A versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat uses readily available electronic components and an interface is detailed which allows the potentiostat optional computer control

Bratton, P. D.

Fuller, Gary L.

Hawk, Roger M.

Russell, William A., Jr.

Wilson, James D.

English

ScholarWorks@UARK

Journal of the Arkansas Academy of ScienceVolume 43 Article 101989Versatile Potentiostat with Optional ComputerControlGary L. FullerUniversity of Arkansas at Little RockWilliam A. Russell Jr.University of Arkansas at Little RockRoger M. HawkUniversity of Arkansas at Little RockJames D. WilsonUniversity of Arkansas at Little RockP. D. BrattonUniversity of Arkansas at Little RockFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the VLSI and Circuits, Embedded and Hardware Systems CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationFuller, Gary L.; Russell, William A. Jr.; Hawk, Roger M.; Wilson, James D.; and Bratton, P. D. (1989) "Versatile Potentiostat withOptional Computer Control," Journal of the Arkansas Academy of Science: Vol. 43 , Article 10.Available at: http://scholarworks.uark.edu/jaas/vol43/iss1/1032Proceedings Arkansas Academy of Science, Vol. 43, 1989A VERSATILE POTENTIOSTAT WITHOPTIONAL COMPUTER CONTROLGARY L. FULLER, WILLIAMA. RUSSELL, ROGER M. HAWK,JAMES D. WILSON, and P.D. BRATTONUniversity of Arkansas at Little RockDepartment of Electronics and Instrumentation2801 S. UniversityLittleRock, AR 72204ABSTRACTA versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat usesreadily available electronic components and an interface is detailed which allows the potentiostat optionalcomputer control.INTRODUCTION balanced against this preset potential. The difference or error signalis fed back into a control amplifier which varies the output of thecontrol amplifier as necessary to maintain the preset potential. Theapparatus thus willreduce or increase the cell current and also willfollowpossible changes of the cell resistance as the electroactive species areconsumed. Essentially no current flows through the RE circuit, and itspotential, therefore, remains stable because of the extremely highinput impedence ( > 10" ohms) of the electrometer operational amplifierused to sense the potential of the reference electrode.Countless articles describing applications and circuit designs for threeelectrode potentiostats have appeared since introduction of this poten-tial control technique in the late fifties.The basic function of a potentiostat is to maintain the potential ofa working electrode (WE) at a desired fixed value, or to control thatpotential under a defined functional variation withrespect toa referenceelectrode (RE). Toperform a simple electrolysis under constant poten-tial conditions, the working electrode voltage must be maintained ata fixed value. This constant potential should be maintained regardlessof any fluctuations of electrolytes, current, solution resistance,temperature, or other factors. The potential of the WE is measuredagainst a RE when the RE is placed very near to the WE via an ap-paratus such as a luggin capillary (Skoog, 1985). The desired potentialis preset into the potential control circuit either manually or by com-puter control. The voltage difference, E (WE-RE), is sensed andCIRCUIT DESCRIPTIONThe described potentiostat is a versatile high precision instrumentcapable ofcontrolling a range ofpotentials (± 5 volts at the referenceelectrode) at a maximum current of 12S ma for application to a widevariety of electrochemical experiments.Figure 1rowrn surnv section OUTPUT STAG*32Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10Published by Arkansas Academy of Science, 1989Proceedings Arkansas Academy of Science, Vol. 43, 198933Gary L.Fuller, William A.Russell, Roger M. Hawk, James D. Wilson and P.P. BrattonThe heart of the potentiostat is the two operational amplifiers andtransistor network as shown in the output stage of Fig. 1. Amplifier1 is a FET input amplifier which buffers the reference electrode voltageby minimizing any reference electrode current. Amplifier 2 is used tosum the constant voltage set by the programming voltage section andthe voltage sensed by the reference electrode. As shown, the electro-chemical cell completes the feedback path and any voltage changes atthe reference electrode are coupled to the inverting input of amplifier2 such that its output