ECE_599_SDS_TwoElectrodePotentiostat_Rev_0.doc

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1

UNIVERSITY OF LOUISV
ILLE

Two Electrode Potentiostat

System Design Specification


Lucas Bennett

11/12
/2011

Revision
0



This is the System
Design

Specification for the
Two Electrode Potentioststat.



2

0.2

Table of Contents

1.0

System Description

................................
................................
................................
...........................

4

1.1 System Interfaces

................................
................................
................................
................................

4

1.1.1 USB Connection
................................
................................
................................
............................

4

1.1.2 Digital to Analog Convertor (DAC)

................................
................................
...............................

4

1.1.3 Digital Potentiometer (POT)
................................
................................
................................
.........

5

1.1.4 Digita
l Relay Control Module

................................
................................
................................
.......

5

1.1.5 PC with USB Connection

................................
................................
................................
..............

5

1.1.6 Power Connection

................................
................................
................................
........................

5

1.1.7 Electrodes
................................
................................
................................
................................
.....

5

1.2 Major Components

................................
................................
................................
.............................

5

1.2.1 Data Display Management System

................................
................................
..............................

5

1.2.2 Arduino Development Board

................................
................................
................................
.......

6

1.2.3 Daughtercard

................................
................................
................................
...............................

6

1.2.3.1 Digital to Analog Converter

................................
................................
................................
.......

6

1.2.3.1 Digital Potentiometer

................................
................................
................................
...............

6

1.2.3.1 Digital Relay Control Module

................................
................................
................................
....

6

2.0 Detailed Design

................................
................................
................................
................................
.......

6

2.1 Data Display Management System

................................
................................
................................
.....

6

2.1.1 DDMS GUI Frame

................................
................................
................................
.........................

7

2.1.1 Serial Communication

................................
................................
................................
..................

8

2.1.2 Data Logger

................................
................................
................................
................................
..

8

2.1.3 Data Visualization
................................
................................
................................
.........................

9

2.2 Arduino Development Board

................................
................................
................................
..............

9

2.3 Daughtercard

................................
................................
................................
................................
....

15

2.3.1 Digital to Analog Converter

................................
................................
................................
........

16

2.3.2 Digital Potentiometer (POT)
................................
................................
................................
.......

18

2.3.3 Digital Relay Control Module

................................
................................
................................
.....

20

3.0 Principles of Operation

................................
................................
................................
.........................

20

3.1 Data Display Management System

................................
................................
................................
...

20

2.3.2 GUI Operation

................................
................................
................................
............................

20



3

3.2 Arduino Development Board

................................
................................
................................
............

21

3.3 Daughtercard

................................
................................
................................
................................
....

21

4.0 Test Procedures

................................
................................
................................
................................
....

21

4.1 System Testing

................................
................................
................................
................................
..

21

5.0 Requirements Traceability

................................
................................
................................
....................

22

6.0 List of References

................................
................................
................................
................................
..

23




4

1.0

System Description



Figure
1
: System Block Diagram

The
Two Electrode Potentiostat
system will
a system used for the characterization of various
devices over voltage, current and load ranges.

The

system will implement a two electrode
configuration that will allow for such measurements to occur. These measurements will be
controlled by the daughtercard. The system is designed so that the user can control the
measurements intuitively using a Graphic
al User Interface
belonging to the Data Display
Management System.
In the system, a set of
leads are connected to an analog input going into the
daughtercard. These leads will attach to outside electrodes for obtaining measurements.

The
measurements will
then be collected and packaged up by the Arduino Development Board and
returned to the user’s Graphical User Interface.


1.1
System Interfaces

1.1.1

USB Connection

The system will be utilized by the user through the use of the DDMS running on a Personal
Co
mputer (PC).

To connect this major system component to the rest of the system a Universal
Serial Bus (USB) connection will be implemented between the components.

1.1.2

Digital to Analog Convertor (DAC)

For further system communication a DAC must be utiliz
ed. The Arduino Development Board
establishes communication with the DAC through the use of an SPI bus and a control digial


5

output pin. The DAC should be able to handle the requests of the Arduino Development Board
and output voltage between 0
-
5V according
ly.

1.1.3

Digit
al Po
tentiometer (POT)

For system implementation, the utilization of a POT is imperative. The Arduino Development
Board establishes communication with the POT using an SPI bus as well as a control digital
output pin.

