eDAQ User Manual

BANK Elektronik
Potentiostat Adaptor

BANK Potentiostat Adaptor
EA169

On-linee-corder®

Scan

www.eDAQ.com

This document was, as far as possible, accurate at
the time of printing. Changes may have been madeto the software and hardware it describes sincethen: eDAQ Pty Ltd reserves the right to alterspecifications as required. Late-breaking information
may be supplied separately. Latest information andinformation and software updates can be obtained
from our web site.
Trademarks of eDAQ
e-corder and PowerChrom are registered trademarksof eDAQ Pty Ltd. Specific model names, such as
e-corder 201, PowerChrom 280, Picostat and
QuadStat are trademarks of eDAQ Pty Ltd. Chartand Scope are trademarks of ADInstruments Pty Ltd
and are used under license by eDAQ. EChem is atrademark of eDAQ Pty Ltd.

Products: eDAQ BANK Elektronik Potentiostat
Adaptor (EA169)
Document Number: UM-EA169-0707
Copyright © July 2005
eDAQ Pty Ltd
6 Doig Avenue
Denistone East, NSW 2112
Australia
http://www.eDAQ.com
email: info@eDAQ.com
All rights reserved. No part of this document may be
reproduced by any means without the prior written
permission of eDAQ Pty Ltd.

Other Trademarks
Mac OS, and Macintosh, are registered trademarksof Apple Computer, Inc. Windows 98, Windows
Me, Windows 2000, and Windows XP aretrademarks of Microsoft Corporation.
PostScript, and Acrobat are registered trademarks ofAdobe Systems, Incorporated.
All other trademarks are the properties of theirrespective owners.

ii

eDAQ BANK Elektronik Potentiostat Adaptor

Contents
1 Overview 1
How to Use this Manual 2eDAQ Amps 2
Checking the unit 3

Chronocoulometry

31

A Troubleshooting 33
B Specifications 39

2 The Bank Elektronik Adaptor 5
The Front Panel 6
The Online Indicator 6
The Scan Indicator 6
The Back Panel 7
E Out, I Out and E In Connectors 7
I2C Connectors 7
Potentiostat Interface Port 8
Connecting the Adaptor 8First Use 10
Adaptor Control Window 11

Index 41
License & Warranty 43

3 Techniques 17
Introduction 18
Linear Scan Techniques 18
Fast Cyclic Voltammetry 19
Chronoamperometry with Chart 21
On Windows computers 21
On Macintosh 22
Analysis of Chronoamperometry 25
Chronoamperometry with Scope 28

eDAQ BANK Elektronik Potentiostat Adaptor

iii

iv

eDAQ BANK Elektronik Potentiostat Adaptor

C H A P T E R

1 Overview

O N E

The eDAQ BANK ETektronik Potentiostat Adaptor is designed to workwith any e-corder data acquisition system and a BANK Potentiostat,model:• LPG03• LPG03_2A• POS2• POS2_2A• PGS95• HP96_10A• HP400_10A• HP96_20
Direct software control over many of the potentiostat front panel
functions is provided. The eDAQ Chart, Scope, and EChem software all
can make use of the Adaptor to provide a variety of electrochemical
techniques. Please read the eDAQ Potentiostats Manual and the EChem
Software Manual for an outline of the experimental settings for thesetechniques.
Please read you BANK Potentiostat manual to familiarise yourself with
its front panel controls. Some BANK Potentiostats generate large
voltage/current combinations which can be dangerous to the user!

eDAQ BANK Elektronik Potentiostat Adaptor

1How to Use this ManualThis manual describes how to set up and begin using your Adaptor(Chapter 3).
The appendices provide technical and troubleshooting information.
See the EChem Software Manual for a description of the use of thesepotentiostats with the optional EChem software.

eDAQ Amps
The Adaptor is one of a family of preamplifiers known as eDAQ Amps
which are designed to be operated under full software control and areautomatically recognised by Chart, Scope or EChem software which
control their gain range, signal filtering, and other settings.
The eDAQ Amp family includes the:• Potentiostat (model EA161). Single channel, three electrodepotentiostat/galvanostat with gain ranges of 20 nA to 100 mA;• Picostat (model EA162). Single channel, three electrode, highsensitivity potentiostat with gain ranges of 10 pA to 100 nA; and• QuadStat (model EA164). Four channel, three electrodepotentiostat with gain ranges of 2 nA to 10 mA with current signal
offset.
• Quad pH Amp (model EA168), suitable for connection of up to
four pH, ion selective, and potentiometric (ORP) electrodes. Eachchannel is electrically isolated.
• Quad Tc Amp (model EA150), suitable for connection of up to
four thermocouples. Each channel is electrically isolated.
• C4D Amp (model EA120). Capacitively coupled contactless
conductivity detector for capillary, and microfluidic channel,
electrophoresis.
• GP Amp (EA142), suitable for high output sensors requiring ahigh impedance DC Wheatstone bridge. Also provides DC
excitation.

2eDAQ BANK Elektronik Potentiostat Adaptor

See our web site at www.eDAQ.com for more information.

Checking the unit
Before you begin working with the Adaptor please check that:• all items described in the packing list are included; and that• there are no signs of damage that may have occurred duringtransit.
Contact your eDAQ distributor if you encounter a problem.
You should also become familiar with the basic features of youre-corder system, which are discussed in the e-corder Manual which will
be installed as a pdf file on your computer when you install thesoftware.

Chapter 1 — Overview

34eDAQ BANK Elektronik Potentiostat Adaptor

C H A P T E R

T W O

2 The Bank Elektronik
AdaptorThis chapter describes how to connect and use your Bank Elektronik
Potentiostat Adaptor.
▲ WARNING!
Some models of
BANK potentiostat arecapable of producing
large currents andhigh voltages. Please
read the BANK
potentiostat manual tofamiliarise yourself
with any possible
hazard and correct
operating procedure.

IMPORTANT: Always make sure that the e-corder is turned off before
you connect or disconnect the Potentiostat Adaptor unit. Failure to do
this may result in damage to the e-corder and/or the Adaptor unit.

eDAQ BANK Elektronik Potentiostat Adaptor

5The Front Panel
The front panel of the Adaptor is shown in Figure 2–1

The Online Indicator
When lit, the green Online Indicator, Figure 2–1, shows that thesoftware (such as EChem, Chart or Scope) has located and initialised
the Intefrace. If the light does not go on when the software is run, checkthat the Adaptor is properly connected. If there is still a problem, pleaserefer to Appendix A, page 33.

