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DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
Author’s full name
Date of birth
:
:
Title
: _________PORTABLE POTENTIOSTAT_______________
__________________________________________________
Academic Session
_________STEFFI MIT ANAK ANGIE ________________
___________3 SEPTEMBER 1988___________________
: _______________2010/2011_________________________
I declare that this thesis is classified as :
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(Contains confidential information under the Official Secret
Act 1972)*
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_______________________
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SIGNATURE
880903-13-5116
SIGNATURE OF SUPERVISOR
__
( NEW IC.NO/ PASSPORT NO)
Date : 9 MAY 2011
NOTES :
*
___
DR. LEOW PEI LING____
NAME OF SUPERVISOR
Date : 9 MAY 2011
If the thesis is CONFIDENTAL or RESTRICTED, please attach with the letter from
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― I hereby declare that I have read this thesis and in my opinion this
thesis is sufficient in terms of scope and quality for the
purpose of awarding a Bachelor‘s Degree of Electrical
Engineering (Control and Instrumentation ).‖
Signature
: …………………………….
Name of Supervisor
: DR. LEOW PEI LING
Date
: 9 MAY 2011
PORTABLE POTENTIOSTAT
STEFFI MIT ANAK ANGIE
This thesis is submitted in partial fulfilment
of the requirements for the award of the degree of
Bachelor of Engineering
(Electrical-Control and Instrumentation)
FACULTY OF ELECTRICAL ENGINEERING
UNIVERSITI TEKNOLOGI MALAYSIA
MAY 2011
―I declare that this thesis entitled ― PORTABLE POTENTIOSTAT ” is the results
of my own research except as cited the references.
The thesis has not been accepted for any degree and is not
concurrently candidate of any other degree.‖
Signature
:...........................................
Author‘s Name
:STEFFI MIT ANAK ANGIE
Date
:
9 MAY 2011
Dedication
Dedicated to my beloved parents Mr. Angie Anak Slat and his wife ,
And Mdm Riaw anak Ningkang and her husband.
Respectful sisters , Mdm Shirley Wride Anak Angie and her husband,
Mdm Ursula Umie Anak Angie and her husband,
Youngest Brother , Ezra Seran Anak Angie,
Thank you for the prayer,support and love
That you give me along in my journey
Not forgotten to my dearest one, Anthony Kasrul Anak Pulai
Who have always by myself during ups-and downs
Thank for everything.
Thank you for all lecturers in Department of Control and Instrumentation
Especially to my beloved supervisor , Dr. Leow Pei Ling ,
For the her continues support , encouraged, guidance, and inspired me throughout
my journey in education
Last but not least to my fellow friends SEI and GIFT ,
Thank for everything
ACKNOWLEDGEMENT
In the name of God the most gracious the most merciful.Thanks to Almighty
God for the gracious blessings that I finally completed my final year project entitled
potentiostat .First of all , I would also like to express my gratitude to all who had
helped and give me guidance during my time of completing this project.
I would like to express my gratitude and thanks to my supervisor, Dr.Leow
Pei Ling , Dr.Fauzan Che Harun and my labmate , Nor Baizura Mohd Noordin for all
the guidance ,idea and knowledge that their had given me throughout the year in
completing the project. My project would not be carried out smoothly without the
continuing support and encouragement given by lectures , course mates , and
technicians.
Finally the most important is my family .The continuous support they had
given to me throughout the four years study in Universiti Teknologi Malaysia (UTM)
had became my strength and motivation to completed my final year project .
Thank you.
ABSTRAK
Penggunaan instrumen kimia adalah peranti yang sangat umum untuk
mengukur di makmal. Terdapat
beberapa alat elektronik seperti potensiostat
digunakan untuk mengukur keluaran isyarat analog. Alatan instrument ini boleh
diklasifikasikan mengikut jumlah penggunaan voltan dan arus yang digunakan. Alat
pengukuran juga dapat diklasifikasikan mengikut kuantiti diukur dengan instrumen
serta prinsip operasi potensiostat. Projek ini merupakan skala berkadar kecil dimana
pembuatan terdiri daripada op amp yang akan digunakan sebagai pengikut voltan
dan penukar arus-voltan. Penggunaan GUI dapat membantu pengambilalihan data
dan sangat mudah untuk menganalisis data. Dalam projek ini, perisian LabVIEW
akan digunakan sebagai alat perhubungan antara peranti dan perisian. Perisian ini
juga dapat mengawal voltan yang akan dikendalikan melalui peranti National
Instrument. Keputusan yang diperolehi sangat berguna untuk memerhati aliran arus
dalam komponen bahan yang tidak diketahui bergantung kepada tindakan kimia
Redoks .
ABSTRACT
The use of chemical instrument is a very common devices to measure in the
laboratory . There are various electronic instruments such as potentiostat to measure
signal analog instruments. And even they are classified according to the utilization
of voltage and current used. Measuring instruments are classified according to both
the quantity measured by the instrument as well the principle of operation of
potentiostat. This project is a small scale design which consists of op amp that will
used as voltage follower and current- voltage converter . The used of GUI could
help data acquisition and direct easy to analyse the data . In this project, the
LabVIEW software will be use as the tool to perform as a driver. This National
Instruemnt driver will control the voltage to be operated through the interface card.
The results obtained are useful for the online monitoring of current flow in unknown
substance component depend on Redox reaction.
TABLE OF CONTENT
CHAPTER
TITLE
PAGES
TITLE
i
DECLARATION OF THESIS
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRAK
v
ABSTRACT
vi
TABLE OF CONTENT
vii
LIST OF FIGURES
x
LIST OF TABLES
xiii
LIST OF ABBREVIATIONS
xiv
LIST OF APPENDICES
xv
I
INTRODUCTION
1
1.1
Background Of Study
1
1.2
Objectives Of Project
2
1.3
Scopes Of Project
3
1.4
Report Outline
3
1.5
Summary Of Work
4
II
III
LITERATURE REVIEW
5
2.1
History of Potentiostat
5
2.2
Working Principle Of Potentiostat
6
2.3
Interfacing Method
8
2.4
Cyclic Voltammetry
10
2.5
Summary
13
RESEARCH METHODOLOGY
14
3.1
Introduction
14
3.2
Flow Chart of Methodology
14
3.3
Potentiostat Setup
15
3.4
Hardware Implementation
18
3.4.1 LM 741 Operational Amplifier
18
3.4.2 Potentiostat Circuit
20
3.4.3 Ag| AgCl Sensor Electrodes
21
3.4.4 National Instrument DAQ 6009
23
Software Implementation
27
3.5
3.5.1 National Instrument LabVIEW TM
8.2 Software
3.5.2 Graphical User Interface (GUI)
3.5.2.1 Cyclic Voltanmetry 1
27
28
28
for Verifying
Potentiostant Circuit
3.5.2.2 Function Generator Triangular
29
Voltage Waveform
3.5.2.3 Scan Data for Cyclic
Voltanmmetry
3.6
Summary
32
IV
EXPERIMENTAL SETUP
33
4.1
Introduction
33
4.2
Experiment Procedure
34
4.2.1 Consideration Prior to Beginning
34
Experiment
4.2.2 Instrument Start Up Procedure
35
4.2.3 Preparing the Instrument for
36
Measurement
4.2.4 General Steps for Making Measurement 36
4.3
V
VI
4.2.5 Data Handling
37
4.2.6 Instrument Shut – Down Procedure
37
Summary
37
RESULTS AND DISCUSSION
38
5.1
Introduction
38
5.2
Potentiostat Circuit Verification
39
5.3
Vitamin C
42
5.4
Glucose
46
5.5
Discussions
49
CONCLUSIONS & RECOMMENDATIONS
50
6.1
Introduction
50
6.2
Conclusions
51
6.3
Problems Happened During Project Accomplish 51
