Potentiostat & Picostat User Manual

Potentiostat& Picostat
Overload

Potentiostat

Overload

Picostate-corder®

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 of data
recording units, such as e-corder 201, andPowerChrom 280, are trademarks of eDAQ Pty Ltd.
Chart and Scope are trademarks of ADInstruments
Pty Ltd and are used under license by eDAQ.
EChem is a trademark of eDAQ Pty Ltd.

Products: Potentiostat (EA160); Picostat (EA162)
Document Number: UM-EA160/162-1203
Copyright © December 2003
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

Potentiostat & Picostat Owner’s Guide

OverloadPotentiostat

Contents

1 Overview 1
How to Use this Manual 2eDAQ Amps 2
Checking the Potentiostat or Picostat 3

2 The Potentiostat 5
The Front Panel 6
The Input Connector 6
Electrode Cable 7
The Online Indicator 7
The Overload Indicator 7
The Back Panel 8
Multiport Connector 8
Connecting the Potentiostat 9First Use 12
Potentiostat Control Window 14
Maintenance 18

3 The Picostat 19
The Front Panel 20
Input Connector 20
Electrode Cable 21
The Online Indicator 21
The Overload Indicator 22
The Back Panel 23
E Out, I Out and E In Connectors 23
I2C Connectors 23
Potentiostat & Picostat

Grounding Connector 24
Connecting the Picostat 25
First Use 27
Picostat Control Window 30
Maintenance 33

4 Techniques 35
Introduction 36
Linear Scan Techniques 36
Fast Cyclic Voltammetry 37
Chronoamperometry with Chart 39
On Windows computers 39
On Macintosh 40
Analysis of Chronoamperometry 43
Chronoamperometry with Scope 48
Chronocoulometry 49
Chronopotentiometry 51
Chart software on Windows computers 52
Chart software on Macintosh 54
Scope software 56
Controlled Potential Electrolysis 56
Controlled Current Electrolysis 57
Amperometric Sensors 58
Biosensors 59
Microdialysis Sensor 59
Dissolved Oxygen (dO2) Sensors 59
Nitric Oxide (NO) Sensors 60

iii

A Technical Aspects 63
Potentiostat 63
Picostat 65

B Troubleshooting 67
C Specifications 73
Potentiostat 73
Picostat 75

D Electrochemical Equations 77
Linear Sweep and Cyclic
Voltammetry 77
Chronoamperometry 79
Chronocoulometry 80

Index 81
License & Warranty 85

iv

Potentiostat & Picostat

C H A P T E R

1 Overview

O N E

The eDAQ Potentiostat and Picostat can perform various
electrochemical voltammetric and amperometric experiments. They area part of a family of fully–software controlled modular preamplifiers(eDAQ Amps) which are designed for use with the e-corder® system.
Many of the additional uses of the Potentiostat and Picostat forelectroanalytical chemistry are described in the EChem Software
Manual which describes the use of the optional EChem software.

Potentiostat & Picostat

1How to Use this ManualThis manual describes how to set up and begin using your Potentiostat(Chapter 2) or Picostat (Chapter 3). Their use with Chart and Scope
software is also described (Chapter 4). The appendices provide
technical and troubleshooting information. See the EChem Software
Manual for a description of the use of the Potentiostat and Picostat withthe optional EChem software.

eDAQ Amps
The Potentiostat and Picostat are part of a family of preamplifiers
known as eDAQ Amps.
The Potentiostat and Picostat are designed for performing voltammetricand amperometric experiments. As with other eDAQ Amps, they aredesigned 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 also includes the:•pH Amp, suitable for connection of pH, ion selective, andpotentiometric (ORP) electrodes•

Bridge Amp, suitable for sensors requiring a DC Wheatstonebridge connection. Also provides DC excitation•

GP Amp, suitable for high output sensors requiring a highimpedance DC Wheatstone bridge. Also provides DC excitation.

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

2

Potentiostat & Picostat

Checking the Potentiostat or
Picostat
Before you begin working with the Potentiostat or Picostat, please checkthat:• 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 on the
Installer CD.

Chapter 1 — Overview

3

4

Potentiostat & Picostat

C H A P T E R

T W O

2 The Potentiostat

This chapter describes how to connect and use your Potentiostat.
IMPORTANT: Always make sure that the e-corder is turned off before
you connect or disconnect the Potentiostat. Failure to do this may resultin damage to the e-corder and/or the Potentiostat.

Potentiostat & Picostat

5

The Front Panel
The front panel of the Potentiostat is shown in Figure 2–1.

The Input Connector
The input connector of the Potentiostat provides connection pins for theWorking, Auxiliary and Reference electrodes. The connector also
provides connections for the lead shields which protect the signals in
the cable wiring from electrical interference (noise pickup).
The pin assignments of the Potentiostat input connector are shown in
Figure 2–2. The Auxiliary and Reference electrode leads have coaxial
shields which are maintained at the respective electrode potential.

Figure 2–1
The Potentiostat front
panel.

Overload
indicator light

Input connector,
DIN socket,
to electrodes

Overload

Potentiostat

Online indicator light

5. Working electrode

Figure 2–2
The Potentiostat input
connector as seen whenlooking at the front
panel.

2. Chassis ground

4. Working electrode

3. Auxiliary electrode shield

7. Auxiliary electrode8. Not connected

1. Reference electrode shield
Chassis ground
6. Reference electrode

6

Potentiostat & Picostat

Table 2–1
Color–coding on theleads of the electrodecable.

Color

Electrode

Yellow

Reference

Green

Working

Red

Auxiliary

Electrode Cable
The Potentiostat is supplied with an electrode cable comprising threeleads, with each lead terminated by an alligator clip. The Reference
and Working electrode leads are shielded to protect the signals fromexternal interference. The alligator clips allow connection to a wide
variety of electrodes, and the leads are color–coded to indicate thetype of electrode to which they should be attached (Table 2–1).
For normal three–electrode use, the reference electrode must never beconnected to either the auxiliary (red) or working (green) leads,
otherwise the current that would be passed through the electrode could
effectively destroy it as a reference potential source.
If two-electrode operation is required the auxiliary and referenceelectrode leads (red and yellow) should be attached to the single‘counter electrode’. The green electrode lead is attached to the working
electrode.

The Online Indicator
Located at the bottom right of the front panel is the Online indicator.,
Figure 2–1. When lit, it indicates that the software (such as EChem,
Chart or Scope) has located and initialised the Potentiostat. If the light
does not go on when the software is run, check that the Potentiostat isproperly connected. If there is still a problem, please refer to Appendix
B B, page 67.