The Scan Indicator
When lit, the yellow Scan indicator, Figure 2–1 shows when the sweep
generator in the Bank Elektronik potentiostat is active. Note that not allmodels of Bank potentiostat contain a sweep generator.

BANK Potentiostat Adaptor
EA169

Figure 2–1
The Bank Elektronik
Potentiostat Adaptor,
front panel.

On-lineE Out

Figure 2–2
The Bank Elektronik
Potentiostat Adaptor,
back panel.

E In

OutputI 2C Bus

Input

6

I Out

Scan

Potentiostat Interface

eDAQ BANK Elektronik Potentiostat Adaptor

The Back Panel
The back panel of the Adaptor is shown in Figure 2–2.

E Out, I Out and E In Connectors
The Adaptor back panel has three BNC connectors labelled E Out,I Out, and E In.
The Adaptor provides two signals from the potentiostat: the current
signal (I Out) indicating the current flow between the working andauxiliary/counter electrodes, and the potential signal (E Out) indicating
the potential difference between the working and reference electrodes.
For most situations I Out is connected to e-corder Input 1, and E Out toe-corder Input 2, Table 2–1. The description of operation in this manualassumes you have followed this convention. However, when you areusing Chart software and recording data from various sources on morethat just two channels, you may want to connect the Adaptor to othere-corder input channels.
The Adaptor E In is connected to the Output of the e-corder, usually
Output + is used. To reverse the polarity of the Adaptor andpotentiostat use e-corder Output –.

I2C Connectors
The Adaptor back panel, Figure 2–2, has two DB-9 pin ‘I2C bus’
connectors labelled Input and Output. The Input connector provides
power to the Adaptor and carries the various control signals (for mode,
gain range, and filter selection) to and from the e-corder. A cable isTable 2–1
Adaptor to e-corderconnections, analog
signals.

Adaptor back panel

e-corder front panel

I Out

Input 1E Out

Input 2E In

*Output +* Use Output – to reverse the polarity of the applied potential

Chapter 2 — The Bank Elektronik Adaptor

7

6

INT

DSD

SDA

DSC

I2C control signals

SCL

Regulated +17 V DC

Regulated +8 V DC

Digital Ground

Regulated –17 V DC

Power lines
Regulated –17 V DC
Digital Ground

INT
DSD
SDA
DSC
SCL

1

Regulated +17 V DC
Regulated +8 V DC

I2C control signals

Figure 2–3
The pin assignments for
the I2C DB-9 connectors.

5

5

1

9

9

6

Input

Outputprovided for this purpose. The pin assignments are shown in Figure
2–3.
The Output connector can be used for the attachment of a second
Adaptor of for attachement of eDAQ Amps.
More information about the I2C connector can be found in youre-corder Manual.

Potentiostat Interface PortThe back panel, Figure 2–2, has a female DB25 pin Potentiostat
Interface port. This provides digital (TTL) control signals to be sent to,
and received from, the potentiostat.

Connecting the Adaptor
First make sure that the e-corder and potentiostat are switched off. Use
the cable supplied to connect the Potentiostat Interface Port to the backpanel of the Bank Elektronik potentiostat. Then connect the back panelsof the Adaptor and e-corder with the I2C cable. Next use the three BNC
cables to connect the back panel of the Adaptor to the front panel ofthe e-corder as shown in Table 2–1.

8eDAQ BANK Elektronik Potentiostat Adaptor

BANK Potentiostat Adaptor
EA169

Figure 2–4
The Adaptor shown
connected to an
e-corder, front view, as
descibed in Table 2–2.

OnlineScan

Input 1401

Input 2

Input 3

Power
Status

OutputInput 4

Trigger

Figure 2–5
The Adaptor shown
connected to an
e-corder, rear view, as
descibed in Table 2–2.

to BANK
potentiostat

With these connections, when you use the software to set a morepositive voltage, a more oxidising potential will be applied at theworking electrode. Such an arrangement is shown in Figure 2–4 andFigure 2–6.
To operate the potentiostat with reverse polarity connect Adaptor E In toe-corder Output –. With these connections, when you use the software
to set a more positive voltage, a more reducing potential will beapplied at the working electrode.
Check that all connectors are firmly attached. Loose connectors cancause erratic behaviour, or may cause the potentiostat to fail to work.
The Adaptor uses two e-corder input channels during normal operation
for the current (I Out) and potential (E Out) signals. The remainder ofthis chapter assumes that you have connected the current signal toe-corder Input Channel 1 and the potential signal to e-corder Input
Channel 2. (It is possible when using Chart or Scope software to

Chapter 2 — The Bank Elektronik Adaptor

9connect the Potentiostat to other e-corder input channels, in which casethe description that follows would change accordingly).
When using EChem software, Channel 1 is always set to be the current
signal (the I channel), and Channel 2 is automatically set to be thepotential signal (the E channel). Thus when using EChem software you
must always connect the current signal (I Out) to e-corder Input Channel
1, and the potential signal (E Out) to e-corderInput Channel 2.
Channel 2 normally displays the applied potential, and its settings arecontrolled using the standard Input Amplifier dialog box, described in
the Chart Software Manual and Scope Software Manual on the eDAQ
Installer CD.

First Use
After you have installed the software, connected the e-corder andcomputer as described with the booklet supplied with the e-cordersystem, and connected the Adaptor and potentiostat as describedabove, you are ready to begin.
Switch the range knob on the potentiostat to REM (remote). Turn thepotentiostat on and allow it several minutes to warm up.
When the e-corder is turned on, and Chart (or Scope or EChem)
software started, the Adaptor Online indicator (green) should light,
Figure 2–1, page 6.
From the Channel 1 Function pop-up menu, select the ‘Bank Elektronik’
command, which opens the Control window, Figure 2–6 (Windows).
This window allows you to preview the current signal without actually
recording the signal to your computer’s hard disk. (If the menu says
‘Input Amplifier’ instead of ‘Bank Elektronik’ or ‘BANK’ then thesoftware has not recognised the Adaptor. Exit the software, check all
your connections and try again).
By default, the control window opens with the potentiostat in Standby
mode, that is with the counter electrode isolated so that no current willflow through your electrodes. To connect to the Potentiostat lead wires
you must select Real mode. When you click Cancel or OK the
Potentiostat will revert to Standby mode until recording is started.