The POT should be able t
o handle requests from the Arduino Development Board
and set resistance between 0

Ω and 50kΩ accordingly.

1.1.4

Digital Relay Control Module

For handling communication purposes, a Digital Relay Control Module will be implemented. For
communication a digital output pin will be utilized. This will allow for the connection between
the Ardu
ino Development Board and the DAC.

1.1.
5

PC with USB Connection

Since communication through the
major system components will rely heavily on a USB
connection, it is necessary that this external interface is in place. Since most modern computers
have this c
apability, it should not be of much concern.

1.1.6

Power Connection

The measurements taken by a Potentiostat are electrical by nature; as such, a power supply to
the system will need to be implemented. The power supply will only feed power to the Arduino
D
evelopment Board and Daughtercard componenets. The supply will come to these
components via the USB connection with the PC.

1.1.7

Electrodes

For the system to
accept measurements, the Daughtercard will contain a set of two leads, one
positive and one negat
ive, which will be connected with an analog input. This analog input will
connect using a 2.5mm headphone jack on the Daughtercard. The leads will have to attach to
electrodes on the device under testing(DUT).


1.2
Major Components


The system is composed
of
three

major components:
Th
e Data Display Management System
,
The Arduino Development Board
,
and the Daughtercard.

1.2.1
Data Display Management System

The DDMS will be operated on PC running on any operating system. The DDMS will be operated
through the
use of a GUI. It is through this GUI the user will have the means for managing the
entire Two Electrode Potentiostat system. The DDMS
must

provide a platform for displaying the
user interface, setting configuration parameters, data logging and communicatio
n between the
DDMS and the Arduino Development Board.



6


1.2.
2

Arduino Development Board

The Arduino Development Board will provide a means for interfacing the system components. It
must have a USB connection for communication with the DDMS. It should be pro
grammed with
the appropriate firmware for transmitting data to and from the DDMS. Once the firmware has
decoded the configuration parameters from the DDMS it will communicate the desired
measurements with the Daughtercard via an SPI bus.

1.2.
3

Daughtercard

The Daughtercard is a custom circuit board that is responsible for the capturing the current,
voltage and load measurements across DUT’s by utilizing a two electrode configuration. The
Daughtercard can be broken into three subcomponents.

1.2.3.1
Digital t
o Analog Converter


See 1.1.2

1.2.3.1
Digital Potentiometer


See 1.1.3

1.2.3.1
Digital Relay Control Module


See 1.1.4


2.0
Detailed Design

2.1
Data Display Management System


The Data Display Management System will function as a major component on a PC. I
t will
communicate to the rest of the Two Electrode Potentiostat system using a USB interface.

The type of PC will not be of concern as the DDMS will be written in the environment free
programming language Java. The minimal amount of memory to run the DDM
S should be
512 MB of RAM. The DDMS should operate on a 32 bit processor environment with the
best intentions of providing 64 bit support.

The PC should have the ability to run Java
Applications and will require the support of the RXTX library.

The figure
below illustrates how the software is organized.



7

Control Board Firmware
On
-
Board FTDI to USB Convertor
Serial Port Drivers
32
-
bit Operating System
RXTX Communication Package
Graphical User Interface
Run on Laptop
Run on Potentiostat Control Board
Custom Software
COTS Software
/
Hardware
USB

Figure 2: Software System Diagram

2.
1
.
1

DDMS
GUI
Frame


The GUI, will be a Netbeans designed frame which will provide the user with means of
controlling the Two Electrode Potenti
ostat system. The frame will contain functionality for
allowing the user to connect the DDMS to the other components via a USB connection. It
will also allow for the selection of the type

of Potentiostat measurement as well as the
parameters of the measure
ment. Additionally, it will allow for the input of a file path where


8

the logged data will be stored.

Finally, the frame will also display a table of live
measurements to the user.

2.
1
.
1

Serial Communication


The Arduino Development Board will check for dat
a packets sent from the DDMS are
available. The DDMS will send the packets in the form described in the figure. The DDMS will
receive packets from the Arduino Development Board in the figure below. It will take this
data and convert it to usable data that
can be read by the user or logged.