6.4
Recommendations For Further Project
52
REFERENCES
53
APPENDICES
55
LIST OF FIGURES
FIGURE
TITLE
PAGE
1.1
Gantt chart
4
2.1
i-E Curve Of Cyclic Voltammetry Measurements With
11
Varying Scan Rates
3.1
Flow Chart Project Design And Development
15
3.2
Setup For The Potentiostat System
16
3.3
Hardware And Software Interface
17
3.4
Feedback System Of Potentiostat
17
3.5
LM741 Op Amp
19
3.6
2 Op Amp Potentiostat Circuit Layout
20
3.7
2 Op Amp Potentiostat Circuit
20
3.8
Test Strip Electrode Consist Of A Platinum
22
Working Electrode, A Platinum Counter Electrode
And A Silver Reference Electrode.
3.9
Cable Connected For Test Strip Electrode To
Potentiostat Circuit
22
3.10
Crocodile Clip Attached From Cable Connected For
23
Test Strip Electrode
3.11
DAQmx Data Acquisition
24
3.12
National Instrument 6009 Device
24
3.13
National Instrument 6009 Device Block Diagram
25
3.14
Block Diagram For Verifying Potentiostat Circuit
28
3.15
Front Panel For Verifying Potentiostat Circuit
29
3.16
Block Diagram Triangular Voltage Generator
30
3.17
Front Panel Triangular Voltage Generator
30
3.18
Block Diagram Full Scan
31
3.19
Front Panel Full Scan
32
4.1
Photograph of experimental setup using
33
(a) DAQmx NI 6009 ,(b) potentiostat circuit ,
(c) electrode sensor and (d) Front Panel GUI 5.1
4.2
A Block Diagram Of Input And Output Of Cyclic
34
Voltammeter
4.3
Dummy Cell for Circuit Verification
35
5.
A Typical Voltage Waveform As Applied To A Cv Cell
39
5.2
i-t Curve Of Dummy Cell
40
5.3
i-t Curve Of Ascorbic Acid (Vitamin C ) Immersed
41
In Distillled Water.
5.4
V-t Curve For Vitamin C In Distilled Water
42
5.5
i-t Curve For Vitamin C In Distilled Water
43
5.6
i-E Curve For Cyclic Voltammetry Measurements
44
Vitamin C In Distillation Water Plotted Based
On The Data Collected. (V= 90mv)
5.7
Chemical Equation Redox Reaction Of Vitamin C
45
5.8
V-t Curve For Glucose In Distilled Water
46
5.9
i-t Curve For Glucose In Distilled Water
47
5.10
i-E curve for cyclic voltammetry measurements
48
glucose in distilled water plotted based on the data
collected. ( V=55mV redox potential)
LIST OF TABLES
FIGURE
TITLE
PAGE
3.1
Specification of op amp
18
3.2
Signal Description Pin connection of NI
25
LIST OF ABBREVIATIONS
A
-
Ampere
A
-
Electrode area
A/div
-
Ampere per Division
CE
-
Counter Electrode
C
-
Concentration of reactingspecies
D
-
Diffusion coefficient
DC
-
Direct Current
GCE
-
Grounded Counter Electrode‘
GUI
-
Graphical User Interface
ip
-
Peak current
I/O
-
Input/ Output
MΩ
-
Mega Ohm
mA
-
miliAmpere
mL
-
mili Litter
NI
-
National Instruments
n
-
Number of electrons involved
Op Amp
-
Operational Amplifier
PC
-
Personal Computer
RE
-
Reference Electrode
V
-
Volt
v
-
Scan rate
VI
-
Virtual Instrument
WE
-
Working Electrode
USB
-
Universal Serial Buses
LIST OF APPENDICES
APPENDIX
A
TITLE
i-E for cyclic voltammetry measurements
PAGE
55
vitamin C in distilled water
B
i-E for cyclic voltammetry measurements
56
glucose in distilled water
C
User Guide And Specifications USB 6008/6009
57
CHAPTER 1
INTRODUCTION
1.1
Background of Study
There are a lot of studies that have been done in order to improve potentiostat
design to allow better performance in electrochemical reactions data acquisition. In
this century, this method has been widely used in industry laboratories especially in
physical ,chemistry and biology (Jin, Wang et al. 2009).
Potentiostat are routinely researching the study of electrochemical system in
particular item from the crucial measurement instrument component of
electrochemical reaction based on detection system for chemical, physical and
biological sensor.
Development of detection system in process automation
chemical
industries(Jin, Wang et al. 2009), industrial electrochemical instruments are needed
to obtain specific static characteristics such as accuracy, precision and sensitivity; in
which this instrument will be used for standard industrial communication
protocols(Jin, Wang et al. 2009).
In operation, potentiostat is an electronic instrument used for controlling a
three plate electrode cells consists of a working electrode, a counter electrode and a
reference electrode. This instrument is mostly used in electroanalytical experiments.
The main function of the system is to maintain the potential voltage of working
electrode at constant level based on the reference electrode by adjusting the current
flow at auxiliary electrode.
The design of the device consists of an electric circuit which is usually
described in terms of simple operational amplifiers (op –amp). There are a variety of
potentiostat models for application in various fields. Potentiostat is widely used in
electroanalytical techniques to identify , quantify and characterize Redox
potential(Yarnitzky 2000) .Furthermore this device is recently used to measure
species such as inorganic , organic, and biochemical . (Gopinath et al, 2004)
1.2
Objectives of Project
The main cores of this project are:
i. To design the electronics circuit for potentiostat by using op-amps for
general laboratory measurement in electrochemistry.
ii. To enable obtaining real time data acquisition using computer that
communicate through Universal Series Bus (USB).
iii. To develop Graphical User Interface (GUI) for potentiostatic control and
to allow the interaction with potentiostat.
1.3
Scopes of Project
The scopes of the project include a review of:
i. Design the electronic circuit for potentiostat
ii. Build the Graphical User Interface (GUI) using NI Lab VIEW for
measurement of data acquisition and display.
iii. Both the circuitry and virtual instrument controlled unit are connected to
create bi-communicate between hardware and the software.
1.4
Report Outline
This thesis consists of five chapters. In the first chapter, it discusses the
objective and the scope of this project as well as the summary of works. Chapter 2
discusses more on the theory and literature reviews regarding the research and
development of potentiostat. In Chapter 3, the discussion is on the methodology for
hardware and software implementation of this project.
In Chapter 4, an experimental setup is explained and discussed. The result
and discussion of this project are presented in Chapter 5. Last but not least, Chapter 6
discusses the conclusion of this project; problems arise during the project
accomplishment and recommendation for future work.
1.5
Summary of work
Implementation and works of the project are summarized into the flow chart
as shown in Figure 1 .1 Gantt charts.
No.
1
Activity
July Aug Sep Oct Nov Dec
Literature
review
Design
2
circuit with
MultiSIM
software
Develop
Graphical
User
3
Interface
(GUI) for
potentiostatic
control
Enable
obtaining
4
real time
data
acquisition
5
6
7
Data analysis
Data
verification
Report
Figure 1.1 Gantt charts
Jan
Feb
Mar Apr May
CHAPTER 2
LITERATURE REVIEW
2.1
History of Potentiostat
For over 60 years, a number of successful potentiostat designs have been
renewed and implemented using different technique. In 1942, A. Hickling invented
the idea of automatic system to control the working electrode of potentiostat and this
electronic device was successfully created and named as potentiostat. (Hickling
1961).
Researchers have accentuated
high precision, stable, rugged and even
smaller design of potentiostats that even can be used for on-site measurement
(Gopinath et al, 2004) in various fields.
2.2
Working principle of potentiostat
Basically, the working principle of potentiostat is to control the potential