The Overload Indicator
Located on the left-hand side of the front panel is the Overload
indicator, Figure 2–1. When lit, this indicates that the Potentiostat is out

Chapter 2 — The Potentiostat7

of compliance, which usually occurs because of an open circuit orexcessive resistance in the electrochemical cell. Higher resistances canbe often be encountered when electrodes are fouled by the products ofelectrolysis reactions. The Potentiostat tries to compensate by increasing
the compliance potential (that is, the potential between the auxiliary
and working electrodes). If the compliance voltage exceeds
specification (about 11 V) potential control of the cell is lost anddrifting, or oscillation, of the signal can be seen. Any data collectedduring this period is unreliable and should be discarded.
The Overload indicator will light when there is an overload and will goout once the overload is removed.
If the indicator light comes on repeatedly, and your connections are
good, then try bringing your electrodes closer together, and/or
increasing electrolyte concentration, and/or modifying yourexperimental conditions to avoid fouling of the electrodes. Redesigning
your electrochemical cell may be necessary. Normally cells aredesigned to keep the reference and working electrodes very close
together, however, when a potential overload occurs, you also need toconsider the distance between the auxiliary and working electrodes.
Note that a potential overload is quite different from a current overload
condition. A current overload is caused when the current signal
exceeds the full scale limits of the range setting of the current channel,
and is usually caused by a low resistance between the electrodes.

The Back Panel
The back panel of the Potentiostat is shown in Figure 2–3.

Multiport Connector
The Potentiostat back panel has a single ‘Multiport’ 24 pin connector
that connects it to the e-corder. A cable is provided with the Potentiostat
for this purpose. This connection provides power to the Potentiostat andcarries the various analog and control (gain range and filter settings)
signals between the two. The pin assignments of the Multiport are
shown in Figure 2–4.
8

Potentiostat & Picostat

Figure 2–3
The Potentiostat backpanel.
Multiport

Multiport connector,
Centronics 24 pin,
12C, power, and analog
input and outputs

12

1

24

13

Figure 2–4
The Potentiostat Multiportpin assignments.

1 Not connected
2 SDA (I2C control)
3 SCL (I2C control)
4 Not connected
5 Not connected
6 MPDSD (I2C control)
7 DSC (I2C control)
8 Not connected

9 Not connected
10 Analog ground
11 Digital ground
12 Not connected
13 Regulated +8 V
14 Not connected
15 Not connected
16 E Out, analog signal

17 I Out, analog signal
18 Not connected
19 Not connected
20 Not connected
21 Not connected
22 Regulated +17 V
23 Regulated –17 V
24 E In, analog signal

Connecting the Potentiostat
Your Potentiostat will have been supplied with a cable that is terminatedby a ‘Multiport’ (Centronics 24 pin) connector at one end and, at theother end, terminated by a I2C (DB-9 pin) connector and three BNC
connectors.
First make sure that the e-corder is turned off. Connect the Multiport endof the cable to the matching connector on the rear panel of the
Potentiostat.

Chapter 2 — The Potentiostat

9

Table 2–2
Potentiostat to e-corderconnections.

Table 2–3
Potentiostat to e-corderconnections, reverse
polarity.

Cable labelled

e-corder front panel

CH1 (I) or I Out

Input 1CH2 (E) or E Out

Input 2OUTPUT (E In)

Output –Cable labelled

e-corder front panel

CH1 (I) or I Out

Input 1CH2 (E) or E Out

Input 2OUTPUT (E In)

Output +Connect the other end of the cable to the I2C connector on the rear
panel of the e-corder. Use the three BNC terminated cables to connect
to the front panel of the e-corder as shown in Table 2–2.
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 2–5 and Figure 2–6.
To operate the Potentiostat with the reverse polarity make theconnections as shown in Table 2–3.
With these connections, when you use the software to set a morepositive voltage, a more reducing potential will be applied at theworking electrode.
Check that all connectors are firmly attached. Loose connectors cancause erratic behaviour, or may cause the Potentiostat to fail to work.
The Potentiostat uses two e-corder input channels during normal
operation. The reminder of this chapter assumes that you haveconnected the current signal to e-corder Input Channel 1 and thepotential signal to e-corder Input Channel 2. (It is possible when using
Chart or Scope software to connect the Potentiostat to other e-corder
10

Potentiostat & Picostat

Figure 2–5
The Potentiostat shown
connected to an
e-corder, front view.

Overload

Potentiostat

Input 1401

Input 2

Input 3

Power
Status

OutputInput 4

Trigger

Figure 2–6
The Potentiostat shown
connected to an
e-corder, back view.

input channels, in which case the 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 Input Channel 1, andthe potential signal (E Out) to Input Channel 2 of the e-corder.
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.
Chapter 2 — The Potentiostat

11

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 Potentiostat as described above, you areready to begin.
When the e-corder is turned on, and Chart software started, thePotentiostat Online indicator (green) should light.
From the Channel 1 Function pop-up menu, select the ‘Potentiostat’command, which opens the Potentiostat Control window, Figure 2–7(Windows), or Figure 2–8 (Macintosh).
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 ‘Potentiostat’ then the software has notrecognised the Potentiostat. Exit the software, check all yourconnections and try again).
By default, the control window opens with the Potentiostat in Standby
mode, that is with the reference and working electrodes isolated so thatno current will flow 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.
Now select Dummy mode operation. You will need to adjust the gain
range to 20 µA to accommodate your signal amplitude. You can now
adjust the applied potential with the slider bar, or by entering the exact
potential with the A-button. The resulting current signal should obey
Ohm’s law:
I = E/Rso that an applied potential of 1 V should produce a current of 10 µA,
while other potential settings should produce corresponding currents.

12

Potentiostat & Picostat

Figure 2–7
Accessing the
Potentiostat controls with
Chart software(Windows).

Pause/resume scrolling

Drag ticks and labels toadjust axis scaling
Select input
range
Select lowpass filter
Set mainsfilterSignal display
area

SelectPotentiostat in
the Channel 1
pop-up menu

Invert signal
Select cellmode
Selectpotentiostat
orgalvanostat
operation

Select range
for applied
potential

Remember applied
potential

Slider bar for setting
applied potential

Enter applied
potential as text

Select Potentiostat in the
Channel pop-up menu

Figure 2–8
Accessing the
Potentiostat controls with
Chart software(Macintosh).

Drag ticks andlabels to adjust axis

Select cellmode

Select input
range

Select lowpass filter

Selectpotentiostat
orgalvanostat
mode

Signal display area

Enter
AppliedPotential
Slider bar
for setting
appliedpotential
Pause/Resume
scrolling

Chapter 2 — The Potentiostat

Axis expansion/
contraction

Invert signal

Set mains filter

13

Potentiostat Control Window
With Chart software, the Potentiostat Control window is accessed fromthe Potentiostat command in the Channel Function pop-up menu. Figure
2–7 shows the control window on a Windows computer, and Figure
2–8 on a Macintosh computer. These windows control the various
current ranges and filtering options for the Potentiostat.
With Scope software, the corresponding controls are shown in Figure
2–9.

Potentiostat/Galvanostat Operation
The Potentiostat can be operated in either potentiostat (Chart, Scope orEChem software) or galvanostat mode (Chart and Scope software only)
by selecting the appropriate radio button.

Figure 2–9
Accessing the
Potentiostat controls with
Scope software.

Use the Potentiostat button
Pause/Resume
scrolling

Select input
range

Select lowpass filter
Selectpotentiostat
orgalvanostat
mode

Signal display area

Set
AppliedPotential
Set mainsfilterDrag ticks andlabels to adjust axis

14

Axis expansion/
contraction

Select cell
mode

Invert signal

Potentiostat & Picostat

The rest of this chapter deals with potentiostatic operation. The use ofgalvanostat mode is dealt with on page 52 – 56.