10

eDAQ BANK Elektronik Potentiostat Adaptor

Adaptor Control Window
With Chart software, the Adaptor Control window is accessed from the
Bank Elektronik command in the Channel Function pop-up menu. Figure
2–6 shows the control window on a Windows computer. This window
controls the various current ranges, filters, and operating modes of the
Potentiostat.

Model
The correct potentiostat model, page 1, must be selected from theModel menu. Some models may not offer all the controls described
below.

Modes of Operation
While the Mode box is unticked,, the potentiostat is in a restingstate equivalent to the ‘O’ position of the front panel Operation knob.
While in this state gain ranges cannot be selected.
, the Adaptor becomes fully active andWhen the box is ticked,
the potentiostat can now be operated in several different modes byselecting the appropriate radio button:• Potentiostat (Chart, Scope, and EChem software). This isequivalent to setting “Operation P” on the potentiostat front panel.
The current signal is provided at I Out, and the potential signal isprovided at E Out on the Adaptor back panel, Figure 2–2.
• Galvanostat (Chart and Scope software only). This is equivalent tosetting “Operation G” on the potentiostat front panel. The current
signal is provided at I Out, and the potential signal is provided at
E Out on the Adaptor back panel, Figure 2–2.
• –Er, high impedance voltmeter, (Chart and Scope software only).
This is equivalent to setting “Operation –Er” on the potentiostat front
panel. The high impedance potential signal is supplied at E Out, on
the Adaptor back panel, Figure 2–2;
Please make sure the electrode lead wires are connected appropriately
before operating in any of these modes. In particular, incorrect
placement of leads may damage the reference electrode.
Chapter 2 — The Bank Elektronik Adaptor

11Figure 2–6
Potentiostat Adaptor
controls with Chart
software. Potentiostat
mode.

Select Bank Elektronik in
the Channel pop-up menu
Pause/resume scrolling

Select potentiostat model
Select input
range
Select low-passfilterMains filter
on/offSignal invert

Signal display area

Remotecontrol on/off
Select mode

Counter
electrode
on/offApplied potential controls

Figure 2–7
Potentiostat Adaptor
controls with Chart
software. Galvanostat
mode.

Display of current signal. The
potential signal should beviewed on channel 2

Selectappliedcurrent
range

Selectgalvanostat
mode

Applied current control (when in galvanostat mode)

12eDAQ BANK Elektronik Potentiostat Adaptor

Note that not all modes may be available on all models of BANK
Potentiostat. Also Galvanostat and –Er modes are not available whenusing EChem software (which is designed for voltammetric experiments
requiring potentiostat mode only)

Signal Display
The current signal is previewed in the scrolling display area. Note thatthe signal is not being recorded to hard disk at this stage, and thatwhen the window is closed the signal trace will be lost.
By using Real cell, the counter electrode is activated and you caninvestigate the effect of the Applied Potential, page 15, on the current
signal.
You can stop/start the signal scrolling by clicking the Pause/Resume
button.
You can shift or stretch the vertical Amplitude axis to make the best useof the available display area.

The potential signal should
be viewed on channel 2

Not used in–Er mode (usecontrols onchannel 2–Er mode selected

Cell selector, not usedin –Er mode

Applied potential control, not used –Er mode

Chapter 2 — The Bank Elektronik Adaptor

13Setting the Range
Use the Range pop-up menu to select the input current range (channel
sensitivity). The resolution within each range is 16 bits or 0.0015%.
You should set the range so that it is larger than the biggest current thatyou expect to encounter during your experiment. If, during theexperiment the current signal exceeds the range, then the signal will go
off scale and be lost.

Filtering
The e-corder provides filter settings from 1 Hz to 2000 Hz (Chart
software). When filtering is Off the bandwidth of the e-corder is about
20 kHz. Always examine the signal without filtering before applying a
low pass filter. Excessive noise can indicate a problem with shielding of
the experiment, inadequate eartning of the power socket, or a problem
in locating the experiment to close to nearby ‘noisy’ equipment.

Figure 2–8
Accessing the
Potentiostat controls with
Scope software.

14

As a general rule a 10 Hz filter setting is highly effective for theremoval of mains hum (50 or 60 Hz interference) and should be
employed whenever possible. A 10 Hz filter should not be used forpulsed experiments where the pulses are shorter than 100 ms, or forvoltammetric experiments where rapid scan rates (greater than about
100 mV/s) are used, because it will distort the signal.
With Chart software, there is an additional Mains Filter checkbox,. If this is ticked, then the e-corder will apply a mains filtering
algorithm to the incoming signal which removes repetitive signals
occurring at 50 or 60 Hz which are typical of mains interference.
Lower and higher frequency compunents in the signal will be
unaffected. Note that the mains filter is not a notch filter, and that it canremove a 50 or 60 Hz interference even if it is not a pure sinusoidal
function. However, the mains filter does take a couple of seconds to‘learn’ the pattern of the interference so that you will need to record for
longer than this for it to have full effect. The mains filter can be
employed even for experiments in which there are sudden potential
jumps.

eDAQ BANK Elektronik Potentiostat Adaptor

Inverting the Signal
The Invert checkbox, allows you to reassign the direction (up or down)of an anodic (or cathodic) current. Please note that this affects thedisplay of the signal only — it does not reverse the direction of actual
current flow at the electrodes!

Cell Control
When in Potentiostat or Galvanostat mode you can select:• Standby: the counter electrode is unconnected (the ‘CE ON’ lighton the front panel of the potentiostat will be unlit). However, thecounter electrode will be connected when Potentiostat Control
window is closed and the Start button is clicked to begin theexperiment. Note that the Applied Potential (or Applied Current)
controls are disabled in this mode.
• Real: the counter electrode is connected (the ‘CE ON’ light on thefront panel of the potentiostat will light). Note that the Applied
Potential (or Applied Current) controls are enabled in this mode,
Figure 2–6, page 12 and Figure 2–7, and can be used to set thepotential (or current) applied to the electrodes while the Potentiostat
control window is open. When you close the control dialog (using
EChem or Scope software) the potentiostat will revert to Standby
mode until the Start button is clicked to begin a scan. If you areusing Chart software, the potentiostat will remain in Real mode (CEON) when the dialog is closed — so that when you start and stop
recording data the electrodes will remain active. This allows
periodic recording of the signal from, for example, amperometricbiosensors without disturbing the environment around the electrodes.