voltage difference between a working electrode (WE) and reference electrode (RE)
and these two sensors are the basic components of electrochemical sensor. While the
potentiostat controls the electrochemical reaction, another function of counter
electrode (CE) is to act as the medium of injecting currents into the sensor.
Combinations of these two definitions showed that the potentiostat has two
tasks. Initially, the working principle of potentiostat is to measure the potential
difference between the working electrode (WE) and the reference electrode (RE)
without polarizing the reference electrode and then the process proceed by
comparing the potential difference with a present of voltage using op - amp.
Secondly, it injects current flowing from counter electrode (CE) to a working
electrode (WE) in order to neutralize the difference between the present voltage and
the existing working electrode (WE) potential.
The controlled variable in the potentiostat is the sensor preset voltage. Such
an approach of the two task of potentiostat is usually used to measure the
amperometric (Huang, Syu et al. 2007) that is relating to a chemical titration in
which the measure the capacity of the electric current flowing under an applied
potential difference between two electrodes. Hence, this measurement can be also
used to measure the solution to detect the end point of signal applied.
All potentiostats that have been invent and operate successfully on the same
general principle in that the potential difference between the working electrode and a
suitable reference electrode is continually compared with a voltage originally from a
potentiometer (Hickling 1961) .
Working principle of ammeter and voltmeter related to potentiostat by
combined them in single device. According to (A.T.K 1973) , potentiostat is most
important instrument device and in apart from the ammeters and voltmeters which
are working just likes ―eyes and ears‖.
An ideal general use of devices inside laboratories should be sensitive to the
changes such as potential shift in the range voltage varying 0.01 V or less . In the
same time it should be capable in controlling currents varying 10
-6
to at least 10 A
(Hickling 1961) . Basically, the voltage to be control by potentiostat need require
adjustment other that setting the potentiometer current.
The potential inside the solution as sensed by reference electrode (RE) is
compared and analyze with applied differential of voltage potential by mean of an
operational amplifier (Hickling 1961) which allow a counter electrode(RE) to a
potential required for maintaining the applied potential at point of contact at
reference electrode with the chemical solution . (Yarnitzky 2000).
From the previous paper of Hickling and Yarnitzky, comparing between
potential of solution and applied potential is depend in several potentiostat
configuration have been proposed.
From the design of potentiostat circuitry done by both researchers , different
potentiostatic circuits and current measuring devices can be designed and can be
improved using different circuit based on what chemical solution might been tested .
(WM.Schearz et al 1963).
Previous author, Chaim N. Yarnitzy used ‗Grounded Counter Electrode‘
(GCE) potentiostat address all problems where the potential inside the solution
contiguous to the surface of the working electrode (WE) can‘t be controlled directly
by a common counter electrode (CE) due to the sensitivity of counter electrode (CE).
By using GCE potentiostat, it allows simple potential control of any working
electrode (WE)versus a reference electrode (RE) located behind it .
GCE potentiostat much more complicated when a reference electrode (RE)
comprises every working electrode is employed .To prevent this problem reference
electrode will be grounded and this connection will more easy to connect to other
instruments or a computer.
2.3
Interfacing method
Bus power data acquisition for USB using NI LabVIEW is one of the
medium to interface between hardware and software and enable to obtain real time
data acquisition to communicate with potentiostat through USB. It is low cost device
and bus- powered NI data acquisition products to feature high performance
multifunction in different circuits.
NI M Series capable function without external power supply and allows
high-speed data streaming across the USB cables to the PC. Data acquisition that
obtains using LabVIEW is the process of sampling of real world physical conditions
and conversion of the resulting samples into digital numeric values that can be
manipulated by a computer.
Serial data interface has been reported in literature with specific example
using RS232 serial data transfer interface (Huang, Syu et al. 2007) were they
managed to construct a portable potentiostat as specific sensor for detect bilirubin.
Another serial data interface has been reported in (Sheu and Huang 2007) which
again features the use of EZ-USB , the PC Driver as general purposes is applied .
The GPD is a general use device driver suitable for interfacing method
between PCs and an EZ-USB- based on peripheral. In the same time it is providing
a user mode as a medium interfacing for common USB device requests and data
transfer.
Another paper has been published with example QuickBASIC software
environment (Fang, McGrath et al. 1995).This design is based on the usage of
common reference and counter electrodes to decrease the complex of the electrode
arrangement.. Fang, McGrath et al. create software for instrument controlled such as
data display in the 3 D formats. This the same time this device can be run on-line
and post-run data processing to analyze.
The storage has been developed to keep the data using the QuickBASIC
software environment.
By using data display in 3 Dimension (3-D), user can
interface use a Windows style display. This instrument is easy to control
and
achieve user friendliness with an on-line help facility. This method data is stored in
a spreadsheet compatible format (ASCII with ‗0‖ column delimiter) to facilitate postrun processing with standard applications packages such as Microsoft EXCEL.(Fang,
McGrath et al. 1995) .
(Kounaves and Lu 1992) used original Microsoft QuickBASIC software. For
more faster operation and easier to portable to PC, this programmed was recently
also rewritten in Microsoft QuickC.
By using of this software, programmed can easily be modified to provide
platform to create an user-friendly control of the PAR 273 potentiostat for more than
one PC can controlling the electrochemical experiments to require display of 3-D
or 2-D data signal. They combined a technique required the faster data acquisition of
electrochemical data through a specific computer control the potentiostat .The realtime display for data acquisition can be obtain .
Directly for the data, the programmed could process electrochemical
experiment. The form of result present in a 3-D of chromatovoltammographic data
using an IBM PS/2 and PAR model 273 potentiostat.
2.4
Cyclic voltammetry
Currently the electronic instrumentation now day available are commercial
devices. Most of the potentiostat devices are expensive. Trends to commercialize the
electrochemical instrumentation toward multifunctional device generally limit very
rapid . Hence, it is preferable to use a specific designed instrument which avoids the
problem in multipurpose use . (Cummings, Jensen et al. 1978).