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 is lost.
By using the Dummy or Real modes the effect of an applied potential
can be seen.
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 — similar to the amplitude axis in themain Chart, Scope or EChem window. All changes made in the
Potentiostat Control window are reflected in Chart, Scope or EChemand vice versa.

Setting the Range
Use the Range pop-up menu to select the input current range (channel
sensitivity). The Potentiostat has ranges of 100 mA to 20 nA, while
resolution within each range is 16 bits or 0.0015%. You should set therange so that it is larger than the biggest current that you expect toencounter during your experiment. If, during the experiment the current
signal exceeds the range, then the signal will go off scale and thosedata points effectively lost.

Filtering
The Potentiostat incorporates four low-pass filters at 10 kHz, 1 kHz,
100 Hz and 10 Hz for removal of high frequency signals (‘noise’). In
addition the e-corder provides filter settings at 1, 2, 5, 20, 50, 200,
500, and 2000 Hz (Chart software on Windows computers).
As a general rule the 10 Hz filter setting is highly effective for theremoval of mains hum (50 or 60 Hz interference) and should be
employed whenever possible. However, it should not be used for pulse

Chapter 2 — The Potentiostat

15

amperometric or voltammetric experiments where the pulses are shorter
than 100 ms, or for experiments where rapid scan rates (greater thanabout 100 mV/s) are used, or else the signal you collect may be
excessively smoothed.
In addition, with Chart and Scope software, there is a 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. Notethat the mains filter is not a notch filter, and can remove a 50 or 60 Hz
interference even if it is not a pure sinusoidal function. However, themains filter does take a few seconds to ‘learn’ the pattern of theinterference so that you will need to record for longer than this for it totake full effect. The mains filter can be employed even for experiments
in which there are sudden potential jumps.

Inverting the Signal
The Invert checkbox, allows you to invert the incoming signal. It
provides a simple way to reassign the directions (up or down) of ananodic (or cathodic) current. Please note that this affects the display ofthe signal only — it does not reverse the direction of actual current flowat the electrodes!

Cell Control
The Potentiostat can be in one of three operating modes, controlled by
the Cell radio buttons:• Standby: If Standby mode is selected the electrode lead wires are
disconnected (With the Potentiostat the internal dummy cell isconnected). The external cell is not connected until the Potentiostat
Control window is closed and the Chart, Scope or EChem Start
button is clicked. This mode is used if you do not wish to alter thestate of the external cell until the method is actually performed. The
Applied Potential slider bar control is disabled in this mode.
• Dummy: When Dummy mode is selected the Potentiostat isconnected to the internal 100 kΩ dummy cell. You can then use theApplied Potential slider control to vary the voltage applied to thedummy cell. The Potentiostat will remain connected to the dummycell even when the Potentiostat Control window is closed and Chart,

16

Potentiostat & Picostat

Scope or EChem is recording. This is useful for testing the
Potentiostat.
• Real: In Real mode the external electrodes are connected to the
Potentiostat while the Potentiostat Control window is open, Figure
2–7 and Figure 2–8. The Applied Potential slider control can beused to set the potential applied to the electrodes. When you closethe 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 are using Chart or Scope software, the Potentiostat
will remain in Real mode when the dialog is closed — this allows
you to start and stop recording data while the electrodes remain
active, which allows periodic recording of the signal fromamperometric biosensors or in vivo electrodes without disturbing theenvironment around the electrodes.

Applied Potential
The applied potential slider control is enabled in either Dummy or Realmodes. It allows you to adjust the voltage applied to either the dummycell or external electrodes, depending on the mode selected.

Excitation Range
When using Chart software on a Windows computer you have theoption of limiting the range over which the applied potential can be set.
Smaller ranges offer finer control with the slider bar, or text entry,of theapplied potential, Figure 2–7.
On a Macintosh computer use the Range control in the Stimulator
Constant Output dialog box, Figure 4–8, page 42.

Remember Potential
When using Chart software you can check the box labelled ‘Set
applied potential as baseline…’ This causes the potential set with theslider bar or text entry to be transferred to the Stimulator baseline
control when the window is closed.

Chapter 2 — The Potentiostat

17

MaintenanceYour Potentiostat will not require maintenance during daily operation.
However, you should periodically check the Potentiostat for optimum
results by applying a known potential, E, to the Dummy Cell andchecking that the resulting current signal, I, is in accordance with
Ohm’s law:
I = E/R
where R is the resistance, and is 105 Ω for the dummy cell. Thus asignal of 10 µA should be obtained when a potential of 1 V is applied.
Try several different potentials and make sure an appropriate current
signal is observed. If this test produces the expected results then yourPotentiostat is likely to be functioning correctly and if you areexperiencing difficulties with your experiments then you should now
check the electrode cables.
Attach the electrode cables to a resistor (usually a resistor of
103–106 Ω is ideal) with the working electrode lead on one side andthe auxiliary and reference leads connected to the other side. If thecurrent signal does not obey Ohm’s law, then it is likely that theelectrode leads have become damaged. However, if this test produces
the expected results, but you are experiencing difficulties with yourexperiments, then you should now check the electrodes you are using,and the design and condition of the reaction vessel, and any salt
bridges that you are using.

18

Potentiostat & Picostat

C H A P T E R

3 The Picostat

T H R E E

This chapter describes how to connect and use your Picostat (EA162).
IMPORTANT: Always make sure that the e-corder is turned off before
you connect or disconnect the Picostat. Failure to do this may result indamage to the e-corder and/or the Picostat.
IMPORTANT: The Picostat is a highly sensitive current measuring device.
To prevent damage by static discharge always make sure you areearthed before touching the Picostat input connector, connecting thelead wires, or before you connect the lead wire alligator clips to theelectrodes. You can do this (after first connecting the Picostat ande-corder) by touching the outer casing of the e-corder or Picostat. This
will connect you to earth (via the electrical grounding of the instrument)
and any static charge you have collected will be dissipated.

Potentiostat & Picostat

19

The Front Panel
The front panel of the Picostat is shown in Figure 3–1.

Input Connector
The Input connector of the Picostat provides connection pins for theWorking, Auxiliary and Reference electrodes. The connector also
provides connections for shields which protect the signals in the cablewiring from electrical interference (noise pickup).
The pin assignments of the Picostat Input connector are shown in Figure
3–2. The Working and Reference electrode leads have coaxial shields
which are maintained at the respective electrode potentials to minimise
lead capacitance.

Figure 3–1
The Picostat front panel.
Overload
indicator light

Input connector,
6 pin Lemo socket,
to electrodes

Overload

Picostat

Online indicator light

Alignment dot

Figure 3–2
The Picostat input
connector as seen whenlooking at the front
panel.

Working Electrode

Working Electrode Shield

Auxiliary ElectrodeNot connected

Reference Electrode
Reference Electrode Shield

20

Potentiostat & Picostat

Table 3–1
Color-coding on theleads of the electrodecable.