Applied Potential
The Applied Potential controls are enabled when Real cell is selected in
Potentiostat mode. It allows you to adjust the voltage applied to theelectrodes. The Range control limits the range over which the applied
potential can be set. Smaller ranges offer finer control with the sliderbar.

Chapter 2 — The Bank Elektronik Adaptor

15

Check thebox to remember the value of theapplied potential when the control window, Figure 2–6, page 12, isclosed. (The value is transferred to the Stimulator baseline control,
Figure 3–5, page 23).

Applied Current
The Applied Current controls are active when when Real cell is selected
in Galvanostat mode (replacing the Applied Potential controls). The
maximum applied current is determined by the setting of the Range
control.
Check thebox to remember the value of theapplied current when the control window, is closed. (The value istransferred to the Stimulator baseline control).

16

eDAQ BANK Elektronik Potentiostat Adaptor

C H A P T E R

3 Techniques

T H R E E

The Chart and Scope software supplied with your e-corder can be used
to perform many different electrochemical techniques. This chapter
provides an overview of these techniques, but you will need to also
refer to the Chart Software Manual and Scope Software Manual (which
are installed on the computer hard disk, with the software, or can befound on the eDAQ Installer CD).

Additional experiments such as current–sampled staircase linear sweep,
differential pulse, normal pulse, square wave, staircase cyclic
voltammetry, and pulse amperometry can be performed with theoptional EChem software — see the EChem Software Manual, or
contact eDAQ for more details.

eDAQ BANK Elektronik Potentiostat Adaptor

17

Introduction
A potentiostat applies a potential difference across a pair of working
and reference electrodes whilst monitoring the current flow between theworking and auxiliary electrodes.
This potential difference is determined by a ‘command voltage’ which issent from the e-corder output to the ‘E In’ connector of the Adaptor,
Figure 2–7. The potentiostat can also generate a constant command
voltage internally, and normally this should be set to zero (or it will be
added to the external command voltage).
Chart and Scope software control the e-corder output via the‘Stimulator’ controls in their Setup menus. For a full description of thesecontrols, and the waveforms that can be produced, you should consult
the Chart Software Manual and Scope Software Manual. You can use
your e-corder and potentiostat with Chart and Scope software to
perform the following experiments:• Linear Scan techniques, page 18 — use Scope software with the
Potentiostat to provide a potential ramp (up to 500 V/s) and to
subtract charging current contributions.
• Chronoamperometry page 21 & page 28, Amperometry, andConstant Potential Electrolysis, — monitor the current signal at fixed
potentials• Chronocoulometry page 31 — monitor and integrate the current
signal at a fixed potentials• Chronopotentiometry , and Constant Current Electrolysis —monitor the potential signal when in Galvanostat mode, page 11, tomaintain a constant current at the working electrode.
• high impedance voltmeter, with some BANK potentiostat models
using ‘–Er’ mode, page 11.

Linear Scan Techniques
Linear sweep or cyclic voltammetry are usually best performed with
EChem software. However, Scope also incorporates Stimulator… andOutput Voltage… commands which can be used to control the analog

18

eDAQ BANK Elektronik Potentiostat Adaptor

output of the e-corder to create a waveform suitable for thesetechniques (albeit less conveniently than with the EChem software).
With Scope software up to 2560 points can be collected on one
channel at a rate of up to up to 100 kHz on both channels.

Fast Cyclic Voltammetry
Scope software has a number of features that can perform Fast Cyclic
Voltammetry (FCV). These are accessed via the Stimulator… and Output
Voltage… commands in the Setup menu, Figure 3–1.
The base potential is set by using the Stimulator Constant Output dialog
box while the waveform is generated using the Stimulator Up & Down,
Figure 3–2, or Triangle, Figure 3–3, waveforms. See the Scope
Software Manual for further details.
In Figure 3–2 the base potential has been set to –1.00 V and apotential ramp has been set up to go from –1.00 to +1.00 V and backagain over a period of 40 ms using the Up & Down waveform option.
This corresponds to a scan rate of 50 V/s.
Figure 3–3 shows an example of a positive and negative cyclic
waveform. The base potential has been set to +0.20 V and a potential
ramp has been set up to go from +0.20 to +0.80 V back again to–0.40 V and finally return to +0.20 V, over a period of 20 ms using
the Triangle waveform option. This corresponds to a scan rate of
120 V/s.
The Triangle waveform option always starts a scan in the centre of thepotential limits, while the Up & Down waveform option starts a scan atone, or the other, of the potential limits.
Ideally, FCV requires a smooth analog ramp, and so it is desirable to
make the steps in the applied waveform output as small as possible.
The e-corder output is controlled by a DAC (digital-to-analog convertor)
is the value of which is updated whenever a new data point acquired.
Thus, by setting the data acquisition rate to be as fast as possible for aparticular experiment, you will also ensure that the waveform has steps
that are as small as possible.
When performing FCV, a large background charging current is often
recorded. This can be many times larger than the signal you are
Chapter 3 — Techniques

19Figure 3–1
Scope Setup menu.

Use the Stimulator… command to access the
Stimulator (applied potential waveform) controls

Use the Output Voltage… command
to set the baseline potential

Figure 3–2
Using the Scope
Stimulator Up and Down
command.

Figure 3–3
Using the Scope
Stimulator Triangle
command.

20

eDAQ BANK Elektronik Potentiostat Adaptor

looking for. Fortunately the charging current is usually reproducible
between scans and can be subtracted from the final result:
1. first a background scan is obtained with a ‘blank’ solution (thatis, a solution containing only the background electrolyte);
2. next a scan is performed of the solution in which the substrate ispresent; and finally
3. the Scope ‘page’ that contains the background scan is selectedusing the Display > Set Background command which will subtract
this scan from all other pages in the file. Use the Display > Don't
Subtract Background command to cancel subtraction, and Clear
Background to cancel the subtraction and clear the backgroundsweep.
The background scan must be run under the same conditions (sweep
width and stimulator settings) as the substrate solution to be effective.
See the Scope Software Manual for more information.