A potentiostat is widely used for a research in electroanalytical techniques
including cyclic voltammetry. In cyclic voltammetry, the potentiostat apply the
working electrode a certain
voltage which rapidly changes linearly with time
.(Cummings, Jensen et al. 1978).
Figure 2.1 show the scan rate of cyclic voltammetry measurement. An anode
and cathode peak curve show the potential is defined by the activities of Redox at the
electrode surface where the depletion have taken place.
Figure 2.1: i-E curve of cyclic voltammetry measurements with varying scan rates
Consider an electrochemical reaction at an electrode works as sensor,
conventionally it written as reduction (Basil H. Vassoset al 1993) :
(Ox)work + n e-
(Red )work
(1)
When the solution component is electrolyzed means oxidized and reduced
process happened in the same time by placing the chemical solution in contact with
electrodes. As the result, this process making the surface sufficiently positive or
negative.
The current are given depends in the initial voltage, the scan tare and the time
can be analyzed in detail. (R.N Adams et al 1969). A important parameter is the
peak current given by the equation (R.S.Nicholson et al 1964) :
ip = (Const) n 2/3 A D ½ C v ½
ip = Peak current
n = Number of electrons involved
A = Electrode area
D = Diffusion coefficient
C= Concentration of reacting species
v = Scan rate
(2)
2.5
Summary
Summary of work for this chapter is to explain more the past work that had
done by other researchers. Different scope that had been done in term of interfacing
method. Although the interfacing method was different, but the working principle of
potentiostat remain the same.
In cyclic voltammetry measurement with different scan rates, the results from
peak current can be analyzed and the values of peak current depend on component
inside the solution.
CHAPTER 3
RESEARCH METHODOLOGY
3.1
Introduction
In this chapter will discuss about the procedures and the techniques used
along this project. Besides that, experiment set-up and the major equipment for data
interface are also described
3.2
Flow Chart of Methodology
Figure 3.1 shows the flow chart of progress of final year project . Its shows
the step needed to complete this research.
Start
Literature Review
Hardware Design
Software Design
Hardware Iimplementation
NO
NO
Satisfy
Analysis
Finish
Figure 3.1 : Flow chart project design and development
3.3
Potentiostat Setup
The function of cyclic voltammetric techniques is to analyze electro-chemical
active Redox chemical species. There are two interfaces processes happened .The
first interfaces is used to apply the triangular voltage waveform from function
generator to the electrochemical cell .The second interface is used to apply analyze
the current through the electrochemical cell.
The block diagram of the potentiostat set-up is presented in Figure 3.2. A
personal computer with an acquisition board (National Instruments 6009) is used to
control the voltages applied to the electrochemical cell and to measure the current
flowing through the cell. Another function accomplished is the digital control of the
output and input scale.
Figure 3.2 : Setup for the potentiostat system
Figure 3.3 shows the picture of the project. The project is divides into two
parts that are software and hardware implementation. Each part of the project will
discuss in the following section. The op-amp circuitry provides the interface between
the NI LabVIEW and sensor electrodes.
Figure 3.3: Hardware and Software Interface
Controller
Sensor
Final Element
Process
Outputs
Inputs
Figure 3.4 : Feedback system of Potentiostat
Figure 3.4 shows the feedback system of potentiostat for the control system
and appear into three basic elements. Input of the system is triangular voltage while
the output of the potentiostat system is current. An Ag|AgCl electrode reacts as
sensor. Control panel in graphical user interface (GUI) react as controller of the
system. Overall for the system is LabVIEW software which control based on the real
time. Final element to obtain measurement element is cyclic voltammetry.
Both the circuitry and virtual instrument such as power supply, function
generator and oscilloscope can be control in one system and connected to create bicommunicate between hardware and the software
3.4
Hardware Implementation
This section will discuss about components that had been used included,
LM741 operational amplifier, test strip electrode sensor and National Instrument
6009.
3.4.1 LM 741 Operational Amplifier
The LM741 series are general purpose operational amplifiers which feature
improved performance over industry standards like the LM709. They are direct,
plugin replacements for the 709C, LM201, MC1439 and 748 in most applications.
The amplifiers offer many features which make their application nearly
foolproof overload protection on the input and output, no latch-up when the common
mode range is exceeded, as well as freedom from oscillations. The LM741C is
identical to the LM741/LM741A except that the LM741C has their performance
guaranteed over a 0°C to +70°C temperature range, instead of −55°C to +125°C.
Cyclic voltammetry requires two simple operational amplifier (op amp)
circuits. This potentiostat construct by using inexpensive and robust LM741
operational amplifier chips. A pin diagram of the 741 chip is shown below. Figure
3.3 is the standard triangle notation for each op amp has connections corresponding
to the pins 2 and pin 3 as an inputs while pin 6 as an output. . A ±15 V power supply
not shown in Figure 3.4 must supply -15 V to pin 4 while +15 V to pin 7 on each 741
chip. The specification of the op amp is shown in Table 3.1
Figure 3.5 : LM741 Op Amp
Table 3.1 : Specification of the Op Amp
Manufacturer
National Semiconductor
Input Voltage
15V
Power Dissipation
500mW
Type
LM741
3.4.2 Potentiostat Circuit
V CC
VEE
5V
7
AO1 +
1
5
U1
3
6
AE
2
AO1 -
LM741CH
4
4
AI1 -
U2
2
AI1 +
RE
WE
6
3
5
1
7
LM741CH
R1
National Instrument 6009 Device
51k Ω
C1
47µF
Figure 3.6 : 2 Op Amp potentiostat circuit layout
Based on Table 3.2 , AO1 + , AO1- , AI1 + and AI- will be connected on
DAQmx device. VCC will be connected to +5 V pin power supply on DAQmx. VEE
will be connected to Ground pin.
Figure 3.7 : 2 Op Amp potentiostat circuit
0V
Figure 3.6 show the design layout of two op amp circuits required for the
cyclic voltammetry experiment. Figure 3.7 show the potentiostat circuit on PCB
board.
3.4.3 Ag|AgCl Sensor Electrodes
The surfaces of working electrode are the platform where the electrode
transfer electron occurs. The counter electrode is usually a sacrificial electrode that
purely serves to complete the circuit. The surface area of counter platinum electrode
is larger compared to the platinum-working electrode so as to avoid the current limit
at the working electrode by the counter electrode
Figure 3.8 show the Ag|AgCl sensor electrodes will react directly sensor
because it is invasive contact with chemical reaction.
The reference electrode is
used to produce a constant potential in the electrochemical cell. In high precision, the
production of potential energy will against the other potentials and the value may be
determined.
Electrodes are static and sit in unstirred solutions during cyclic voltammetry.
The rate of electron transfer at the surface of the electrode can be related to the
electrochemical activity of the chemical species concentration levels and diffusion