MSB ………………………………………………………… LSB
5
Bytes of Serial Data
Char
[
4
]
Data Bytes
(
char
)
MSB …………………………………………………
.
……
.
LSB
Char
[
3
]
Char
[
2
]
Char
[
1
]
Char
[
0
]

Figure 3: GUI Data Packet (Received)


Control
Bits
MSB ………………………………………………………… LSB
11
Bytes of Serial Data Comma Separated
with Start and Stop Byte
Data Bytes
(
int and char
)
MSB ……… LSB
Int
[
10
]
Start
Stop
Int
[
9
]
Int
[
8
]
Int
[
7
]
Int
[
6
]
Int
[
5
]
Char
[
4
]
Char
[
3
]
Char
[
2
]
Char
[
1
]
Char
[
0
]
“Go”
“ST”

Figure 4: Control Board GUI Update Packet (Transmitted)


2.
1
.
2

Data Logger


The data logger is responsible for storing all r
eturned measurements of the other two
components of the Two Electrode Potentiostat system. Each time a measurement is received,
the DDMS is responsible for storing the values into a prestructured CSV file.



9

2.
1
.
3

Data Visualization


The data visualization i
s designed so that the user can watch a live feed of the measurements
being taken by Two Electrode Potentiostat system. The values will be displayed in uneditable
form fields.

The readings will include voltages, currents, and times.


2.
2

Arduino Developmen
t Board


The control board that was selected for the system
the Arduino Development B
oard
. The board
is open sources and based on the Atmel ATMega328 microcontroller.

The board will utilize many
of its components such as the Digital Pins, Analog Input Pins
,
FTDI USB chip
and the USB Jack.


Figure 5: Arduino Development Board

The
Arduino Development Board will serve the Two Electrode Potentiostat as a central interface
between the major components.

Due to the open source platform and diverse nature of the
A
rduino Develop
ment Board, it can easily be used in many other systems as well as allowing for
future expansion without platform changes.

The Arduino firmware is responsible for initializing the USB connection with the DDMS as well as
the POT and DAC.

The
POT and DAC will be set to safe and known values to prevent hardware
failure.




10

When the Arduino is connected to the DDMS via the USB cable,

it will check for data packets
from the DDMS. If they exist, i
t will read the binary packets as described in Section

2.1.1. The
firmware on the Microcontroller should decompile the data and instruct the Daughtercard
measurement process with the SPI bus.
This process will be executed in a set number of loops.
When results are obtained on the Daughtercard and returned to
the Arduino, they will be sent
back to the DDMS using the schema described in Section 2.1.1.

The execution of the firmware on the Arduino

when operating in Potentiostat mode

follows a
simple flow chart testing mechanism which can be seen below.



11

Start Up
Read Serial
Modify Parameters
Run the
Potentiostat
Function
Run the Galvanostat
Function
Run the test
_
dac
function
Send Data to serial
Potentiostat
Active
?
Serial data
available
?
Is the DAC in
test mode
?
Galvanostat
Active
?
Yes
Yes
Yes
Yes
No
No
No
No
Run the test
_
pot
function
Is the POT in
test mode
?
Yes
No
Sufficient cycles
complete
?
Yes
No

Figure 6: Control Board Software State Diagram

These operations are based on the main Potentiostat Function equation which can be seen in
the following figure.





12


Figure 7: Potentiostat Function Equations

The system will also have the a
bility to function in a Galvanostat mode. This mode’s execution
will be based on the following flow chart.

Start Up
Measure Vcell and
Vdac
Decrease DAC
Increase DAC
Is
((
Vdac


Vcell
)
<
setpoint
)
?
Is
((
Vdac


Vcell
)
>
setpoint
)
?
No
Is
(
outvoltl
>
0
)
?
Is
(
outvoltl
<
1023
)
?
No
Yes
Yes
Yes
Yes
Increase DAC
Decrease DAC
Is
((
Vcell


Vdac
)
>
setpoint
)
?
Is
((
Vcell


Vdac
)
>
setpoint
)
?
No
Is
(
outvoltl
<
1023
)
?
Is
(
outvoltl
>
0
)
?
No
Yes
Yes
Is
(
sign
>
0
)
?
Yes
Yes
Is
(
sign
<
0
)
?

Figure 8: Potentiostat Function Flow Diagram


These operations are based on the equations seen in the following figure.








13


Figure 9: Galvanostat Function Equations


The execution process of the Arduino firmware will follow the state diagram in the following
figure when determining how to configure the Daughtercard for measurements.