Chronoamperometry with Chart
Chronoamperometric techniques require that a constant potential ismaintained for a defined period while the current is monitored. If thecurrent signal is integrated with respect to time then the total chargetransferred at the electrode can be calculated (Chronocoulometry,page 31).
Single, double and even multi-step chronoamperometry, can be
performed with Chart or Scope software, in a time frame from amillisecond to hours, or even days, if need be. For experiments
involving sudden changes in potential you should use the full bandwidthof the potentiostat (that is do not use low-pass filters) or the response of
the current signal may be modified by the low-pass filter time response
characteristics.

On Windows computers
Chart software can be used to set a constant voltage of up to ±10 V(which is known as the command voltage) from the e-corder Output.
This is sent to the potentiostat, via the ‘E In’ input cable, which thenapplies this potential across the reference and working electrodes. The

Chapter 3 — Techniques

21

software controls are accessed through the Stimulator command in the
Setup menu, Figure 3–4.
To adjust the command voltage you will first need to select the range by
adjusting the Output Range control in the Stimulator controls Figure
3–5. The smaller the selected output range, the finer the control that you
will have when you adjust the potential with the Baseline control. To
monitor the current signal at a constant potential:
1. set the Stimulator to Off;
2. set the Baseline control to the desired voltage;
3. adjust the current input range to an appropriate value, page 14;
4. set the speed of recording (that is the number of data points to becollected per second) to an appropriate value — you will usuallyrequire at least several hundred data points over the lifetime of yourexperiment. The Chart Software Manual has detailed descriptions
on setting the recording speed; and finally
5. begin the experiment by clicking the Start button in the main
Chart window.
The Stimulator command can be used to alter the applied potential witha precision better than 1 ms. Pulses up to 30 s long may be created bythis method. For further details on using the Stimulator in Chart refer tothe Chart Software Manual. An example using the Chart Stimulator isshown in Figure 3–6. Note that the pulse amplitudes are added to any
value set by the Baseline control.
Chart macros can be used to keep the potential constant for a fixed
period of time, or to drive the reaction backwards by first applying one
potential and then subsequently applying a second potential to perform
an oxidation/reduction cycle. Refer to the Chart Software Manual for
more information.

On Macintosh
Chart software can be used to output a constant potential (up to ±10 V)
which the potentiostat will apply at the working electrode. These
controls are accessed through the Setup menu, Figure 3–7.

22

eDAQ BANK Elektronik Potentiostat Adaptor

Figure 3–4
Chart Setup menu(Windows).

Use the Stimulator command to access the Stimulator(applied potential waveform) controls, Figure 3–5 &Figure 3–6

Select stimulator mode

Figure 3–5
Chart Stimulator(waveform output)
controls (Windows).
Select output range
Enter exact values as text.
Use zero amplitude forconstant output
Baseline control canbe used for constant
output — drag slider
controls to adjust
value

Figure 3–6
Stimulator controls for
multiple step
chronoamperometry(Windows).

Settings to produce a 500
mV amplitude 1 Hz squarewave, on a base potentialof –200 mV

Potential waveform generated by
the Stimulator settings above

Chapter 3 — Techniques23

To adjust the potential you will first need to select the range bychoosing the Output Voltage command in the Setup menu to activate
the Stimulator Constant Output dialog box, Figure 3–8. The smaller theselected output range, the finer the control that you will have when you
adjust the potential.
The Timed Events (Setup menu) feature and macros can be used to keep
the potential constant for a fixed period of time, or to drive the reaction
backwards by applying an opposite potential to perform anoxidation/reduction cycle.
The Chart software Stimulator command (in the Setup menu) can also
be used to set up pulses, stepped pulses, and staircase ramp
waveforms for the potentiostat. See the Chart Software Manual for
more details.
You can also use the Timed Events feature (Setup menu) to adjust thecurrent at predetermined time intervals after the start of recording. For
example, the settings shown in Figure 3–9 will maintain a potential of

Figure 3–7
Chart Setup menu
(Macintosh).

Use the Stimulator command to access the
Stimulator (applied potential waveform) controls

Use the Output Voltage… command to
set the baseline potential, Figure 3–8

Figure 3–8
Chart Stimulator
Constant Output voltage
controls (Macintosh).
Select output
range

24

eDAQ BANK Elektronik Potentiostat Adaptor

1.25 V for 30 minutes after which the potential will be decreased to
0.50 V in order to reverse the reaction, resulting in a Double Step
Chronoamperometric experiment. Any number of steps at any potential
could be set up with this feature. However, Timed Events can be slightly
delayed (by up to 0.1 s) depending on the model of computer andwhat else is happening in the computer operating system. For accurate
timing it is better to use the Chart Stimulator which is fully under thecontrol of the internal e-corder clock.
Using the Stimulator command (Setup menu) it is possible to send andmonitor pulses with a precision better than 1 ms, Figure 3–10. Pulses
up to about 30 s may be created by this method. For further details on
using the Stimulator in Chart refer to the Chart Software Manual.

Analysis of Chronoamperometry
Chronoamperomograms obtained from a planar disk electrode should
exhibit a current/time relationship governed by the Cottrell equation,(see Appendix D for definition of terms)
nFAC Di = -----------------------1000 πt

Figure 3–9
Adjusting potential with
the Chart Timed Events
feature. (Macintosh only)

Access Timed Eventsfrom the Setup menu

Chapter 3 — Techniques

Changing the potential
after a period of 30 s

25Figure 3–10
Simulator controls for
multiple step
chronoamperometry(Macintosh).

Stimulator settings to
produce a 500 mV high,
0.5 Hz square wave

Potential waveform generated bythese settings

It is usually easier to first simplify the Cottrell equation thus:ai = ----twhere a is treated as an empirical constant to be determined.
You can use the Chart’s Arithmetic channel calculation (see the Chart
Software Manual) to create ‘data’ on an unused channel (usually
Channel 3) according to the equation:
Channel 3 = 1/Sqrt(SampleTime)You can now use the X–Y window to plot the current signal (usually on
Channel 1) versus Channel 3, and a near straight line should beobtained with a slope of a, Figure 3–11.
With the Curve Fit extension installed, you can use the Curve Fittingcommand (Windows menu) to fit your current signal data with an
idealised curve. The Curve Fit analysis extension and accompanying
documentation can be downloaded free from the eDAQ web site,www.eDAQ.com. The extension file should be put into the Chart
Extensions folder, inside the Chart folder on your hard disk.

26

eDAQ BANK Elektronik Potentiostat Adaptor

Figure 3–11
Typicalchronoamperometricdata, analyzed using theArithmetic channel
calculation and the X–Y
window.