Color

Electrode

Yellow

Reference

Green

Working

Red

Auxiliary

Electrode Cable
The Picostat is supplied with a three lead electrode cable, with eachlead terminated by an alligator clip. The Reference and Working
electrode leads are shielded to protect the signals from externalinterference. The alligator clips allow connection to a wide variety ofelectrodes. The leads are color-coded to indicate the type of electrodeto which they should be attached (Table 3–1).
For normal three-electrode use, the reference electrode must never beconnected to either the auxiliary or working leads, otherwise the current
that would be passed through the reference electrode could effectively
destroy it as a reference potential source.
If two-electrode operation is required the auxiliary and referenceelectrode leads (red and yellow) can be attached to the single ‘counterelectrode’. The green electrode lead is attached to the working
electrode.
When attaching the cable to the Picostat make sure that the red dot on
the cable connector is aligned with the red dot on the Picostat Input
Connector, Figure 3–2. Insert the cable connector and push gently until
it locks into position. To remove the cable pull the cable connector
gently until it disengages. Do NOT twist the connector.

The Online Indicator
Located at the bottom right of the front panel is the Online indicator,
Figure 3–1. When lit, it indicates that the software (such as EChem,
Chart or Scope) has located and initialised the Picostat. If the light does
not go on when the software is run, check that the Picostat is properly
connected. If there is still a problem, please refer to Appendix B
Troubleshooting, page 67.
Chapter 3 — The Picostat

21

The Overload Indicator
Located on the left–hand side of the front panel is the Overload
indicator, Figure 3–1. When lit, this indicates that the Picostat has goneout of compliance, which usually occurs because of an open circuit(such as an unconnected or faulty electrode) or the resistance is toohigh in the electrochemical cell. Higher resistances can be often be
encountered when electrodes are fouled by the products of electrolysis
reactions. The Picostat tries to compensate by increasing thecompliance potential (that is, the potential between the auxiliary andworking electrodes). If the compliance voltage exceeds specification,
about 13 V, potential control of the cell is lost and drifting, oroscillation, of the signal can be seen. Any data collected during thisperiod is unreliable and should be discarded.
The Picostat Overload indicator will remain lit once an overload has
occurred — it will be reset once the scan has finished.
If the indicator comes on repeatedly, and your connections are good,then try bringing your electrodes closer together, and/or increasing
electrolyte concentration, and/or modifying your experimental
conditions to avoid fouling of the electrodes. Redesigning you
electrochemical cell may be necessary. Normally electrochemical cells
are designed to keep the reference and working electrodes very close
together, however, when a potential overload occurs, you also need toconsider the distance between the auxiliary and working electrodes.
NOTE: A potential overload is quite different from a current overload
condition. A current overload is caused when the current signal
exceeds the full scale limits of the sensitivity setting of the current
channel. This is, in turn, due to a low resistance between the electrodes.

22

Potentiostat & Picostat

Figure 3–3
The Picostat back panel.

BNC output
connectors
E Out

BNC input
connector

I Out

E In

4 mm socket,
ground connection

2

Input

I C
Bus

OutputDB-9 pin, I2C connectors

The Back Panel
The back panel of the Picostat is shown in Figure 3–3.

E Out, I Out and E In Connectors
The Picostat back panel has three BNC connectors labelled E Out,I Out, and E In. The E In is connected to the Output of the e-corder,
usually Output – (or Output 2 on SP e-corders) is used. If you need toreverse the polarity of the Picostat use e-corder Output +.
The Picostat provides two signals: the potential signal (E Out) indicating
the potential difference between the working and reference electrodes;
and the current signal (I Out) indicating the current flow between theworking and auxiliary electrodes.
For most situations I Out is connected to e-corder input channel 1, andE Out to e-corder input channel 2. However, when you are using Chart
software and recording data from various sources on more that just twochannels you may want to connect the Picostat to other e-corder input
channels.

I2C Connectors
The Picostat back panel, Figure 3–3, has two DB-9 pin ‘I2C bus’
connectors labelled Input and Output. The Input connector provides

Chapter 3 — The Picostat

23

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

▲ WARNING!
The I2C connectors arefor the power andcontrol of eDAQ Ampsand should not be
used for connection to
any other device.

Regulated +17 V DC
Regulated +8 V DC

I2C control signals

Figure 3–4
The pin assignments for
the Input I2C DB-9
connectors.

1

5

5

1

6

9

9

6

Input

Outputpower to the Picostat and carries the various control signals (for gain
range and filter selection) to and from the e-corder connection to thee-corder. A cable is provided with the Picostat for this purpose. The pin
assignments are shown in Figure 3–4.
The Output connector can be used for the attachment of other eDAQ
Amps.
More information about the I2C connector can be found in youre-corder Manual.

Grounding Connector
The Picostat back panel, Figure 3–3, has a 4 mm grounding socket.
This enables connection of a Faraday cage (with the green grounding
cable included with the Picostat) the use of which can greatly diminish
electrical noise. The construction of the Faraday cage can range from a
simple cardboard box covered with aluminium foil, in which theelectrochemical cell is located, to a more sophisticated copper meshenclosure or sheet-metal box.
In all cases, it is essential that the Faraday cage be electricallygrounded to act as an effective shield against electrical interference.
The Picostat is supplied with a green colored ground cable terminatedwith a 4 mm pin (attaches to Picostat back panel) and an alligator clip(for attachment to Faraday cage) for this purpose. The Picostat itself isgrounded via its connection to the e-corder unit which is in turn earthed

24

Potentiostat & Picostat

via the three pin mains power connector. It is of course important thatthe power socket that you are using is well earthed.
The purpose of this ground cable to the Faraday cage is to provide aneasy means of grounding the cage — please note that it is not forgrounding the Picostat. If your Faraday cage is already earthed by its
own ground connection then you should not use this cable! Use of thecable in this instance will provide a second pathway to earth which
could result in a ‘ground loop’ which can actually increase signal
interference! You can try grounding the Faraday cage via its own
connection to earth, or via the Picostat ground cable — but not by bothmethods simultaneously.

Connecting the Picostat
Your Picostat will have been supplied with an I2C cable (DB–9 pin
connectors at either end), and three cables with BNC connectors ateither end.
First make sure that the e-corder is turned off. Then connect the I2C
cable to the I2C connector on the back panel of the e-corder, and theother the other end to the I2C Input connector on the back panel of thePicostat. Use the three BNC cables to connect the back panel of thePicostat to the front panel of the e-corder as in Table 3–2.

Table 3–2
Picostat to e-corder BNC
connections.

Table 3–3
Picostat to e-corder BNC
connections, reverse
polarity.

Chapter 3 — The Picostat

Picostat rear panel

e-corder front panel

I Out

Input 1E Out

Input 2

E In

Output –Picostat rear panel

e-corder front panel

I Out

Input 1E Out

Input 2

E In

Output +25

Figure 3–5
The Picostat shown
connected to an
e-corder, front view.

Overload

Picostat

Input 1401

Input 2

Input 3

Power
Status

OutputInput 4

Trigger

Figure 3–6
The Picostat shown
connected to an
e-corder, back view.