Open Relay
Update POT
Close Relay
Update
Potentiostat
Prep
Potentiostat
Prep
Galvanostat
Test DAC
Test POT
Decide
+
-
P
R
r
g
p
c

‘+’



Update DAC



Close RELAY



Loopspeed = 5



Countto = 10


-




Ocv = TRUE



Open RELAY



Loopspeed = 5



Countto = 10

‘P’



DACTest = TRUE



Testcount = 0



Testlimit = 1023

‘R’



Rtest = TRUE



Testcount = 0



Testlimit = 255

‘r’



Update POT

‘g’



Gstat = TRUE



Update DAC to Vcel
l



Determine if current is charging or


14

discharging



Update DAC with corrected
setpoint



Close RELAY

‘p’



Pstat = TRUE



Update setpoint



Close RELAY

‘c’



Pstat = TRUE



Update setpoint



Close RELAY

Figure 10: Deicde State Diagram/Chart





15

2.
3

Daughtercard

The
Daug
htercard is responsible

for the electrical processes necessary to obtain Potentiostat
measurements. It is constructed using a simple circuit which can be seen in the figure.



Figure 11: Daughtercard Layout


Once assembled, the board is very modest and c
an be seen in the figure.



16

.


Figure 12: Picture of Assembled Daughtercard


It comprised of three subcomponents:

2.
3
.
1

Digital to Analog Converter


The DAC will be mainly responsible for managing specific gain configurations, remote sensing,
serial data o
utput and high output drive capacity. In addition, the DAC will have the ability for an
active
-
low reset. This reset will clear all registers and DAC’s to zero.

For the DAC, a +5 MAX5250 will be implemented. This chip combines four low
-
power, voltage
outpu
t, 10
-
bit DAC’s and four precision output amplifiers. The precision output amplifiers are
configured in a 20 pin package to save space.



17

AGND
1
FB
-
A
2
3
Out
-
A
4
Out
-
B
VDD
FB
-
D
Out
-
D
Out
-
C
20
19
18
17
FB
-
B
5
REFAB
6
7
RST
/
CLR
8
CS
FB
-
C
REFCD
PowerDown
Logic Out
16
15
14
13
Ser
.
IN
9
CLK
10
Ser
.
OUT
DGND
12
11


Digital to Analog
Convertor
MAX
5250
R
1
10
k

R
2
10
k

R
4
100

+
5
V
Black
R
3
100


Figure 13:
Max 5250 Pinout

The DAC’s each have double
-
buffered input organized as an input
register followed by a DAC
register.

The DAC is controlled by the Arduino thru the usage of the SPI Bus. The data packets received by
the DAC following the schema of the figure.
This 16
-
bit serial word loads data into each of the
inputs and DAC registers.
In addition to the data carried in the packet, the address is also
received which will allow for future expansion of the other DAC’
s on the D
aughtercard.

MSB……………………………………………………………
.
LSB
16
Bits of Serial Data
Address
Bits
A
1
A
0
C
1
C
0
Control
Bits
D
9
………………
..
D
0
S
1
S
0
Data Bits
(
10
+
2
)
MSB………………………
..
LSB

Figure 14: write_dac Function Packet


The three wire serial interface is
compatible with SPI™/QSPI™ and Microwire™. With this
compatibility, the registers are able to act both independently and
simultaneously

with a single
command from the Arduino.



18

Of the four DAC’s only one is to be implemented, but future expansion can utiliz
e the remainder
DAC’s in addition to the input buffers for a three electrode Potentiostat configuration.

A feedback resistor and a voltage reference resistor are required for operation of the MAX5250.
For this system, two 10k
Ω

resistors will be used for the feedback resistor(as noted by R1 and R2
in the following figure) and two 100k

Ω

resistors for the voltage references(as noted by R3 and
R4 in the following figure). The voltage reference resistors will form a voltage divide
r operation
which will place a 2.5V voltage on the Vref pin.


Figure 15: Digital to Analog Converter Block Diagram



2.
3
.
2

Digital Potentiometer (POT)


For the POT, an MCP4261 chip will be implemented. This chip is an 8
-
bit Dual SPI Digital
Potentiometer
with Non
-
Volatile Memory. There are several models available for this chip, but
for this system the 503e will be utilized. With this model, the POT will be adjustable in the range
between 0
Ω



50k
Ω.