Typical experiment with1/√t data calculated on
Channel 3 using theArithmetic channel

Region of ideal linear
response
Cottrell graph of current versus
1/√t prepared in the XY
Window. Deviations fromlinearity typically occur at verysmall and very large t values.

It is unlikely that the current signal will decay to exactly zero (due toconvection currents in the vessel causing non-ideal diffusion) so a small
non-zero constant, b, is added. Also the equation is very sensitive to theexact instant when t is zero which is a problem if you have selected
data very close to zero time (in the Curve Fitting window, it is usually
best to use the ‘t=0 at start of block’ option as shown in Figure 3–12).
In this case, to get a well behaved equation when the data selectedstart at very close to zero time, initially add a small time correction, c.
This allows for the errors in the estimation of time zero, and the fact that
the Potentiostat has a finite bandwidth (and so the current signal will

Chapter 3 — Techniques27take a small amount of time to register a true value after a suddenchange in potential).
Thus a better form of the equation to be fitted is:ai = -------------- + b
t+cThis must be entered as a New Equation in the Curve Fit extension thevery first time you use it, Figure 3–12.
Because of the discontinuity that occurs when the denominator is zero,
first try fixing c to a small positive value, and iterating for better valuesof a and b. Some trial and error will be involved while you makeguesses that are suitable for the initial values to iterate. After the better
estimates for a and b have been determined, and iterated, c can be
unlocked so that it refines during the next iteration, Figure 3–12.
Your data selection should not include points very close to zero time(the Potentiostat will require some time to settle), nor points taken atvery long times when convection aided diffusion will produce non-ideal
behaviour. The exact time period that is suitable will depend on thesize of the electrode, and some trial and error to determine the timeinterval to give best results will probably be required.
After the file is saved, the Curve Fit Cottrell equation will be available
whenever you open Chart data file on the same computer or even when
you transfer the data file to another computer on which Chart softwareand the Curve Fit extension are installed.

Chronoamperometry with Scope
For chronoamperometric measurements, where you need to overlay the
results of successive experiments, Scope will generally be the programof choice.
The total length of the experiment is chosen in the Time Base panel. Up
to 2560 data points can be collected in a period of up to 128 s long.
You should normally use the full bandwidth of the potentiostat (that is,
do not use any low-pass filters) or the response of the current signal
may be dominated by the low-pass filter time response characteristics.

28

eDAQ BANK Elektronik Potentiostat Adaptor

Figure 3–12
Fitting a Cottrell equation
to data with the Curve Fit
extension.

At the time of writing theCurve Fit extension is
only available for Chartfor Macintosh.

Define the Cottrell
relationship as a newequationFirst lock in a value for c, thentry guesses for a and b until anapproximate fit is obtained

Usually use ‘t=0
at start of block’

Iterate by clicking the Fit button, refining a
and b only. If the initial guesses are closeenough, then a curve of better fit with newvales for a and b will be obtained.

Unlock c, and iterate again. A curveof best fit should be obtained.

Chapter 3 — Techniques

29

The base potential is adjusted with the Output Voltage… command(Setup menu) shown in Figure 3–13.
A potential that will cause the reaction to proceed (and the period forwhich it will be applied) is set using the Stimulator command. In theexample shown in Figure 3–13, after a period of 10 s at the basepotential of +0.5 V, two 30 s pulses of –0.70 V are to be applied eachfollowed by a 30 s return to the base potential.
The experiment is usually first done on a blank solution containing only
electrolyte, followed by a sample solution containing the substrate. The
data is collected on separate pages in Scope and the ‘blank’ datasubtracted with the Set Background command. You can then copy andpaste the scan to a spreadsheet so that the differences can be plottedagainst 1/√t in a Cottrell graph.
For further details refer to the Scope Software Manual.

Use the Stimulator… command to access the
Stimulator (applied potential waveform) controls

Figure 3–13
Scope controls for
multiple step
chronoamperometry.
Use the Output
Voltage…
command to set thebaseline potential

Adjust the pulse
waveform
duration,
amplitude andfrequency

30

eDAQ BANK Elektronik Potentiostat Adaptor

Chronocoulometry
Chart and Scope software have the ability to integrate an incoming
signal both online (that is, in real time as you are collecting data), or
offline (that is after the experiment is completed). Since the total chargetransferred (the total number of coulombs, or electrons, transferred) is
equal to the integrated current, the settings used forchronoamperometry, page 21, can also be used for chronocoulometry.
With Chart software it also necessary to set up an unused channel(usually Channel 3) to be the integral of the current signal channel(usually Channel 1).
With an online function you need to actually be recording data toobtain the integral. To configure Channel 3 you need to choose theComputed Input command from the Channel Function pop-up menu,
which opens the Computed Input dialog box (Figure 3–14 on a
Windows computer, and Figure 3–15 on a Macintosh). For more
information refer to the Computed Input section in the Chart Software
Manual.
Post-acquisition integration of a signal is also possible with the Chart
Integral channel calculation, which is accessed via the Integral
command in the Channel Function pop-up menu — further details are in
the Chart Software Manual. This is particularly useful when you want torecalculate the integral from the original current signal. The real time
methods will give good results only if the appropriate sensitivity range
has been pre-selected — and it is not always possible to determine thisbeforehand. A good strategy is often to use the real time integral
function to get an idea of what is happening during an experiment andthe use post-acquisition integration to prepare data for a final report.
With Scope software the current signal can be integrated by using theComputed Functions… command, Figure 3–16. The Integrate item ischosen from the Function menu. This is actually a post-acquisition
function — you can always cancel it afterwards to look at theunderlying current data. Refer to the Scope Software Manual for more
information.

Chapter 3 — Techniques

31

Figure 3–14
Online integration of thecurrent signal using
Chart Computed Input
integration (Windows).

Figure 3–15
Online integration of thecurrent signal using
Chart Computed Input
integration (Macintosh).

Figure 3–16
Integration of the current
signal using Scope
Computed Functions.