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 3–5 andFigure 3–6.
To operate the Picostat with the reverse polarity make the connections
shown in Table 3–3.
With these connections, when you use the software to set a morepositive voltage, a more reducing potential will be applied at theworking electrode.

26

Potentiostat & Picostat

Check that all connectors are firmly attached. Loose connectors cancause erratic behaviour, or may cause the Picostat to fail to work.
The Picostat uses two e-corder input channels during normal operation.
The reminder of this chapter assumes that you have connected thecurrent signal to e-corder Input Channel 1 and the potential signal toe-corder Input Channel 2. (It is possible when using Chart or Scope
software to connect the Picostat to other e-corder input channels inwhich case the 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 Input Channel 1, andthe potential signal (E Out) to Input Channel 2, of the e-corder.
Channel 2 normally displays the applied potential and its settings arecontrolled using the standard Input Amplifier dialog box, described in
the Chart and Scope Software Manuals on the eDAQ Installer CD.

First Use
After you have installed the software, connected the e-corder andcomputer as described in the booklet that is supplied with the e-cordersystem, and connected the Picostat as described above, you are readyto begin.
When the e-corder is turned on, and Chart software started, the Picostat
Online indicator (green) should light. Touch the body of the Picostat or
e-corder (to discharge any static charge that you may haveaccumulated), then attach the 100 MΩ test resistor (supplied with thePicostat) to the electrode leads so that the Working electrode lead isconnected to one end of the resistor, and Reference and Auxiliaryelectrode leads to the other).
From the Channel 1 Function pop-up menu, select the ‘Picostat’command, which accesses the Picostat control window, Figure 3–7,
Figure 3–8, or Figure 3–9.
The Picostat control window allows you to preview the current signal
without actually recording the signal to the computer hard disk. (If the

Chapter 3 — The Picostat

27

Figure 3–7
Accessing the Picostat
controls with Chart
software (Windows).

Current signal Drag ticks and labels
display area to adjust axis scaling

Start/stop scrolling
Select input
range
Select lowpass filter
Set mainsfilterInvert signal
Select Realor Standby
mode

Select Picostat fromthe Channel 1
Function pop-up
menu

Select range for Remember applied
applied potential potential

Figure 3–8
Accessing the Picostat
controls with Chart
software (Macintosh).

Slider bar for setting Enter applied
applied potential
potential as text

Select Picostat from the Channel 1
Function pop-up menu

Drag ticks andlabels to adjust axis

Select input
range
Select lowpass filter
Select Realor Standby
mode

Current signal
display area

Enter
AppliedPotential
Slider bar
for setting
appliedpotential

Pause/Resume
scrolling

28

Axis expansion/
contraction

Invert signal

Set mains filter

Potentiostat & Picostat

menu says ‘Input Amplifier’ instead of ‘Picostat’ then the software has
not recognised the Picostat. Exit the software, check all yourconnections and try again).
By default, the control window opens with the Picostat in Standby
mode, that is with the reference and working electrodes isolated so thatno current will flow through your electrodes. To connect to the Picostat
lead wires you must select Real mode. When you click Cancel or OK
the Picostat will revert to Standby mode until recording is started.
You will need to adjust the gain range to 20 nA to accommodate yoursignal amplitude, and to select the 10 Hz low-pass filter (and/or Mains
Filter) to minimise high frequency noise on the signal — especially if
you are working outside a Faraday cage.
You can now adjust the applied potential with the slider bar, or byentering the exact potential with text entry. The resulting current signal
should obey Ohm’s law:
I = E/R

Figure 3–9
Accessing the Picostat
controls with Scope
software.

Use the Picostat button
Pause/Resume
scrolling

Select input
range

Select lowpass filter
Signal display area

Set
AppliedPotential
Set mainsfilterDrag ticks andlabels to adjust axis

Chapter 3 — The Picostat

Axis expansion/
contraction

Select cell
mode

Invert signal

29

so that with the 100 MΩ test resistor, R, in place, an applied potential,
E, of 1 V should produce a current, I, of 10 nA, while other potential
settings should produce corresponding currents.

Picostat Control Window
With Chart software, the Picostat Control window is accessed from thePicostat command in the Channel Function pop-up menu. Figure 3–7
shows the control window on a Windows computer, and Figure 3–8 on
a Macintosh computer. These windows control the various current
ranges and filtering options for the Picostat.
With Scope software, the corresponding controls are shown in Figure
3–9.

Signal Display
The current signal is previewed scrolling across the display area. Notethat the signal is not being recorded to hard disk at this stage, and thatwhen the window is closed the signal trace is lost.
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. All changes to axis scaling are reflectedin the Chart and Scope main window, and vice versa.

Setting the Range
The Range pop-up menu lets you select the input current range orsensitivity. The Picostat has ranges of 10 pA to 100 nA (if you require asystem to monitor larger currents, the Potentiostat has ranges of 20 nA
to 100 mA). You should set the range so that it is larger than the
biggest current that you expect to encounter during your experiment. If,
during the experiment the current signal exceeds the range, then thedata will be truncated and therefore lost.

30

Potentiostat & Picostat

Filtering
The Picostat has an internal 10 Hz low-pass filter for removal of highfrequency signals (‘noise’). The Off setting gives the full bandwidth of
the Picostat which can be up to 16 kHz (but which may also be limitedby the characteristics of your electrodes and sample solution).
The 10 Hz filter setting is highly effective for the removal of mains hum(50 or 60 Hz interference) and, as a general rule, should be employedwhenever possible. However, it should not be used for either pulse
amperometric or voltammetric experiments where the pulses are shorter
than 100 ms, or for voltammetric experiments where fast scan rates(greater than 100 mV/s) are used, or for other signals which are likely
to exhibit fast rise or fall times — otherwise excessive smoothing of thesignal may occur.
In addition, with Chart and Scope software, there is a 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. Notethat the mains filter is not a notch filter, and can remove 50 or 60 Hz
interference even if it is not a pure sinusoidal function. However, themains filter does take a few seconds to ‘learn’ the pattern of theinterference so that you will need to record for longer than this for it totake full effect. The mains filter can be employed even for experiments
in which there are sudden potential jumps.

Inverting the Signal
The Invert checkbox allows you to invert the incoming current signal. It
provides a simple way to redefine the directions (up or down) of ananodic (or cathodic) current signal. This control does not affect thedirection of current flow at the electrodes.

Cell Control
The Picostat can be in one of two operating modes, controlled by the
Cell radio buttons:• Standby: If Standby mode is selected the auxiliary and referenceelectrodes are isolated by an internal relay which effectively meansthat all the electrodes are at a ‘floating’ potential and that no current

Chapter 3 — The Picostat

31

will be passed through your experimental solution. The electrodes
will not be connected until the Picostat control dialog is closed andthe Chart, Scope or EChem Start button is clicked to begin a scan.
The Applied Potential control is disabled in this mode.
• Real: In Real mode the electrodes will be active and the Applied
Potential slider control can be used to adjust the potential. When
you close the control dialog (using EChem or Scope software) the
Picostat will revert to Standby mode until the Start button is clicked to
begin a scan. If you are using Chart or Scope software, the Picostat
will remain in Real mode when the dialog is closed — this allows
you to start and stop recording data while the electrodes remain
active, which allows periodic recording of the signal fromamperometric biosensors or in vivo electrodes without disturbing theenvironment around the electrodes.