There will be a series of equal value resistors (RS) that establish the resistor ladder (ladder).
There will be a connection point (TAP) between the two resistors. By increasing or decreasing
the number of resistors in the ladder, a desirable amo
unt of resistance can be achieved.

The end
points of the resistors are connected to analog switches which are connected to the Terminal A
and Terminal B pins. Since this is an 8
-
bit device only 256 resistors in a string are available. This,
in addition to
the Terminal A and Terminal B settings, provide for a maximum possibility of 257
settings which can be set to be accessed by the wiper.



19


Figure 16: Digital Potentiometer Block Diagram


The POT is controlled by the Arduino thru the usage of the SPI Bus. Th
e data packets received by
the POT following the schema of the figure.

The data can be used to adjust the resistance
between a single terminal (which in this system will be Terminal B and the wiper).

In addition to
the data carried in the packet, the addre
ss is also received which will allow for future expansion
of the other POT’s on the Daughtercard

MSB ………………………………………………………… LSB
16
Bits of Serial Data
Address Bits
(
4
)
MSB ……
...

.
LSB
A
3
A
2
A
1
A
0
D
9
………………
..
D
0
Data Bits
(
10
)
MSB ………………………
.
LSB
MSB ………………………………………………………… LSB
16
Bits of Serial Data
Address
Bits
A
3
A
2
A
1
A
0
D
9
………………
..
D
0
Data Bits
(
10
)
MSB ……………………
.
LSB
Control
Bits
C
1
C
0


Figure 17: write_pot Function Packet




20

2.
3
.
3

Digital Relay Control Module


The Digital Relay Control Module is an R56
-
1D.5
-
6 imple
mented in an SPST
-
NO relay so that the
DAC and POT can be removed for an unimpeded measurement. The relay will receive
communication from the Arduino via the Digital Output pin. The figure below shows illustrates
the Digital Relay Control Module.



Figure

18: Relay Control Module


3.0
Principles of Operation

3.1
Data Display Management System

2.
3
.
2

GUI Operation


The GUI’s main purpose is to provide the user with an easy means of controlling the DDMS and
subsequently, the rest of the Two Electrode Potentio
stat system. To begin execution of the GUI,
the user runs the .JAR file. This will display the GUI frame which is designed to be very intuitive.

The user will begin

the Two Electrode Potentiostat system measurement process by first
connecting the rest of t
he major components to the computer running the DDMS via a usb
cable. Once the cable is connected, the user can click the Get Ports button which will scan the
USB ports for devices. These devices will be displayed in a drop down field above the Get Ports
b
utton. Once the user selects the Potentiostat device, he can then click connect to establish the
connection with the rest of the system.



21

Underneath the connection section, there is a section which will allow the users for specifying
the parameters the syst
em will use to execute Potentiostat measurement testing. First the user
will select the type of measurement from a list of radio buttons.

The user will then have a drop
down with different types of modes that can be selected.

The modes are as follows:

Mode

0: Will hold a constant current (mA) until a specified cutoff potential (V) is reached.

Mode 1: Will hold a constant current (mA) for a specified amount of time(s).

Mode 2: Will hold a constant potential (V) until a cutoff current (mA) is reached.

Mode 3:

Will hold a constant potential (V) for a specified amount of time(s).


Once the measurements are received by the DDMS, they will be displayed in an always visible
and constantly updated section of fields.

Finally, the user will have the ability to log thi
s data in a CSV file. To specify the file name, there
is a text input field for the user. Underneath, is a button
that when pressed, will store all of the
mentioned above displayed results into the CSV file.

3.
2

Arduino Development Board


The purpose of th
is component is to act as the central interfacing of the components of the
system. In addition, it is responsible for the microcontroller process executed of the system. The
Arduino will receive packets from the DDMS and based of them, the firmware will cr
eate a set of
instructions for the Daughtercard to make measurements of a DUT. Once received, these
measurements will be repacked into data that the DDMS can utilize.


3.
3 Daughtercard

The main purpose of the Daughtercard is to take the measurements of a g
iven DUT and return
the results to the Arduino utilizing a two electrode Potentiostat configuration. The process will
be automated by the firmware instructions received from Arduino. The process will utilize the
DAC’s, POT’s and Digital Relay Control.