Select Integrate in the Function menu

32

eDAQ BANK Elektronik Potentiostat Adaptor

A

P

P

E

N

D

I

X

A Troubleshooting

A

This appendix describes some problems that may arise. There is also
help in your e-corder Manual and Software Manuals, located on theeDAQ Software Installer CD.
In many cases, a problem can be fixed by turning the e-corder andcomputer off, checking that all cables are are firmly attached, andstarting again. If you cannot correct the problem, then please contact
your eDAQ representative.
The Adaptor On–line indicator fails to light when the software is
opened.
• Check that the e-corder is connected to the mains power and that
it is turned on.
• Check that Adaptor is properly connected to the e-corder and thatthe cables are not loose. Especially check that the ‘E in, ‘I Out’ and‘E Out’ cables are correctly connected, see page 7.
• If possible, change cables and try again. If a second cable works
and you find that the first cable is faulty, you should contact eDAQ
for a replacement.
• If you are using EChem software, check that the ‘E In’ cable isconnected to the e-corder output and the ‘I Out’ and ‘E Out’ cables
are connected to e-corder Input 1 and 2, see page 7.
• Try using the Adaptor with another e-corder (if available). If theOnline indicator fails to light on the second e-corder, the Adaptor orits cables may be faulty — contact eDAQ. If it works correctly on aeDAQ BANK Elektronik Potentiostat Adaptor

33

second e-corder then the first e-corder may be faulty — contact
eDAQ.
The ‘Bank Elektronik’ controls cannot be accessed in Chart, Scope orEChem software (that is only the standard ‘Input Amplifier’ dialog boxof the e-corder can be accessed)• Check that the Adaptor Online indicator is illuminated after thesoftware has been opened. If not, then proceed as in the previous
problem.
• Check that you have connected the ‘E In’, ‘I Out’ and ‘E Out’cables correctly to the appropriate e-corder connectors.
The Potentiostat Overload indicator is on (a potential overload has
occurred).
• Check that the electrode cables are firmly attached to theelectrodes.
• Check that the surfaces of the electrodes have not become fouled.
The current signal goes off scale.
• Increase the full scale current range setting.
• Make sure each electrode is connected to the correct potentiostat
lead.
• Make sure the electrodes and their lead wire contacts are nottouching each other.
• Decrease the surface area of your working electrode.
• Decrease the concentration of the background electrolyte.
• Decrease the concentration of the substrate.
• Check that a potential overload (see previous section) has notoccurred.
The results show peaks or steps at the inverse polarity I expect to see(i.e. a peak may be occurring at 0.5 V when it should be at –0.5 V).
• Check that you are connected to the correct Output (+ or –) of thee-corder. See Connecting the Adaptor, page 8.

34

eDAQ BANK Elektronik Potentiostat Adaptor• If you are using Chart or Scope, software check that the Invert box
is checked or not, as appropriate, for the potential recording
channel.
The results show peaks (or steps) at different potentials than you expect.
• See previous section.
• Make sure the reference electrode is connected to the correct
potentiostat lead wire. Connection of the reference electrode toeither the working or auxiliary leads can cause rapid electrodedeterioration requiring electrode replacement.
• Check the condition of the reference electrode. All referenceelectrodes age. For example and Ag/AgCl electrode will age with
exposure to light. Eventually the white/light grey coating of AgCl on
the central silver wire will be replaced by a brown/black coating ofsilver oxide. As this process takes place the apparent positions ofyour voltammetric peaks will appear to shift to different potentials.
Most Ag/AgCl electrodes can be quickly regenerated by placing
the silver wire in 1 M hydrochloric acid solution for a minute or two(any silver oxide is quickly reconverted to AgCl), although you may
wish to remove the old coating completely and re–chloridize thesilver wire to ensure a good coating of fresh AgCl. In either casereplace the newly coated wire back into the electrode casing withfreshly prepared KCl solution. Aged calomel (Hg/Hg2Cl2)electrodes
should usually be replaced. Reference electrodes using a gelled
electrolyte will deteriorate if the gel dries out.
The results show peaks in the negative current direction when you wantthem in positive direction.
• Check that the Invert box is checked or not, as appropriate, forthe current recording channel. See Inverting the Signal, page 15.
The results show peaks (or steps) at different potentials than you expect.
• See previous section.
• Make sure the reference electrode is connected to the correct
potentiostat lead wire!
• Check the condition of the reference electrode. All referenceelectrodes age. For example and Ag/AgCl electrode will age with

Appendix A — Troubleshooting

35

exposure to light. Eventually the white/light grey coating of AgCl on
the central silver wire will be replaced by a brown/black coating ofsilver oxide. As this process takes place the apparent positions ofyour voltammetric peaks will appear to shift to different potentials.
Most Ag/AgCl electrodes can be quickly regenerated by placing
the silver wire in 1 M hydrochloric acid solution for a minute or two(any silver oxide is quickly reconverted to AgCl) — although you
may wish to remove the old coating completely and re–chloridize
the silver wire to ensure a good coating of fresh AgCl. Replace the
newly coated wire back into the electrode housing and refill withfreshly prepared KCl solution. Aged calomel (Hg/Hg2Cl2)electrodes should usually be replaced. Reference electrodes using agelled electrolyte will deteriorate if the gel dries out.
The results are contaminated by ‘noise’.
• Most often the noise encountered in electrochemical experiments
is a manifestation of mains hum (50 or 60 Hz interference) frompower lines and mains–powered equipment. Note that, dependingon the sampling rate, aliasing can make such interference appear
as a low frequency oscillation superimposed on your data. Ensurecommon grounding by attaching the e-corder and computer to thesame power board which is then attached to a three pin (grounded)
power socket. If consistent with the bandwidth required by yourexperiment, use a 10 Hz (or lower) filter of to record your results.
Get an electrical technician to check that the grounding of thepower socket itself is in good condition. Try the Mains Filter setting(Chart and Scope software) which is very effective at removing main
induced artifacts• Check electrode connections. Poor electrical contact to theelectrodes will act as a source of noise. Particularly check theelectrode cables: cables age, especially at the connectors where
they are subject to mechanical wear.
• Ensure that the reaction vessel (and electrodes) are positioned as
far as possible from power leads, computers, monitors and othermains–powered equipment. Ideally the reaction vessel should be
enclosed by a Faraday cage. A Faraday cage (or other electricalshielding) is almost always required when measuring small currents.
• Random spikes occurring during your experiment are more likely
to be due to nearby electrical equipment switching on and off.
Equipment with high current drain such as electric motors in vacuum

36

eDAQ BANK Elektronik Potentiostat Adaptor

pumps, refrigerators, or air–conditioner compressors should beparticularly suspect. Try turning such equipment off during yourexperiment to identify the source of the problem. You may have tochange your location (try a power socket on another circuit in thesame room, or even move rooms completely).