rates. It is good to note that the transfer of charge occurs only at the surface of the
electrode and only if the molecules are present near the surface.
Figure 3.8 : Test strip electrode consist of a platinum working electrode, a platinum
counter electrode and a silver reference electrode.
Figure 3.9 : Cable connected for test strip electrode to potentiostat circuit.
Figure 3.9 and Figure 3.10 show the cable connections between potentiostat
circuit and electrode.
Figure 3.10: Crocodile clip attached from cable connected for test strip electrode
Before begin the experiment, make sure the test strip connection is clean from
any dust. The crocodile clip will attach to WE, CE and RE based on pin on
potentiostat circuitry. The usage of this cable, crocodile clip and electrode will be
discussed on Chapter 4, experimental setup.
3.4.4 National Instrument DAQ 6009
NI DAQ driver sustain the connection between LabVIEW software and NI
data acquisition. It is used to communicate with potentiostat circuitry .Figure 3.11
show list of data acquisition icons that can obtained from functions palette for
DAQmx.
Different kind of function can be obtain and each routine corresponds to a
programmatic operation such as configuring, reading from, writing to, and triggering
the instrument. Figure 3.12 show a instrument driver NI 6009 d is a part of system
which use for bi-communicate between hardware and the software routines that
control a programmable instrument.
Figure 3.11 : DAQmx data acquisition
Figure 3.12: National Instrument 6009 Device
The following block diagram shows on Figure 3.13 as key functional
components of the USB-6008/6009.
Figure 3.13: National Instrument 6009 device block diagram
The following table is the single available on the pin connection of NI 6009
for potentiostat circuit.
Table 3.2 : Signal description pin connection of National Instrument 6009
Signal
Reference
Direction
Description
Name
GND
Ground—The reference point for the single-ended AI
measurements, bias
current return point for differential mode
measurements, AO voltages, digital signals at the I/O
connector, +5 VDC supply, and the +2.5 VDC
reference
AI <0.7>
Varies
Input
Analog Input Channels 0 to 7—For single-ended
measurements, each signal is an analog input voltage
channel. For differential measurements, AI 0 and AI 4
are the positive and negative inputs of
differential analog input channel 0.
The following signal pairs also form differential input
channels:
<AI 1, AI 5>, <AI 2, AI 6>, and
<AI 3,AI 7>
AO 0
GND
Output
Analog Channel 0 Output—Supplies the voltage
output of AO channel 0.
AO 1
GND
Output
Analog Channel 1 Output—Supplies the voltage
output of AO channel 1.
+5 V
GND
Output
+5 V Power Source—Provides +5 V power up to 200
mA.
This is list of pin connection use in potentiostat circuit . The power supply
+5V can be supply directly from DAQmx . The connection of every pin must be
firm. Further references using NI6009 DAQmx can be refer to Appendix C .
3.5
Software Implementation
For software implementation, LabVIEW is used to controller in graphical
assembly language. Besides, MultiSIM is used for preliminary circuits design to
create potentiostat.
3.5.1 National Instrument LabVIEW TM 8.2 Software
NI LabVIEW software has a ability to connect and interact with potentiostat.
By using LabVIEW software, it can control the driving voltage and to measure the
output current response The third party instrument that is potentiostat make easy an
acquiring data. The instrument drivers can make instrument straight forward to
control . The use of LabVIEW can eliminate the need to learn the programming
protocol because this software is graphical computer language to interact between
hardware and software.
The front panel is built by inserting the appropriate controls and indicators in
a drag-and-drop manner on the front panel frame, the block diagram, i.e. the part of
the VI in which the actual programming is carried out. The LabVIEW programs runs
based on cyclic voltammetry by using application of triangular voltage potential time
waveform from the one output channel and data collects from the resulting current
response of the system through a current to voltage. It uses an I/O device such as an
NI USB-6009 to generate a triangular waveform output which is applied to the
external input of the potentiostat.
3.5.2 Graphical User Interface (GUI)
A LabVIEW software consists of two main parts which is a block diagram
and a graphical user interface (GUI).
3.5.2.1 Cyclic Voltanmetry 1 for Verifying Potentiostant Circuit
A block diagram for Figure 3.14 is a window where the code is developed.
Whereas the front panel in Figure 3.15 is a GUI that allows user to customize it with
objects like graphs, and control the sample and amplitude.
Figure 3.14 : Block diagram for verifying potentiostat circuit
Figure 3.15: Front panel for verifying potentiostat circuit
3.5.2.2 Function Generator Triangular Voltage Waveform
Function generator for triangular voltage waveform si the most important part
in this program.
A block diagram in Figure 3.16 is a window where the function generator of
triangular voltage wavefrom . Whereas the front panel in Figure 3.15 is a window
that require to control the number of sample ,amplitude, switching 1 and 2 , intial and
final potential and scan rate
The data of input and output wavefrom can be
customize on the graph based on Figure 3.17.
This triangular waveform will plug in analog input AI 1 at DAQmx. These
are passed through the program An advanced user could modify this VI to make
more than one cycle possible, and to incorporate separate initial and final potentials.
Figure 3.16 :Block diagram triangular voltage generator
Figure 3.17 :Front panel triangular voltage generator
3.5.2.3 Scan Data for Cyclic Voltanmmetry
A block diagram in Figure 3.18 is a scan data for cyclic voltanmetry where
the function generator of triangular voltage wavefrom at AI 1 and output current
obtain AO.
The front panel in Figure 3.19 is a window that require to control the number
of sample ,amplitude, switching 1 and 2 , intial and final potential and scan rate.
The data of input and output wavefrom can be customize on the graph based on
Figure 3.17. The data collected and plotted on graph.
Figure 3.18:Block diagram full scan
Figure 3.19 :Front panel full scan
3.6
Summary
Summary of work for this chapter is to discussed more in methodology
especially in devices and equipments that had been selected and will be use for
experimental setup to obtain data. Next chapter will be explained more how this
experiment will be conducted.
CHAPTER 4
EXPERIMENTAL SETUP
4.1
Introduction
In this chapter, experimental setup will be discussed especially how the
potentiostat circuit , NI 6009 DAQmx , electrode sensor connection and software
setup to obtain the data acquisition.The experimental setup is illustrated in Figure
4.1.
(a)DAQmx
6009 NI
(b)Potentiostat
Circuit
(d)Front
Panel GUI
(c)Electrode Sensor
Figure 4.1 : Photograph of experimental setup using (a) DAQmx NI 6009 (b)
potentiostat circuit , (c) electrode sensor and (d) Front Panel GUI
W
R
C
Input
Electrodes
Output
Figure 4.2 : A block diagram of input and output of cyclic voltammeter
4.2
Experiment Procedure
In this section extra information about cyclic voltammetry process and the
voltage monitoring experimental setup is presented.
4.2.1 Considerations Prior to Beginning Experiment