4.0
Test
Procedures

4.1
System Testing


To begin the testing process, a user will need to configure the system appropriately by attaching
all components. The DDMS will be connected to the rest of the system thru the use of a USB


22

cable. The Daughtercard will at
tach to two electodes of a DUT. This test will measure the
chemical redox reactions of acid orange juice. The orange juice will be placed in a beaker
containing two pencil lead electrodes attached to the rest of the system via alligator clips.


Once the DD
MS establishes a connection with the system, the GUI of the DDMS will then be
configured to run

the Cyclic Voltammetry test on the DUT. The test for comparison will be run in
parallel with the Three Electrode Potentiostat groups testing. This will mean tha
t a Mode 3 test
will be executed to measure a constant potential of 3 Volts for 5 seconds.

These results will be logged utilizing the features of the DDMS into a CSV file. These results can
be then manipulated into a meaningful graph.

The results of the t
est will be evaluated based on an eye inspection test against two other
graphs. The first graph will be the result of the Three Electrode Potentiostat group.

The second
graph of comparison is the results of tests in the “Cheap Stat: An Open Source,…” artic
le.

These evaluations will provide for a better understanding of the differences of a two and three
electrode Potentiostat configuration.

5.0
Requirements Traceability


Requiremen
t
Number

Requirements

Test

Pass/Fail

R1

Develop an Inexpensive Potentiostat
for use in
a lab setting

T1

Passed

R2

Document firmware for ease of use and later
modification

T2

Passed

R3

Document Potentiostat so that it can be
produced by unskilled users

T3

Passed

R4

Log data for later analysis

T4

Passed

R5

Provide an Intuitive G
UI for user

T5

Passed

R6

Make recommendations for expanding Two
Electrode Potentiostat to a three electrode
configuration

T6

Passed









Test Number

Tests

Requirement
Fulfilled



T1


Can the system return chemical redox reaction
measurements to the

user

R1



T2

Firmware be easily understood and edited

R2





23

T3

All circuit diagrams are available in addition to
material lists

R3



T4

Measurement results are recorded to a CSV
file.

R4



T5

Can program be ran without documentation.

R5



T6

Can 2 Ele
ctrode Potentiostat graphed results be
compared with 3 Electrode Potentiostat

R6



6.0 List of References


[1] Ardustat, Department of Chemical Engineering, CCNY. [Online]

http://steingart.ccny.cuny.e
du/ardustat

[2] Arduino. Arduino IDE Download. [Online]

http://arduino.cc/en/Main/Software

[3] Arduino. Arduino Programming Reference. [Online]

http:
//arduino.cc/en/Reference/HomePage

[4] Atmel. AtMEGA328 Datasheet. [Online]

http://atmel.com/dyn/resources/prod_documents/8271S.pdf

[5] MAXIM. MAX5250 Digital to Analog Converter Data
sheet. [Online]

http://www.maxim
-
ic.com/datasheet/index.mvp/id/1650

[6] Microchip. MCP4261 Digital Potentiometer Datasheet [Online]

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en531252

[7] NTE Inc. NTER56 Relay Datasheet. [Online]

www.nteinc.com/relay_web/pdf/R56_57.pdf

[8] Oracle.

Java Virtual Machine Download. [Online]

http://www.java.com/en/download/index.jsp

[9] NetBeans. Java Programming IDE Download. [Online]

http://www.netbeans.c
om/

[10] CadSoft. Eagle PCB Design Software. [Online]



24

http://www.cadsoftusa.com/

[11] Gamry. Commercial Potentiostat. [Online]

http://www.gamry.com/

[12] Princeton Applied Research. Commercial Potentiostat. [Online]

http://www.princetonappliedresearch.com/

[13] Uniscan Instruments. Commercial Potentiostat. [Online]

http://www.uniscan.com/

[14] Rowe AA, Bonham AJ, White RJ, Zimmer MP, Yadgar RJ, et al. (2011) CheapStat: An Open
-
Source,
“Do
-
It
-
Yourself” Potentiostat for Analytical and Educational Applications. PLoS ONE 6(9): e23783.
doi:10.1371/journal.pone.00
23783

[15]
Rowe, Aaron A., et. al. "PLoS ONE: CheapStat: An Open
-
Source, “Do
-
It
-
Yourself” Potentiostat for
Analytical and Educational Applications."

PLoS ONE : Accelerating the Publication of Peer
-
reviewed
Science
. Web. 14 Nov. 2011.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023783

[16] Williams, Benjamin. 2011. Potentiostat Development, Final Report.