Appendix A — Troubleshooting

37

38

eDAQ BANK Elektronik Potentiostat Adaptor

A

P

P

E

N

D

I

B Specifications

X

B

Control Ports
Analog signals:

Three female BNC, for E In, I Out andE Out.

I2C input and output:

Male and female DB-9 pin connectors.
Provides control and power to the
Adaptor.

Potentiostat Interface:

Female DB-25 pin connector. Provides
digital I/O control over the potentiostat.

Power requirements:±17 V DC
+8 V DC
25 mA typical
2W

Physical Configuration
Dimensions (h × w × d):

54 × 105 × 167 mm
2.1 × 4.1 × 6.6 inches

Weight:0.42 kg (0.93 lb)

Operating conditions:0 – 35˚C
0 – 90% humidity (non-condensing)eDAQ reserves the right to alter these specifications at any time.

eDAQ BANK Elektronik Potentiostat Adaptor

39

40

eDAQ BANK Elektronik Potentiostat Adaptor

BANK Potentiostat Adaptor
EA169

On-line

Scan

Index

A

D

amperometry 17

differential pulse voltammetry 17

Applied Current
Potentiostat/Galvanostat 16

E

Applied Potential
Potentiostat 15

E In connector 7

B

EChem software 17

back panel
Potentiostat 7
BANK Potentiostat
compatible models 1C
C4D Amp 2

E Out connector 7eDAQ Amps 2
C4D Amp 2
GP Amp 2
Picostat 2
Potentiostat 2
Quad pH Amp 2
Quad Tc Amp 2
QuadStat 2–Er mode 11

checking procedure 3
chronoamperometry 21
analysis 25
Chart
Macintosh 22
Windows computers 21
multiple step 23, 26, 30
Scope 28
chronocoulometry 31

Ffast cyclic voltammetry 18, 19
fast linear sweep voltammetry 18
front panel 6

G

Cottrell equation 25, 30

Galvanostat mode 11, 18

curve fitting 26

GP Amp 2

cyclic voltammetry 17, 19

eDAQ BANK Elektronik Potentiostat Adaptor

41

I
I Out connector 7
I2C connector 7
input amplifier 10

Quad Tc Amp 2
QuadStat 2

R

Interface Control Window 11

Real cell
Potentiostat 15

L

reference electrodeaging and regeneration 35

linear scan techniques 18
linear sweep voltammetry 17

M
Mains Filter 36
mains hum 36
Model selection 11
Modes of operation
Potentiostat, Galvanostat, –Er 11
multiple step chronoamperometry 23, 26, 30

Nnoise 36
normal pulse voltammetry 17

O
Online indicator 6

S
Scan indicator 6
square wave voltammetry 17
Standby cell
Potentiostat 15

T
Timed Events 24

Vvoltammetry
cyclic 17
differential pulse 17
fast cyclic 18, 19
fast linear sweep 18
linear sweep 17
normal pulse 17
square wave 17

P
Picostat 2
polarity 9
potentiostat
Model selection 11
Potentiostat (EA161) 2
Potentiostat Interface port 8
Potentiostat mode 11
problems 33
pulsed amperometry 17

Q
Quad pH Amp 2

42

eDAQ BANK Elektronik Potentiostat Adaptor

BANK Potentiostat Adaptor
EA169

On-lineScan

License & Warranty

Trademarks
e-corder and PowerChrom are registeredtrademarks of eDAQ Pty Ltd. All eDAQ software,
hardware, and documentation is protected bycopyright. eDAQ retains the exclusive ownership of
the trademarks and registered trademarks
represented by its company name, logo, andproduct names.

Responsibilities
You and any others using any eDAQ product agree
to use it in a sensible manner for purposes for which
it is suited, and agree to take responsibility for theiractions and the results of their actions.
If problems arise with an eDAQ product, eDAQ will
make all reasonable efforts to fix them. This service
may incur a charge, depending on the nature of the
problems, and is subject to the other conditions inthis Agreement.

Hardware Warranty
eDAQ Pty Ltd warrants eDAQ hardware, to be freeof defects in material and workmanship for one year
from the date of purchase. eDAQ Pty Ltd will repair
or replace defective equipment as appropriate.
To obtain a warranty repair/replacement you mustfirst notify us before return of the instrument and wewill issue you with a RAN (return authorizationeDAQ BANK Elektronik Potentiostat Adaptor

number). You must ship the defective product at yourexpense. We will pay return shipping. The productshould be packed safely (preferably in its original
packaging) and have the RAN on the shippinglabel. Returns sent without a RAN may be refuseddelivery.
This warranty does not cover hardware that has:• been modified by the user in any way;
• been subjected to unusual physical, electrical,
or environmental stress. This includes damage
due to faulty power sockets, inadequate
earthing, or power spikes or surges;• been damaged because of incorrect wiring toancillary equipment, or because of substandard,connectors or cables; or• had the original identification marks removed
or altered.

Software License
You have the non-exclusive right to use suppliedeDAQ software (Chart, Scope etc). Your employees
or students, for example, are entitled to use it,provided they adhere to this agreement. Eachseparate purchase of the eDAQ software licenses it
to be used on two computers at any given time (onone computer for data acquisition with a e-corder
hardware unit, and on a second computer for the
analysis of existing data files). Although multiple
copies of a program may exist on several

43

computers, more than two copies must not be usedsimultaneously. Departmental/company licences areavailable if you wish to run more than two copies
simultaneously.

Technical Support
Please register your unit to receive technical support.
Technical assistance is available via email. Please
describe the problem with as much detail as
possible. Include a small example data file, if
appropriate. Please also state:• the model and serial number of your e-corderunit and Potentiostat Adaptor.
• the type of computer and operating systembeing used (for example Windows XP, or
Macintosh OS 10.2)• the software version you are using (forexample Chart v5.1.2)
We endeavor to answer all your questions, but insome cases, for example where the problem relates
to the other equipment that you are using, a nominal
fee may be charged.

Jurisdiction
eDAQ Pty Ltd is bound by the laws of New South
Wales in Australia, and any proceedings shall beheard by the Supreme Court of New South Wales inAustralia.

Disclaimer
eDAQ reserves the right to alter specifications ofhardware and software without notice.
No liability can be accepted for consequential
damages resulting from use of eDAQ products.

44

eDAQ BANK Elektronik Potentiostat Adaptor