varies the electrochemical cell current via the twotransistor (Aand B) push-pull current booster. Thus, the controlledcurrent output maintains a constant potential between the workingelectrode and the reference electrode. Transistors Cand D were addedto limit the cell current. Ifthe user needs more current, a Darlingtonarrangement could be incorporated. A high voltage amplifier (amplifier2) was used to increase the cell potential range.In order to select a reference voltage, a stable source is required.Amplifiers 5 and 6 in the programming voltage section use a constantcurrent configuration and a Zener diode's voltage stability to providea stable input voltage foramplifier 5 and subsequently amplifier 2. A10 turn potentiometer is used to vary the programming voltage. ResistersRl and R2 can be adjusted to change the reference voltage range.The second part of the circuit is the current monitor. Operationalamplifier 3 and the two transistors attached to the output (pin 6), andRL (10 fl, 1 watt) form a transresistance amplifier, better known asa current-to-voltage converter. The two transistors provide extraoutput current for the operational amplifier which is limited to amaximum of12 ma. The input (pin2) ofoperational amplifier 3 is forcedto remain at ground potential by virtue of negative feedback. Anycurrent flowinginto the circuit is balanced by current leaving the inputthrough RL; therefore, the voltage of the output ofthe transresistanceamplifier is proportional to the input current which is the total currentthrough the electrochemical cell. The resultant output voltage foramplifier 3 follows the relationship: Vout = (Icdl)•RL. The output ofthe transresistance amplifier is inverted and scaled by the invertingamplifier 4.A double pole-double throw switch was added in the current monitorsection. The double pole-double throw switch selects one of twocircuit modes; current calibration or potentiostat operation. In thecurrent calibration mode, a known current passes through the 300 ohmprecision resistor to the current monitor circuit. A 5 kiloohm 10 turnpotentiometer is adjusted to give the correct voltage output to thecurrent display.Two digital panel meters are required tomonitor the reference voltageand the electrochemical cell current. The reference voltage was monitoredat the output of the buffer amplifier 1 and the total cell current wasmonitored at the output of amplifier 4.COMPUTER CONTROL FOR THE POTENTIOSTATA computer controlled digital-to-analog converter was added to thepotentiostat to provide greater flexibility. A 12-bit National Semi-conductor binary multiplying digital to analog converter DAC1222(DAC) was chosen to provide the conversions. The 12-bit DAC alloweda resolution of0.00244 volts per step over the chosen +5 to -5 voltagerange. Aninterface was constructed between the computer and the DAC,as shown in Fig. 2, which consisted of an address decode and variousdata latches to support the DAC.The interface between the computer and the DAC was designed sothat it could be used withother IBMcompatible computers. AnIBMXT-compatible was used in this laboratory. The DACinterface required±15 volts at approximately 20 ma and +5 volts at approximately 130ma. The ±15 volts were provided by the potentiostat power supplysection and the +5 volts were provided by the computer.Output voltage data were taken directly off the data bus and loadedinto two octal data latches (74LS373), one at a time. After bothlatches are loaded, a second pair of latches are pulsed and the voltagedata are transferred to the DAC for conversion. Care was taken toensure that the latches were in close proximity to the data bus. Smalldistances (less than one foot) will ensure clean, valid output voltagedata to the latches. The first pair of latches was used to change the8-bit data bus of the computer to 12-bits required by the DAC. Asecond set of latches was used in this design since the DAC did nothave an enable line for conversion initiation. Thus, the voltage data(all 12-bits) could be transferred to the DAC simultaneously permit-ting the DAC to convert the correct voltage data instead of two piecesof data. Two allow the 12-bit DAC bipolar voltage swings, a LF356JFET input OP-AMP was used (Fig. 2). Equations for the resistors are(National Semiconductor Corp., 1982):AV = Peak Voltage out / Voltage referenceR4 = (2 Av- 1) RRl = R2 (Av- 