Cyclic voltammetry requires the use of a working (gold), reference (often
Ag|AgCl) and counter (platinum) electrodes. Be sure to use the
appropriate electrode materials in experiment.

Experiments are generally run in solutions that is maintained using a
supporting electrolyte.

Prepare the dummy cell show on Figure 4.3 which is use for circuit
verfication.

Prepare the 20ml of vitamic C and glucose for next step of experiment.
Both solution is carefully prepared separately by using different cup.
R1
R2
R3
10k Ω
10k Ω
10k Ω
C1
4.7µF
Working Electrode
Counter Electrode
Reference Electrode
Figure 4.3 : Dummy cell for circuit verfication
Based on Figure 4.3, potentiostat was tested with a resistor–capacitor dummy
cell connected to its outlets. The verification of circuit use combination on series
resistor- capacitor because it can create similar wave with the output response i-E.
4.2.2
Instrument Start-up Procedure

Ensure that the DAQmx plugged in to a USB port on the
computer.DAQmx NI 6009 run through Measurement and Automation
Software to verify the Analog Out (AO) and Analog Input (AI) which
one is used for measurement.

Before begin an experiment on Vitamin C and Glucose, potentiostat will
be test on dummy cell with consist of series of capacitor and resistors.

Once the response on dummy cell satisfied the output response , the real
experiment on vitamin C and glucose will be proceed.
4.2.3
Preparing the Instrument for a Measurement

The test strip electrode place at the end of cable carefully to obtain
good result and reduce any movement of electrode during the
experiment begin.

All connection between DAQmx and wires from potentiostat must be
tied . Make sure no short circuit happened .
4.2.4
General Steps for Making a Measurement

To prepare the instrument for a specific experiment it will be
necessary to adjust the control the number of sample ,amplitude,
switching 1 and 2 , intial and final potential and scan rate.

Once all values have been set, click on Run to continue. The most
common values that are changed are:
I.
The intial and final potential setting determines the starting
potential for the waveform.
II.
The scan rate setting determines the scan rate for the
voltammogram.
III.
The Switching 1 and 2
setting determines the maximum
positive and negative potentials thatthe potentiostat can
produce. A setting of 1V or 2V is typical.
4.2.5 Data Handling
4.2.6

Saving data using File - Save of File – Save As command.

Peak potential and peak current can be determine using the cursor.