Applied Potential
The applied potential slider control is only enabled in Real mode. It
allows you to adjust the voltage applied to the electrodes. To change
the value simply drag the control left or right to set an appropriate
potential, or use the text entry controls to enter a numerical value.
When using Chart software on a Windows computer the default
potential will be the same as the Baseline value in the Stimulator
control.

Excitation Range
When using Chart software on a Windows computer you have theoption of limiting the range over which the applied potential can be set.
Smaller ranges offer finer control with the slider bar or text entry of theapplied potential.
On a Macintosh computer use the range control in the Stimulator
Constant Output dialog box, Figure 4–8.

Remember Potential
When using Chart software on a Windows computer you can select thecheckbox labelled ‘Set applied potential as baseline…’ This causes thepotential set with the slider bar or text entry to be transferred to the
Stimulator baseline control when the window is closed.

32

Potentiostat & Picostat

MaintenanceYour Picostat will not require maintenance during daily operation.
However, you should periodically check the Picostat for optimum
results.
First set up the Picostat and e-corder as outlined earlier in this Chapter.
Disconnect the electrode cable from the Picostat. Open the Picostat
Control window, Figure 3–7 or Figure 3–8. Adjust the current range to
10 pA, the Low Pass filter to 10 Hz, and select Real mode. After acouple of seconds the resulting current signal should have stabilised
and be close to zero. If the current signal is drifting significantly, or isgreater than ±5 pA, then contact your eDAQ representative — it ispossible that stray static discharge may have damaged the Picostat’s
electrometer chip.
Also periodically repeat this procedure with the electrode cableconnected, and attached to the 100 MΩ test resistor, as described in
the section on First Use, page 27. If the current signal does not obey
Ohm’s law, then first recheck your connections of the Picostat to thee-corder, page 25. If the problem persists then it is possible that theelectrode leads or the Picostat itself has become damaged.
If these tests indicate that the Picostat is working correctly, but you arestill experiencing difficulties with your experiments, then you should
now check the electrodes you are using, the connections to them, andthe design and condition of the reaction vessel, and any salt bridges
that you are using.

Chapter 3 — The Picostat

33

34

Potentiostat & Picostat

C H A P T E R

4 Techniques

F O U RThe Chart and Scope software supplied with your e-corder can be used
to perform many different electrochemical techniques with the
Potentiostat and Picostat. This chapter provides an overview of thesetechniques, but you will need to also refer to the Chart Software
Manual and Scope Software Manual (which are installed on thecomputer hard disk, with the software, or can be found on the eDAQ
Installer CD).
Also discussed is the use of the Potentiostat when configured as agalvanostat.
Additional experiments such as current–sampled staircase linear sweep,
differential pulse, normal pulse, square wave and cyclic voltammetry,and pulse amperometry can be performed with the optional EChemsoftware — see the EChem Software Manual, or contact eDAQ for
more details.

Potentiostat & Picostat

35

Introduction
The Potentiostat and Picostat apply a potential difference across a pairof working and reference electrodes whilst monitoring the current flow
between the working and auxiliary electrodes.
The potential difference is determined by a ‘command voltage’ which issent from the e-corder output to the ‘E In’ connector of the Picostat,
Figure 3–3, on page 23, or the E in pin of the Multiport connector of
the Potentiostat, Figure 2–4, on page 9. Chart and Scope software
control the e-corder output via the ‘Stimulator’ controls in their Setup
menus. For a full description of these controls, and the waveforms thatcan be produced, you should consult the Chart Software Manual andScope Software Manual.
You can use your e-corder and Potentiostat, or Picostat, with Chart andScope software to perform the following experiments:• Linear Scan techniques — use Scope software with the Potentiostat
to provide a potential ramp (up to 500 V/s) and to subtract
charging current contributions. The bandwidth of the Picostat is
sufficient for scan rates up to about 10 V/s• Chronoamperometry, Amperometry, Constant Potential Electrolysis— monitor the current signal at fixed potentials• Chronocoulometry — monitor and integrate the current signal at a
fixed potentials• Chronopotentiometry, Constant Current Electrolysis — monitor the
potential signal when the Potentiostat is used as a galvanostat tomaintain a constant current at the working electrode• Monitoring of amperometric sensors including dissolved oxygenand nitric oxide electrodes.

Linear Scan Techniques
Linear sweep or cyclic voltammetry are usually best performed with
EChem software. However, Scope incorporates Stimulator… andOutput Voltage… commands which can be used to control the analog
output of the e-corder to create a waveform suitable for driving thePicostat or Potentiostat. With Scope software up to 2560 points can be
36

Potentiostat & Picostat

collected on one channel at a rate of up to up to 100 kHz on bothchannels.

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 4–1.
The base potential is set by using the Stimulator Constant Output dialog
box while the waveform is generated using the Stimulator Up & Down,
Figure 4–2, or Triangle, Figure 4–3, waveforms. See the Scope
Software Manual for further details.
In Figure 4–2 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 4–3 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 4 — Techniques

37

Figure 4–1
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 4–2
Using the Scope
Stimulator Up and Down
command.

Figure 4–3
Using the Scope
Stimulator Triangle
command.

38

Potentiostat & Picostat

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 49).
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 or Picostat (that is, if possible, do not use the lowpass 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 Picostat or Potentiostat via the ‘E In’ input cable,
which then applies this potential across the reference and working

Chapter 4 — Techniques39electrodes. The software controls are accessed through the Stimulator
command in the Setup menu, Figure 4–4.
To adjust the command voltage you will first need to select the range by
adjusting the Output Range control in the Stimulator controls Figure
4–5. 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 Pulse mode;
2. set the Pulse Amplitude to zero volts;
3. set the Baseline control to the desired voltage;
4. adjust the current input range to an appropriate value, page 15
and page 30;
5. 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
6. 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 4–6. 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 Picostat or Potentiostat will apply at the working electrode.
These controls are accessed through the Setup menu, Figure 4–7.

40

Potentiostat & Picostat

Figure 4–4
Chart Setup menu(Windows).

Use the Stimulator command to access the Stimulator(applied potential waveform) controls, Figure 4–5 &Figure 4–6

Select stimulator mode

Figure 4–5
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 4–6
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 4 — Techniques41

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 4–8. 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 or Picostat. 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 4–9 will maintain a potential of

Figure 4–7
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 4–8

Figure 4–8
Chart Stimulator
Constant Output voltage
controls (Macintosh).

Select output
range
Click the A-button
for text entry

Drag the slider control to adjust
the output

42

Potentiostat & Picostat

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 4–10. 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 4–9
Adjusting potential with
the Chart Timed Events
feature. (Macintosh only)

Access Timed Eventsfrom the Setup menu

Chapter 4 — Techniques

Changing the potential
after a period of 30 s

43Figure 4–10
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 4–11.
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.