1) / AvR3 = Rl :: R2,where R ¦ 10,000 ohms, R2 = 2500 ohms, and the voltage reference= 2 volts.Potentiometers were used for the resistance values to allow finaladjustment of the DAC to eliminate any offsets caused by varyingcomponent tolerances. Resistor R2 was used to zero tolerance differencesfound in the linear op-amp while resistor R4 was used to adjust the± peak voltages in the design. Resistor R3 was found to be the mostcritical in allowed tolerances.Abasic program to control the potentiostat is included in Appendix 1.33Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10http://scholarworks.uark.edu/jaas/vol43/iss1/1034Proceedings Arkansas Academy of Science, Vol. 43, 1989A Versatile Potentiostat With Optional Computer ControlAPPLICATIONSThis design provides a versatile instrument which may be used fora wide range of electrochemical applications. It is the intent of theauthors to use the potentiostat as a teaching tool in a graduate levelcourse in electrochemistry. Inthis role the instrument willbe used toplate copper from solution, demonstrate electrolysis of solvents andionmigration, and generally familiarize students with the various aspectsof electrochemical systems.The current application of concern to the authors is the anodicoxidation of PCB's. Ithas been shown that PCB's may be oxidizedat a ruthenium dioxide anode (Laule et al., 1986). This initial successwith4.4'PCB has prompted work to optimize the reaction conditions.The reaction is carried out on a 5ppm solution of PCB in a 50/50 aceticacid/water solution. An oxidizing agent such as potassium persulfateis added and the solution subjected to a potential of 2.00 volts versusa silver/silver chloride reference electrode for 48 hours.The present work is an attempt to optimzie the yield ofthe reactionat room temperature. The variables of concern are: time of reaction,applied potential, oxidant used, and exposure to UVradiation. Initialresults indicate that the exposure of the reaction cell to UV light great-lyenhances the yieldof the reaction. Notenough data have been receivedto make any predictions as to the effect of other conditions on thereaction.APPENDIX 1after conversion voltage is in form"111111111111"low$ will take the right 8 bits for loading into latcheshighS will take the left four for loading into latcheslow$ = right$(bin$,8)high$-left$(bin$,4)convert low binary to decimal.conversion fo the lower 8 bits back to decimal for output tothe latches11 = 0 :bits = 1for x = 1 to 8shifts = right$(low$,x): shiftS = left$(shift$,l)ifshifts = "1" then 11 = 11 + bitsbits =bits*2next xprint "lowload ";11;convert high binary to decimalconversion of the high 4 bits into decimal for loading into thelatchesComputer Control for the Potentiostat 10-29-88'THIS PROGRAM WRITTEN FOR THE QUICKBASIC COM-'PILER. IT CAN BE MODIFIED TO FIT YOUR NEEDS.1) Voltage entered (+5 to -5 volts) and converted to positivevoltages only.2) Voltage is converted to its decimal equivalent voltage 0.0024414volts per step3) Voltage is converted to binary form"111111111111"4) The high four and low eight are converted back to decimal5) Voltage data loaded into the latches and transferred to DACstart:input"enter voltage ",voltvolt = volt + 5.00 :'changes the voltage to positive onlyvolt = cint (volt/.0024414)print "decimal convert volt ",voltconverts voltage to binaryx = 2048:bin$convert:voltl = (volt- x)if voltl >= 0 then bin $ = bin$ + "Vifvoltl < 0 then bin $ = bin$ + "0"if voltl >= 0 then volt = voltlx = x / 2ifx < 1 goto continuegoto convertcontinue:12 = 0 :bits = 1for x = 1 to 4shifts = right$(high$,x)shifts = left$(shift$,l)if shiftS = "1" then 12 = 12 + bitsbits = bits * 2next xprint "high load ";12the loading of the latches654 dec = 28E hex load latch one653 dec = 28D hex load latch two651 dec = 28B hex strobe data to datprint "loading the d / a ",qout 654.11out 653,12;'load one (1 );'load two ( 2 )print "output enabled",qout 651,0 ;'output enablegoto startendLITERATURE CITEDLAULE,G., R.M. HAWK, D. MILLER.1986. Oxidation of 4,4'-dicholorobiphenyl at a ruthenium dioxide anode. J. Electroanal.Chem., (213).NATIONALSEMICONDUCTOR CORP. 1982. Linear Databook.Santa Clara, CA.SKOOG, D.A. 1985. Principles of Instrumentation Analysis. ThirdEdition. Saunders College Publishing, New York, NY.34Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10Published by Arkansas Academy of Science, 1989