The data will be plotting using Mircosoft Excel.
Instrument Shut-Down Procedure

Be sure that all electrodes have been disconnected and power the
instrument off.
4.3
Summary
Summary of work for this chapter is to explain more in produces of
experiment and precaution during the experiment conduct.
Summary of work for this chapter is to discussed more in methodology
especially in devices and equipments that had been selected and will be use for
experimental setup to obtain data. Next chapter will be explained more how this
experiment will be conducted.
CHAPTER 5
RESULT AND DISSCUSSION
5.1
Introduction
In this section, the experiments conducted to measure the redox activites such
as dummy cell , vitamin C and glucose using potentiostat system with the results and
discussions are presented.
The potentiostat testing was carried out by applying cyclic voltammetric
technique on two type of solution had been measured : ascorbic acid and glucose.
An electrode sensor was tested with ascorbic acid and glucose immersed inside
distilled water. The solutions were tested at 1 mV /s (volts/second) scan rate and the
triangular voltage was varied between + 1.5V and 0 V.
The triangular voltage waveform applied between the reference and working
electrode is updated and the current readings are taken every time the voltage is
updated. Figure 5.1 show the input of triangular waveform when amplitude of
voltage is 1 V and number of sample is 64.
Figure 5.1 : A typical voltage waveform as applied to a CV cell
5.2
Potentiostat circuit verification
The potentiostat testing was carried out by applying cyclic voltammetric
technique on various type of testing example.
The design of in LabVIEW had been tested for the early stage of experiment
to verify the potentiostat circuit either the device works or not. The verification of
potentiostat goes using dummy cell . Dummy cell contained 10 M Ω resistor .
Figure 5.2 show the triangular wave current versus time for dummy cell. As
the result , the potentiostat work according to triangular wave It is a good idea to use
a resistor as a dummy cell to test the performance of the potentiostat to make sure it
doesn‘t distort data at high scan rates.
The working electrode lead can be attached to one end of the resistor, and the
counter electrode and the reference electrode are both attached to the other end of the
resistor.Good data will be straight lines which follow Ohm‘s Law.
.
Figure 5.2 : i-t curve of dummy cell
.
Experiment proceed for the measurement Vitamin C and glucose in distilled
water . Figure 5.3 show the output current versus time for vitamin C once it
immersed into distilled water . After the measurement system was properly checked
and tested, it was used for sensor measuring by the cyclic voltampere method
Figure 5.3 :i-t curve of ascorbic acid (Vitamin C ) immersed in distillled water.
5.3
Vitamin C
Figure 5.4 shows the graph of half cycle voltage applied to potentiostat versus time
.
Graph voltage versus time
140
Voltage(mV)
120
100
80
60
40
20
0
0
5
10
15
20
25
30
Time(s)
Figure 5.4 : V-t curve for vitamin C in distilled water
From the graph it can be observed that the half cycle of triangular voltage
form versus time.The peak of the voltage is 120 mV. Peak time is 25 s.
Graph current versus time
250
Current(µA)
200
150
100
50
0
0
5
10
15
20
25
30
Time(s)
Figure 5.5: i-t curve for vitamin C in distilled water
From the graph it can be observed that the output of current curve versus
time.The peak of the value of current is 235 µA when time of electron release is 18
s.
Graph current versus voltage
250
Current( µA)
200
150
Anode Slope
100
Cathode Slope
50
0
0
-50
50
100
150
Voltage (mV)
Figure 5.6 : i- E curve for cyclic voltammetry measurements vitamin C in
distillation water plotted based on the data collected. (V= 90mV)
Figure 5.6
shows the i-E curve
for cyclic voltammetry measurements
vitamin C in distillation water plotted based on the data collected. Figure 5.6 shows
the voltammogram of 10 mM ascorbic acid in a distilled water .
In this experiment, the scan starts at 0.00 mV (blue) and the working
electrode voltage is then increased to + 120 mV. A strong maximum at 90 mV
indicates oxidation to dehydroascorbic acid. There the very weak peak at about 95
mV on the red curve shows may be due to the instability of dehydroascorbic acid .
Dehydroascorbic acid is not reversible, therefore the smaller peak noticed at
about +95 mV on the red curve shows may due to the instability of dehydroascorbic
acid and slow kinetics of the reverse half-reaction. (Kissinger et al 1983)
The formula for ascorbic acid is C6H8O6 and the structures for the reduced
form and for the oxidized form (dehydroascorbic acid) are shown below:
Figure 5.7 : Chemical equation redox reaction of vitamin C
5.4
Glucose
V- t For Glucose in Distilled Water
120
Voltage (mV)
100
80
60
40
20
0
0
5
10
15
20
25
Time (s)
Figure 5.8: V-t curve for glucose in distilled water
From the graph it can be observed that the half cycle of triangular voltage
form versus time.The peak of the voltage is 100 mV. Peak time is 21 s.
i-t For Glucose in Distilled Water
0.003
Current (µA)
0.0025
0.002
0.0015
0.001
0.0005
0
0
5
10
15
20
25
Time (s)
Figure 5.9: i-t curve for glucose in distilled water
From the graph it can be observed that the output of current curve versus
time.The peak of the value of current is 0.0025 µA when time of electron release is
13 s.
i-E Curve for Glucose in Distilled Water
0.003
Current(µA)
0.0025
0.002
0.0015
Anode Slope
0.001
Cathode Slope
0.0005
0
0
50
100
150
Voltage (mV)
Figure 5.10: i-E curve for cyclic voltammetry measurements glucose in distilled
water plotted based on the data collected. ( V=55mV redox potential)
Figure 5.10 shows the i-E curve for cyclic voltammetry measurements
glucose in distillation water plotted based on the data collected. Figure 5.10 shows
the voltammogram of 10 mM glucose in distilled water . It is can be known that a
glucose can be easily oxidized when it immersed in the distilled water.
In this experiment, the scan starts at 0.00 mV (blue) and the working
electrode voltage is then increased to 105 mV. A strong maximum value at 55mV
showed as an indicate oxidation activities for glucose. There the no weak peak at
cathode slope on the red curve because it may be due to the inrevesible of glucose .
From the glucose‘s result , it gives approximately straight lines because it
might decompose before the reduction cycle can convert it back. (B.H. Vassos et al
1993).
5.5
Discussions
From the result of vitamin C and glucose, the experiment can be discussed
due to several aspects.
In chemical terms this charge transfer is either oxidation or reduction of the
species. Anode slope with blue colour shows oxidation process of the species means
that electrons are lost from the molecule . While cathode slope with red colour shows
reduction process means that the molecule gains electrons.Two peaks are not equal
height , the substance show was not reversibility .
Based on literature review a several important parameter such as number of
electrons involved in an equation given (R.S.Nicholson et al 1964) when peak
current had been obtain and directly can be solved using equation such as detection
on how much concentration of reaction species reacted in solution.
CHAPTER 6
CONCLUSIONS & RECOMMENDATIONS
6.1
Introduction
This project has been completed by using LabVIEW 8.2 as a data acquisition
to obtain and reconstruction X-Y graph to analyze the project. The main objectives
of the project is achieved effectively. Although there were some diffculty but mostly
it was due to lack of information about the chemical components and facilities to do
the laboratory experiement .
This chapter summarizes all the achievement of the project. This chapter also
includes the problem happened during the project accomplish
recommendations for this project.
and future
6.2
Conclusions
The first objective is successfully done. An electronics circuit for portable
potentiostat by using op amps for laboratory measurement in electrochemistry had
been designed .
Besides that, the second objective is also successfully done . Real time data
acquisition using computer that communicate through Universal Series Bus (USB)
had been designed . . The interface was successfully built between the computer and
electrode sensor by using the USB 6009 as a medium to connect between hardware
and software .
The third objective of the project successfully .A Flexible Graphical User
Interface (GUI) for potentiostatic control and allow to interact with potentiostat had
been developed . For this matter , the input of system can easy change through the
modifying control panel of software .
6.3
Problems happened during project accomplish
Due to time constrain, the potentiostat can‘t be measured using chemical
solution such as Ferri Cyanide because of safety and pre caution reason .
However the most difficult part of the project was the actual programming
especially to scan the measurement to obtain data i-E curve. The X-Y graph need to
redo by plotted again using Microsoft Excel to obtain better result. From here the
analyzing data could be done.
Limit of time to design the software because a lot of unknown application
control panel and it is need time to explore and understand .
6.4
Recommendations for further project
The following can be done to improve the work further in future:

Potentiostat can be create in a multichannel where as combination of
working electrode by using single reference , auxiliary electrode and
an array of working electrodes.

Applying cyclic voltammetric on various concentration of chemical
solution

Using other analytical procedures such as pulse waveform can obtain
different kind of data analyze .

Improving the circuit performance by adding filter component.

Further study on the application of LabVIEW software is needed to
gain more benefits from this software since it has many valuable
functions that can be used. High understanding using LabVIEW can
reduce time in design software for data acquisition.
REFERENCES
A.T.K (1973). "The potentiostat and its applications : J.H. von Fraunhofer and C.H.
Banks, Butterworths, London, 1972, pp. vi + 254, price £6.00." Journal of
Molecular Structure 17(2): 446-447.
Cummings, T. E., M. A. Jensen, et al. (1978). "Construction, operation and
evaluation of a rapid-response potentiostat." Electrochimica Acta 23(11):
1173-1184.
Fang, T., M. McGrath, et al. (1995). "Development of a computer controlled
multichannel potentiostat for applications with flowing solution analysis."
Analytica Chimica Acta 305(1-3): 347-358.
Hickling, A. (1961). "A simple potentiostat for general laboratory use."
Electrochimica Acta 5(3): 161-168.
Huang, C.-Y., M.-J. Syu, et al. (2007). "A portable potentiostat for the bilirubinspecific sensor prepared from molecular imprinting." Biosensors and
Bioelectronics 22(8): 1694-1699.
Jin, Y., H. Wang, et al. (2009). "Reliable Remote-Monitoring Electrochemical
Potentiostat for Glucose Measurements." Tsinghua Science & Technology
14(5): 593-600.
Kounaves, S. P. and D. D. Lu (1992). "Acquisition, processing, and presentation of
3-D chromatovoltammographic data using an IBM PS/2 and par model 273
potentiostat." Computers & Chemistry 16(1): 29-33.
Sheu, Y.-H. and C.-Y. Huang (2007). "A Portable Potentiostat for Electrochemical
Sensors". 3rd Kuala Lumpur International Conference on Biomedical
Engineering 2006. F. Ibrahim, N. A. A. Osman, J. Usman and N. A. Kadri,
Springer Berlin Heidelberg. 15: 538-542.
Yarnitzky, C. N. (2000). "Part I. Design and construction of a potentiostat for a
chemical metal-walled reactor." Journal of Electroanalytical Chemistry
491(1-2): 160-165.
B.H. Vassos and G.W.Ewing (1993), Analog and Computer Electronic for Scientists
, 4th ed , Willey , New York ,1993.
R.S. Nicholson and I.Shain (1964), Anal. Chem. 36 , 706
R.N Adams (1969 ), Electrochemistry at Solid Electrodes ,Dekker , New York
Kissinger, P.T.; Heineman, W.R. J. Chem. Educ., 1983, 60, 702..
APPENDIX A
Table 5.1 : i-E for cyclic voltammetry measurements vitamin C in distilled water
Voltage(mV)
Anode Slope (µA)
Cathode Slope (µA)
0
100
0
5
100
0
10
100
0
15
100
0
20
100
0
25
100
0
30
100
0
35
100
0
40
100
0
45
100
0
50
115
0
55
125
0
60
135
0
65
146
0
70
160
0
75
180
0
80
190
0
85
212
0
90
235
0
95
220
15
100
180
35
105
165
42
110
150
43
115
130
45
120
120
112
APPENDIX B
Table 5.2 i-E for cyclic voltammetry measurements glucose in distilled water
Voltage(mV)
Anode Slope (µA)
Cathode Slope(µA)
0
0.001
0.0001
5
0.001
0.0001
10
0.001
0.0001
15
0.001
0.0001
20
0.001
0.0001
25
0.001
0.0001
30
0.001
0.0001
35
0.001
0.0001
40
0.0015
0.0001
45
0.0018
0.0001
50
0.0022
0.0001
55
0.0025
0.0001
60
0.0022
0.0001
65
0.0019
0.0001
70
0.0018
0.0001
75
0.0016
0.0001
80
0.0012
0.0001
85
0.001
0.0001
90
0.0008
0.0001
95
0.0006
0.0001
100
0.0005
0.0001
105
0.0003
0.0001