Birlasekaran, S.

Chandrasekaran, R.

Kalidoss, R.

Thirumalai, P.

IR@CECRI

lMTWRVaION & u p p k t i ~ ~  f ~ q m  test sys(pll bas bcq increaripg rapidly blws,  which ore time consuming and @y to wlve. In this laboratory, Tin FMf YW4 15-81 . MVRRF~S in cslpputing tccbology have spawn- a preliminary attempt hao beep mode to @terface a 8-bit '&-@I qicroe4m- #I {M pp~v p~alrUm sf 1 1 ~ ? p ~ t @  a.q&jcal ipstNlqcntation. Transfer putcr system (Data Wealth. In*) with two ~ u t p u t  prto and 8 data ac- sf h~ fi~p -M fa tpimwmp~fm WRiGR we capable of graphic quiriw IutJ$a85 microproccswr jrit. Very cn~umd!qt regulu have been ~ f l  m p @ # j o ~  k ym q p ~ h  m w  fm arllJysis and prcdic- obtaim.  In this communicatiau, the salient points are V@ighted. den, nus miqwwq?yky pecoslca ag integral part of eitber control, data  miti ti on or data M # l p n .  F'UNCW#AL !?-ON The aplqption qt wb # FYrtcrq can present serious interfacing pro- The general layout of the measuring system is shown in Q.1. b INTEL < 3 A/D CONVERTQR (up KIT I VOLTAGE I I CONVERTER I Birlasekaran eta1 - Microcomputer based measurement , r- 4' qTy.. v * .--- " . *. -- * -  . The ,w side Of FQ.1 forms & q-ring end of the system. IMP@DANCE/CYCLIC V Q L T W 0 G R A . W  [t consists of Intel 8685 kit to m u i r e  and tramfa data tdperipheral devices, CHRONOPOTEPJTIOM&laY D/A converter to translate digital inputs to  analog wntrol output, VCO to generate ac s w  of frequency controllad by the input voltage, A.C. Im- I I K . W ~ ~ ~  sm@m rystem, a current-to-voltage converter to read the response from the system Fig.1 brief5 @P measurement system. InitiaJ parqekm on range of fre- and A/D converter to  convert analog output to  digital input. Intel 8085 quency bit s d d o n  e&. arc kycd in micr0compWg. Micrc)comA3lt4 works micrcoprocessor kit collects the current response for vario"s programmed out the dc voltage required for gcqqation of such frequencies from VCQ Frequencies and stores them in its ram locations. The left hand side of F i .1  characteris& &@ which had bcq keyed in earlier. The computed data Forms the analysing and displaying part of the system. viz. microcomputer and machine language programme to  do ac impedance measurement are rvstem. transferred from computa to the microprocessor kit. Microprocessor col- The sequence of measurement is listed below: leas the data on iq~pedance aql phase fo; eaph Jelected fmue&y and stores it in its RAM. At the end of it. hand shaking between comnuta and -I) Initialization and initiation sequences for the selected mode of measure- icroprocessar js ioitiated to trppk on impedance and p b  frpm ment. This is mainly wjtten iq high level language in /be m i ~ o c o m a y t g  w ~ ~ p r - w r  114\M to  i c r w p p y t e r  plemory. In an interactive mode for more flexibility, yiz (a) furjng up the range qf frequencies, (b) accuracy limit etc. ii) Transfer the appropriate measuring softwqe in machine language from microcomputer file to  the ram locations of the microprocessor kit. iii) Data acquisition by the microprocessor kit as per the loaded program [Step-2) iv) Transfer of the acquired data from microproceswr to microcomputer. v) Analysis and proper display of output from microcomputer. The complete series of programming has to  be done in both machine and high level languages and they are executed sequentially using CP/M com- mands in an automatic way. Programmes for data acquisition and analysis in t k q  electrochpical measuring systems have been written and the results are presented in figures 1 to 3. Fig 2: Graphical plot of imped4np diagram I Pig.3: Graphical plot of c,~cIic vot'tammogmm Bulletin of Electrochemistry Vo1.2(4) July-August 1986 Birlasekaran eta1 - Microcomputer based measurement 1 Microcomputer high-level bas~c programme fits a semicircle to the ~ m -  CONCLUSION pedance results after evaluating the real and imaginary parts. It gives out 1, this paper, the preliminary results obtained in an automated microcom- the radius and centre of the fitted circle. Corrosion rate in terms of polarisa- puter based measuring system is on three typical ~h~ main tion resistance or any other evaluation of kinetic parameters using the above advantage viz the production of completely analysed e~ectrochemical results results could be done by adding software. Graphical plot of the result ob- is described. ~ ~ ~ t h ~ ~  details on hardware and software will be published tained for a simple passive RC network is shown in Fig. 2. shortly. Cyclic Voltammogram-set up Acknowledgement: The authors thank Sri Y Mahadeva Iyer, Head of Elec- initial conditions on sweep rate, peak magnitude of the traingular wave trochemical Instrumentation Division for his interest in this work. and dc bias could be programmed in a digital function generator [4,5]. otherwise a conventional analog function generator could be preset and REFERENCES actuation signal may be issued from microprocessor kit. In the latter case, 1. T G M van den Bett and H Krketens, Computers and Chemistry, 8-3 computer acts as a transient recorder. Using two A/D converters, the analog (1984) 169 signals on voltage and current from potentiostat are digitized and stored in RAM of microprocessor. At the end, microprocessor and computer hand- 2. M L Salit and M L Parsons, Anal Chem, 57-6 (1985)715 A shake and transfer the data to a file memory in computer. Any processing of the waveform like programmable integration could be done more precise- 3. Stuart A Barman* Chem 57-8 (l985) 983A ly now i6J .  The acquired data is plotted using MAKEGRAPH utility pro- gramme as shown iil Fig. 3. 4. V Ananth, S Birlasekaran, and H N Venkoba Rao, A Microprocessor based function generator for electrochemical study, 3rd Interna Symp Chronopotentiometric stripping analysis on Adv in Electrochem Sci & Tech, Madras, India, Dec. 10-14, 1984 The data C7lis loaded into the microprocessor. Transferring the data mto the microcomputer, differentiation in high level language has been done 5, Narayanan, Raghunathan and Sundararajan, A to evaluate trace concentrations of cobalt and nickel in the water sample. . Sweep Generator for cyclic voltammetry, Symp on Anal IILFtr and Tech The pcaks could be seen clearly ir! Fig. 4. in Electrochem, Karaikudi, India, Dec.5-7, 1985 b,g4(a) Experimental resul.3 6. S Birlasekaran, K R Ramakrishnan, and H N Venkoba Rao, Chem, Biomed and Environ Instru, 11-3 (1981) 1 7. H Eskilsson, C Horaldsson and D Jagner, Anal Chim Acta, 175 (1985) 79 Bulletin of Electrochemiistry Vo1.2(4) July-August 1986 439 

Microcomputer based computer system

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