Versatile Potentiostat with Optional Computer Control

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 43 Article 10 1989 Versatile Potentiostat with Optional Computer Control Gary L. Fuller University of Arkansas at Little Rock William A. Russell Jr. University of Arkansas at Little Rock Roger M. Hawk University of Arkansas at Little Rock James D. Wilson University of Arkansas at Little Rock P. D. Bratton University of Arkansas at Little Rock Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the VLSI and Circuits, Embedded and Hardware Systems Commons Recommended Citation Fuller, Gary L.; Russell, William A. Jr.; Hawk, Roger M.; Wilson, James D.; and Bratton, P. D. (1989) "Versatile Potentiostat with Optional Computer Control," Journal of the Arkansas Academy of Science: Vol. 43 , Article 10. Available at: https://scholarworks.uark.edu/jaas/vol43/iss1/10 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. 32Proceedings Arkansas Academy of Science, Vol. 43, 1989A VERSATILE POTENTIOSTAT WITHOPTIONAL COMPUTER CONTROLGARY L. FULLER, WILLIAMA. RUSSELL, ROGER M. HAWK,JAMES D. WILSON, and P.D. BRATTONUniversity of Arkansas at Little RockDepartment of Electronics and Instrumentation2801 S. UniversityLittleRock, AR 72204ABSTRACTA versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat usesreadily available electronic components and an interface is detailed which allows the potentiostat optionalcomputer control.INTRODUCTION balanced against this preset potential. The difference or error signalis fed back into a control amplifier which varies the output of thecontrol amplifier as necessary to maintain the preset potential. Theapparatus thus willreduce or increase the cell current and also willfollowpossible changes of the cell resistance as the electroactive species areconsumed. Essentially no current flows through the RE circuit, and itspotential, therefore, remains stable because of the extremely highinput impedence ( > 10" ohms) of the electrometer operational amplifierused to sense the potential of the reference electrode.Countless articles describing applications and circuit designs for threeelectrode potentiostats have appeared since introduction of this poten-tial control technique in the late fifties.The basic function of a potentiostat is to maintain the potential ofa working electrode (WE) at a desired fixed value, or to control thatpotential under a defined functional variation withrespect toa referenceelectrode (RE). Toperform a simple electrolysis under constant poten-tial conditions, the working electrode voltage must be maintained ata fixed value. This constant potential should be maintained regardlessof any fluctuations of electrolytes, current, solution resistance,temperature, or other factors. The potential of the WE is measuredagainst a RE when the RE is placed very near to the WE via an ap-paratus such as a luggin capillary (Skoog, 1985). The desired potentialis preset into the potential control circuit either manually or by com-puter control. The voltage difference, E (WE-RE), is sensed andCIRCUIT DESCRIPTIONThe described potentiostat is a versatile high precision instrumentcapable ofcontrolling a range ofpotentials (± 5 volts at the referenceelectrode) at a maximum current of 12S ma for application to a widevariety of electrochemical experiments.Figure 1rowrn surnv section OUTPUT STAG*32Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10Published by Arkansas Academy of Science, 1989Proceedings Arkansas Academy of Science, Vol. 43, 198933Gary L.Fuller, William A.Russell, Roger M. Hawk, James D. Wilson and P.P. BrattonThe heart of the potentiostat is the two operational amplifiers andtransistor network as shown in the output stage of Fig. 1. Amplifier1 is a FET input amplifier which buffers the reference electrode voltageby minimizing any reference electrode current. Amplifier 2 is used tosum the constant voltage set by the programming voltage section andthe voltage sensed by the reference electrode. As shown, the electro-chemical cell completes the feedback path and any voltage changes atthe reference electrode are coupled to the inverting input of amplifier2 such that its output varies the electrochemical cell current via the twotransistor (Aand B) push-pull current booster. Thus, the controlledcurrent output maintains a constant potential between the workingelectrode and