeter.) The digital multimeter-Optacon readout approach is applicable to any situation where a sighted person would use a meter or readout to extract the analytical information, i.e., for any experiment whose output does not change too rapidly (no more than several sequential outputs per minute). For experiments with rapidly changing output, or scanning experi-
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Volume 59 Number 10 October 1982
871
ments (e.g., scanning spectrophotometry), an intermediate storage device.. e.e.. ...a microcornouter, would be desirable to hold ;he output to make it availa.hle a;il rate amenable to the multimeter-Optacon readout. More sophisticilted readout dr\.ir.ts now becoming available utilize talking digital multimeters and talking instruments (5.91,including the use of n~icrocomputer(91.The chief advantages of the present ap. proach are its favorable economics and the possibility of utiiizing equipment which is also useful to the studentoutside the laboratory. operationil amplifier experiments were devised witha locally constructed operational amplifier manifold with a layout ~ a r t i a l l villustrated in Fieure 2. containine six built-in overkiooal"amp1ifiers. The rayout is simi1a;to those of units nreviouslv available from ooerational amolifier manufacturen such as Analog Oevices orwo wood. or and Telrhyne Philbrick tnedham.. MA). . Pin iacks were arraved hexaronallv on 314-in. centers to accommodate double pin plugs. (~&anaj&ks and vluas. or anv other standardized olue-in arrangement wvuid aiso he sukablc.) The houndarirs o; key regions and functions on the manifold were delineatrd bv the use of r a i d tape. Thus, six zones, one associated with-each operational amplifier and associated jacks, could be delineated by vertical tape strips. Braille embossed tape could also he used to label each zone. The trianeular outline re~resentinaeach operational amplifier was delineated withtape. w he student was informed of the usual conventions that the inverting and nun-mverting input jacks were found at top and h&m on the left, and the outout lack was found on the riaht ins~dethe outline in raised tape of the operational amplifier. Raised tape lines connected jacks that were internally connected together. Ground jacks were delineqted by a surrounding tape triangle near the hottom of each operational amplifier jacks array. Lateral tape strips helped to differentiate clusters of jack with different functions. Tape strips used to differentiate zones and clusters are shown as doublelines, while internal connections between jacks (also dplineated by~. tape strips) are S ~ O W I Ias single lines in Figure 2. In this way, the blind student could readily identify the input, output, and auxiliary jocks associated witheach ;periltional amplifier. Voltage off3et trimming was periormed for the student, since the trimpots were not readily accessible from the front panel. Remounting of the trimpots in a more accessible position would facilitate student adjustment of offset. As a typical illustration of a possible evaluation circuit, dotted lines and resistors R1 and R2 represent shorting straps and nassive circuit comoonents needed to transfer an invut to oierational amplifie;~, configured as a voltage follower, and amplify the output of operational amplifier A by a factor of -(RZ/Rl) to obtain a voltage measurable by the student a t the o u t ~ uof t ooerational amplifier B, confiaured as an inverter with gain.'~umbered jacks indicate where external
components are connected. A collection of circuit components (primarily resistors and shorting wires) was pre-soldered to double pin jacks. Screw-type double hanana plugs and jacks would have enabled the student to select resistors and assemble plugs as needed. Discussion The student used the multimeter-Optacon system to determine the precise resistance of each resistor and marked them with Braille-embossed olastic tape4 for easv future identiticarion. This approach irovided structured format tosimpliiv workma with the apparatus, but enabled thestudent to work with it in a largeiiindependent fashion. The student successfully performed a number of experiments evaluating the properties and performance of numerous operational amplifier configurations a t low frequency, including voltage followers, current amplifiers, summing amplifiers, and even an integrator with a long time constant. Coupling of the 4% digit multimeter with the Optacon enabled measurements with precision and accuracy better than 0.1%. Data were recorded by the student by means of a Perkins B r a i l l e ~Extension .~ of this approach to a wide range of experiments in chemical instru&ntiltion is straightf;rward. It should he noted that handlinz of chemicals and Drocesses i n t h e laboratory (especially use of hazardous chemicals o r open flames o r burners) is potentially hazardous even to a sighted person. Thus, a l l laboratory procedures should be carefully chosen, a n d careful supervision should be offered t o minimize hazards f o r a blind student i n t h e laboratory. On the other hand, many of the ooerations ussociated with use of chemical instrunrvnrotron ore rvlorir~pl)nonhoznrdous und should pow no ~ n s u r m ~ ~ u n t aborrivrs ble to rho blind student. as illustrated by an earlier report on the potentiometric titration of acids and bases (2). There would appear to be numerous opportunities for blind students to gain first-hand experience in chemical instrumentation and instrumental analvsis. T h e simple approach described here provides a straightforward vehicle to helu I~reakdown the barriers which have orevented the blind from participating in the chemical instrumentation laboratow. I t is a pleasure to report that the student involved in this exoeriment comoleted a B.S. degree in chemistrv and is currently in graduate school succe~sfullypursuing a Ph.D. in chemistry.
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Literature Cited (1) Hiemanr, P. C., and Pfeiffer, E., J. CHEM. EDUC., 49,263 (1972). (2) Tallman. D. E.. J. CHEM. EDUC.. 55.605 (1978).
(3) 6th Biennial Conferenceon ChemicalEduestion, Raeheste.. N.Y., Juoe2226.1980. " N o h 6th.'' Papers 21-24 summarize approaches fo educating the handicapped io science:see conference summarv inJ. CmM. Eouc.. 58.8 119811.
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Braille tape embossers are available from Appliance Division, American Foundation for me Blind. 15 West 16th Street, New York, NY 10011.
5Braillers are available from Howe Press, Perkins School for the Blind, 172 N. Beacon Street. Watertown, MA 02172.
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Journal of Chemical Education
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Tombaugh,D.,J.CHEM.EouC.,58.222 (1981).
D., J. CHBM. EoUC.,58.228 (1981). (9) Lunney, D., and Marriaon. R. C.,J. CHEM.EDUC..58.228 (19811. IlO) Weem%B.,Phys. Teoch., 15,333 (1977). (11) Baughman, J.,andZallman,D.,Phys.Teach., 16,339(1977). (8) Smith.