44

Potentiostat & Picostat

Figure 4–11
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. This can be 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 4–12).
To get a well behaved equation when the data selected start at very
close to zero time it is usually best to initially add a small timecorrection, c, which will allow for the errors in the estimation of timezero, and the fact that the Potentiostat has a finite bandwidth and so

Chapter 4 — Techniques

45the current signal will take a small amount of time to register a true
value after a sudden change 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 4–12.
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 4–12.
Also your data selection should not include points very close to zerotime (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 the quality of the Potentiostat, and some trial
and error to determine the time interval 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.
Remember to operate the Potentiostat or Picostat at full bandwidth (thatis do not use the low-pass filters if possible) or else your results may be
dominated by the low-pass filter response!

46

Potentiostat & Picostat

Figure 4–12
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 4 — Techniques47

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 or
Picostat (that is, do not use the low-pass filters) or the response of thecurrent signal may be dominated by the low-pass filter time response
characteristics. The base potential is adjusted with the Output Voltage…
command (Setup menu) shown in Figure 4–13.
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 4–13, after a period of 10 s at the base

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

Figure 4–13
Scope controls for
multiple step
chronoamperometry.
Use the Output
Voltage…
command to set thebaseline potential

Adjust the pulse
waveform
duration,
amplitude andfrequency

48

Potentiostat & Picostat

potential 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.

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 39, 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 4–14 on a
Windows computer, and Figure 4–15 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

Chapter 4 — Techniques

49

Figure 4–14
Online integration of thecurrent signal using
Chart Computed Input
integration (Windows).

Figure 4–15
Online integration of thecurrent signal using
Chart Computed Input
integration (Macintosh).

Figure 4–16
Integration of the current
signal using Scope
Computed Functions.

Select Integrate in the Function menu

50

Potentiostat & Picostat

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 4–16. 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.

Chronopotentiometry
Chronopotentiometry requires that a constant current be maintained
between the working and auxiliary (counter) electrodes. The potential at
the working electrode is monitored. For many systems the potential willremain approximately constant until the electroactive species isconsumed, after which there will be a sudden change in the potential.
For this type of experiment it will be necessary to run the Potentiostat in
Galvanostat mode with Chart or Scope software. For correct operation
make sure that the ‘CH 1 (I)’ cable of the Potentiostat is connected to
Input 1 of the e-corder, and the ‘CH2 (E)’ cable of the Potentiostat isconnected to Input 2.
Note that galvanostat mode is not available with the Picostat.
When using the Potentiostat as a galvanostat, the applied current canbe set within ranges up to 100 mA. Select the smallest range setting
consistent with your desired current to ensure maximum accuracy. For
example, if a current of 750 µA is required then a range setting of
1 mA (1000 µA) should be used, and then exact current value adjusted
accordingly.
The current values used should ensure that the resulting potentials do
not exceed ±10 V (the maximum limit of the Potentiostat) — highly
resistive loads can easily produce large potentials, even with small
currents.
Remember that when setting zero, or very small, currents there isalways a small amount of offset (error) in the system. If you are trying tomeasure the potential of a system under zero current conditions then it

Chapter 4 — Techniques51

would generally be more accurate to use a zero current potentiometer(or pH meter) than a galvanostat.

Chart software on Windows computers
To switch to the Galvanostat mode of operation, choose the Potentiostat
command in the Channel Function pop-up menu to open the control
window, and turn on the Galvanostat and Dummy radio buttons, Figure
4–17.
When in Galvanostat mode, the current and potential signals will bereversed from normal (potentiostatic) operation. That is, the ‘I Out’Figure 4–17
Setting up the
Potentiostat as a
Galvanostat (Windows).

Select Potentiostat in
the Channel menu
Potential signal is displayedwhen in Galvanostat mode

Select the expected range
for the potential signal

Select Galvanostat
current range

Access the Current
channel units
conversion dialog, tFigure 4–18
The Current channel units
conversion dialog box.

52

Set appliedcurrent (within
the range setting)Select galvanostat
operation

Use these values to set
Units Conversion for
the Current channel

Potentiostat & Picostat

Figure 4–19
The Chart Stimulator
dialog box when the
Potentiostat is in
Galvanostat mode

When in Galvanostat
mode the Stimulator
controls are used toadjust the appliedcurrent.Compare withPotentiostat mode where
the Stimulator is used toadjust applied potential,
Figure 4–6.

cable will be carrying the potential signal (which will now appear on
Channel 1) and the ‘E Out’ cable the current signal (which will now
appear on Channel 2). You will need to configure the Units Conversionof Channel 2 so as to ensure that the current signal is recorded in thecorrect current units, Figure 4–18.
When the Chart Stimulator command (Setup menu) is selected it
accesses the Stimulator dialog box which, when using galvanostat
mode, allows a baseline and various current waveforms to be
configured, Figure 4–19.
Always select an appropriate current range for your system. While it ispossible to set an applied current of up to 100 mA, the Potentiostat/
Galvanostat cannot supply a potential much greater than ±10 V. Even
relatively small applied currents, with a highly resistive load, may
require potentials in excess of this. If in doubt, start with a small test
current and observe the resulting potential.
Using a large range setting with a small (close to zero) current can
produce unexpected results (large potential signals) with highly resistive
loads because of small offsets in the current control circuitry. If you
require very small currents always use a small range setting as well, thiswill ensure a minimum offset error. For example, to apply a current of
only 25 nA use the 100 nA range setting for best results.

Chapter 4 — Techniques

53

Figure 4–20
Setting up the
Potentiostat as a
Galvanostat (Macintosh).

Select Potentiostat in
the Channel menu

Select the expected range
for the potential signal
Select galvanostat
operation

Potential signal isdisplayed when in
Galvanostat modeSetappliedcurrent

The four Galvanostat current range settings inthis menu, are dependent on the e-corder
Output Voltage range, Table 4–1, on page 55

Chart software on Macintosh
To switch to the Galvanostat mode of operation, choose the Potentiostat
command in the Channel Function pop-up menu to open the control
window, and turn on the Galvanostat and Dummy radio buttons, Figure
4–20.
When in Galvanostat mode, the current and potential signals will bereversed from normal (potentiostatic) operation. That is, the ‘I Out’cable will be carrying the potential signal (which will now appear on
Channel 1) and the ‘E Out’ cable the current signal (which will now
appear on Channel 2). When you start to record data you will find that
the Units Conversion on Channel 2 has been set to appropriate value
so that the signal is automatically displayed with the correct current
units.
The default setting is to have the applied current on the 100 mA range.
It is likely that there will be a small residual offset at this setting which

54

Potentiostat & Picostat

Table 4–1
Galvanostat current
range settings of the
Potentiostat as a functionof e-corder output range.

e-corder Output
Voltage Range

Potentiostat/Galvanostat primary gain
100 nA/V

1 µA/V

100 µA/V

10 mA/V

10 V

1 µA

10 µA

1 mA

100 mA

5V

500 nA

5 µA

500 µA

50 mA

2V

200 nA

2 µA

200 µA

20 mA

1V

100 nA

1 µA *

100 µA

10 mA

500 mV

50 nA

500 nA *

50 µA

5 mA

200 mV

20 nA

200 nA *

20 µA

2 mA

* It is better to use the corresponding settings with the 100 nA/V primary gain.