the reference electrode. Transistors Cand D were addedto limit the cell current. Ifthe user needs more current, a Darlingtonarrangement could be incorporated. A high voltage amplifier (amplifier2) was used to increase the cell potential range.In order to select a reference voltage, a stable source is required.Amplifiers 5 and 6 in the programming voltage section use a constantcurrent configuration and a Zener diode's voltage stability to providea stable input voltage foramplifier 5 and subsequently amplifier 2. A10 turn potentiometer is used to vary the programming voltage. ResistersRl and R2 can be adjusted to change the reference voltage range.The second part of the circuit is the current monitor. Operationalamplifier 3 and the two transistors attached to the output (pin 6), andRL (10 fl, 1 watt) form a transresistance amplifier, better known asa current-to-voltage converter. The two transistors provide extraoutput current for the operational amplifier which is limited to amaximum of12 ma. The input (pin2) ofoperational amplifier 3 is forcedto remain at ground potential by virtue of negative feedback. Anycurrent flowinginto the circuit is balanced by current leaving the inputthrough RL; therefore, the voltage of the output ofthe transresistanceamplifier is proportional to the input current which is the total currentthrough the electrochemical cell. The resultant output voltage foramplifier 3 follows the relationship: Vout = (Icdl)•RL. The output ofthe transresistance amplifier is inverted and scaled by the invertingamplifier 4.A double pole-double throw switch was added in the current monitorsection. The double pole-double throw switch selects one of twocircuit modes; current calibration or potentiostat operation. In thecurrent calibration mode, a known current passes through the 300 ohmprecision resistor to the current monitor circuit. A 5 kiloohm 10 turnpotentiometer is adjusted to give the correct voltage output to thecurrent display.Two digital panel meters are required tomonitor the reference voltageand the electrochemical cell current. The reference voltage was monitoredat the output of the buffer amplifier 1 and the total cell current wasmonitored at the output of amplifier 4.COMPUTER CONTROL FOR THE POTENTIOSTATA computer controlled digital-to-analog converter was added to thepotentiostat to provide greater flexibility. A 12-bit National Semi-conductor binary multiplying digital to analog converter DAC1222(DAC) was chosen to provide the conversions. The 12-bit DAC alloweda resolution of0.00244 volts per step over the chosen +5 to -5 voltagerange. Aninterface was constructed between the computer and the DAC,as shown in Fig. 2, which consisted of an address decode and variousdata latches to support the DAC.The interface between the computer and the DAC was designed sothat it could be used withother IBMcompatible computers. AnIBMXT-compatible was used in this laboratory. The DACinterface required±15 volts at approximately 20 ma and +5 volts at approximately 130ma. The ±15 volts were provided by the potentiostat power supplysection and the +5 volts were provided by the computer.Output voltage data were taken directly off the data bus and loadedinto two octal data latches (74LS373), one at a time. After bothlatches are loaded, a second pair of latches are pulsed and the voltagedata are transferred to the DAC for conversion. Care was taken toensure that the latches were in close proximity to the data bus. Smalldistances (less than one foot) will ensure clean, valid output voltagedata to the latches. The first pair of latches was used to change the8-bit data bus of the computer to 12-bits required by the DAC. Asecond set of latches was used in this design since the DAC did nothave an enable line for conversion initiation. Thus, the voltage data(all 12-bits) could be transferred to the DAC simultaneously permit-ting the DAC to convert the correct voltage data instead of two piecesof data. Two allow the 12-bit DAC bipolar voltage swings, a LF356JFET input OP-AMP was used (Fig. 2). Equations for the resistors are(National Semiconductor Corp., 1982):AV = Peak Voltage out / Voltage referenceR4 = (2 Av- 1) RRl = R2 (Av- 1) / AvR3 = Rl :: R2,where R ¦ 10,000 ohms, R2 = 2500 ohms, and the voltage reference= 2 volts.Potentiometers were used for the resistance values to allow finaladjustment of the DAC to eliminate any offsets caused by varyingcomponent tolerances. Resistor R2 was used to zero tolerance differencesfound in the linear op-amp while resistor R4 was used to adjust the± peak voltages in the design. Resistor R3 was found to be the mostcritical in allowed tolerances.Abasic program to control the potentiostat is included in Appendix 1.33Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10https://scholarworks.uark.edu/jaas/vol43/iss1/1034Proceedings Arkansas Academy of Science, Vol. 43, 1989A Versatile Potentiostat With Optional Computer ControlAPPLICATIONSThis design provides a versatile instrument which may be used fora wide range of electrochemical applications. It is the intent of theauthors to use the potentiostat as a teaching tool in a graduate levelcourse in electrochemistry. Inthis role the instrument willbe used toplate copper from solution, demonstrate electrolysis of solvents andionmigration, and generally familiarize students with the various aspectsof electrochemical systems.The current application of concern to the authors is the anodicoxidation of PCB's. Ithas been shown that PCB's may be oxidizedat a ruthenium dioxide anode (Laule et al., 1986). This initial successwith4.4'PCB has prompted work to optimize the reaction conditions.The reaction is carried out on a 5ppm solution of PCB in a 50/50 aceticacid/water solution. An oxidizing agent such as potassium persulfateis added and the solution subjected to a potential of 2.00 volts versusa silver/silver chloride reference electrode for 48 hours.The present work is an attempt to optimzie the yield ofthe reactionat room temperature. The variables of concern are: time of reaction,applied potential, oxidant used, and exposure to UVradiation. Initialresults indicate that the exposure of the reaction cell to UV light great-lyenhances the yieldof the reaction. Notenough data have been receivedto make any predictions as to the effect of other conditions on thereaction.APPENDIX 1after conversion voltage is in form"111111111111"low$ will take the right 8 bits for loading into latcheshighS will take the left four for loading into latcheslow$ = right$(bin$,8)high$-left$(bin$,4)convert low binary to decimal.conversion fo the lower 8 bits back to decimal for output tothe latches11 = 0 :bits = 1for x = 1 to 8shifts = right$(low$,x): shiftS = left$(shift$,l)ifshifts = "1" then 11 = 11 + bitsbits =bits*2next xprint "lowload ";11;convert high binary to decimalconversion of the high 4 bits into decimal for loading into thelatchesComputer Control for the Potentiostat 10-29-88'THIS PROGRAM WRITTEN FOR THE QUICKBASIC COM-'PILER. IT CAN BE MODIFIED TO FIT YOUR NEEDS.1) Voltage entered (+5 to -5 volts) and converted to positivevoltages only.2) Voltage is converted to its decimal equivalent voltage 0.0024414volts per step3) Voltage is converted to binary form"111111111111"4) The high four and low eight are converted back to decimal5) Voltage data loaded into the latches and transferred to DACstart:input"enter voltage ",voltvolt = volt + 5.00 :'changes the voltage to positive onlyvolt = cint (volt/.0024414)print "decimal convert volt ",voltconverts voltage to binaryx = 2048:bin$convert:voltl = (volt- x)if voltl >= 0 then bin $ = bin$ + "Vifvoltl < 0 then bin $ = bin$ + "0"if voltl >= 0 then volt = voltlx = x / 2ifx < 1 goto continuegoto convertcontinue:12 = 0 :bits = 1for x = 1 to 4shifts = right$(high$,x)shifts = left$(shift$,l)if shiftS = "1" then 12 = 12 + bitsbits = bits * 2next xprint "high load ";12the loading of the latches654 dec = 28E hex load latch one653 dec = 28D hex load latch two651 dec = 28B hex strobe data to datprint "loading the d / a ",qout 654.11out 653,12;'load one (1 );'load two ( 2 )print "output enabled",qout 651,0 ;'output enablegoto startendLITERATURE CITEDLAULE,G., R.M. HAWK, D. MILLER.1986. Oxidation of 4,4'-dicholorobiphenyl at a ruthenium dioxide anode. J. Electroanal.Chem., (213).NATIONALSEMICONDUCTOR CORP. 1982. Linear Databook.Santa Clara, CA.SKOOG, D.A. 1985. Principles of Instrumentation Analysis. ThirdEdition. Saunders College Publishing, New York, NY.34Journal of the Arkansas Academy of Science, Vol. 43 [1989], Art. 10Published by Arkansas Academy of Science, 1989

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Versatile Potentiostat with Optional Computer Control

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