will cause the Potentiostat/ Galvanostat to go off scale (over 10 V) in
Standby mode (as it is connected to the relatively low resistance 105 Ωinternal dummy cell). Try selecting a more appropriate 1 µA or 10 µA
range, where the offset will be correspondingly smaller, and the signal
should come on screen and be close to zero volts.
The e-corder Output Voltage can be set as described earlier, Figure
4–8, on page 42. At each of these Output Voltage range settings the
Potentiostat offers four current range settings when in Galvanostat
mode, Table 4–1. The most accurate control is achieved by using thelargest possible Output Voltage range with the smallest possible
Galvanostat range setting.
You can use the slider bar, or the text entry to adjust the current within
the selected range. The resulting potential signal is shown in the display
area.
You control the current passed by the Potentiostat/ Galvanostat byadjusting the Output Voltage controls (Setup menu) — this adjusts the
e-corder control voltage which is reinterpreted as a current value by the
Potentiostat/ Galvanostat. For example, if you have selected an
e-corder Output Voltage range of 500 mV, and a current range of
50 µA xxx, you might now wish to do an experiment where the current
is held at a constant 35 µA (or 35/50 × 100 = 70% of the range
setting). You should now set the slider control of the Output Voltage
control to a value of 70% of 500 mV, that is to 350 mV. A positive or

Chapter 4 — Techniques

55negative Output Voltage determines the direction of current flow (into or
out of the working electrode).
The Chart software Stimulator command (Setup menu) can also be used
to set up pulses, stepped pulses, and staircase ramp waveforms which
the galvanostat will follow. You can also use the Timed Events feature(Setup menu) to adjust the current at predetermined time intervals after
the start of recording.
Consult the Chart Software Manual for more details of the Output
Voltage, Stimulator, and Timed Events features.

Scope software
Operation of the Potentiostat as a Galvanostat with Scope software issimilar to using Chart software (Macintosh version), see page 54.
However, a wider variety of applied waveforms can be generated with
the Scope Stimulator command.

Controlled Potential Electrolysis
This technique is essentially the same as Chronoamperometry with
Chart, page 39, and is also known as amperometry. A constantpotential is applied at the working electrode which is sufficient tooxidize or reduce the substrate. As the electrolysis continues thesubstrate is eventually completely consumed and the current will
decrease to a residual value. Both the potential and the current flow
can be monitored with Chart software in the same way as forchronoamperometry. The integrated current (that is, the total chargetransferred) can also be determined by integrating the current signal(see Chronocoulometry, page 49) and this can be used to determine
the extent of reaction.
If the solution is being stirred during the procedure then eventually all
the substrate can be oxidized, or reduced, to a new material and thetechnique may be referred to as electrosynthesis rather thanchronoamperometry.
If the reaction causes the formation of a polymer film on the electrode(for example pyrrole to polypyrrole, or aniline to polyaniline) then thetechnique may be referred to as electropolymerisation.

56

Potentiostat & Picostat

A potential should be chosen which is at least 50 – 200 mV moreoxidising (or reducing) than the half-wave potential of the substrate inorder to ensure complete reaction. It is usually important to separate theauxiliary (counter) electrode from the main body of the electrochemicalcell by means of a salt bridge. This is to prevent the reduction productsin the region of the auxiliary electrode reacting with the products ofoxidation at the working electrode (or if reducing the substrate, toprevent the products of oxidation forming around the auxiliaryelectrode from reacting with the reduction products at the working
electrode). The working electrode is usually constructed to haverelatively large surface area so that a greater amount of material canbe electrolyzed in a small time — thus a plate or gauze electrode isusually chosen, although reticulated vitreous carbon (RVC) which has
an open pore foam structure, is also a popular choice.
The conversion of large amounts of substrate (> 100 mg) in reasonable
times requires relatively high currents to be passed through the cell.
Thus the Potentiostat (maximum current 100 mA) is usually moresuitable than the Picostat (maximum current 100 nA) for
electrosynthesis. The production of organic compounds in highly
resistive non-aqueous solvents often requires the addition of large
amounts of electrolyte to sustain the current flow (and which can lead todifficulties in later separation of the product). For studies using water, orother protic solvent, the addition of a small quantity of acid (or base)can increase the conductivity of the cell greatly, without having to add
large amounts of electrolyte.

Controlled Current Electrolysis
These techniques are essentially the same as Chronopotentiometry,page 51, and require the use of a galvanostat. The Potentiostat, when
operated in Galvanostat mode, is suitable for experiments where
currents less than 100 mA and potentials less than 10 V are
anticipated. (Please note that the Picostat cannot be operated as agalvanostat). A constant current is applied between the working andauxiliary electrodes and the potential at the working electrode ismonitored as the substrate is oxidized or reduced. As the electrolysis
continues the substrate is eventually completely consumed and thepotential will alter as the galvanostat tries to maintain a constantcurrent. Both the potential and the current flow can be monitored with
Chart software. The integrated current (that is, the total charge

Chapter 4 — Techniques57transferred) can also be determined which can be used to determine
the extent of reaction.
Electrosynthesis and electropolymerization reactions are often more
quickly carried out under constant current conditions than underconstant potential conditions, but there is a greater risk of side reactions
occurring as the potential changes. Ideally there should no competing
redox reactions at nearby potentials.
A sudden change in the potential usually indicates when the substrate is
fully consumed.
It is important to limit the current so that the potential stays within thecompliance voltage (10 V) of the Potentiostat/Galvanostat, at least until
the reaction of interest is complete. Electropolymerization reactions canbe problematic as a non-conducting polymer film adhering to theworking electrode will increase its electrical resistance causing the
Potentiostat to eventually go out of compliance and experience a
potential overload.

Amperometric Sensors
Amperometric sensors require a potentiostat of appropriate gain range.
Your will also need to determine whether the sensor is of a two or threeelectrode configuration. Both the Potentiostat (currents greater than
100 nA) and Picostat (currents less than 100 nA) can be used in threeelectrode mode (working, reference and auxiliary electrode), or in twoelectrode mode (working and counter electrodes) by connecting thereference and auxiliary leads of the electrode cable together. You will
also need to determine the correct ‘polarising voltage’ to use with yoursensor. The ‘polarising voltage’ is the potential at which the Potentiostat
or Picostat applies at the working electrode.
Normally Chart software (rather than Scope) is the better choice ofrecording software for these types of sensor. The Units Conversion
feature of Chart can be used to perform two point calibration of thesignal in the units of your choice, which is satisfactory for most uses —see the Chart Software Manual for more information. If multiple point,
or non-–linear, calibration is required then the Chart Multiple Point
Calibration extension can be used with up to 12 calibration points. You

58

Potentiostat & Picostat

can download the extension and accompanying documentation fromthe eDAQ web site at www.eDAQ.com.
If the experiment requires a differential pulse methodology then the
MuliPulse Amperometry techniques of the EChem software can be usedfor various pulse amperometric experiments. See the EChem Software
Manual for more details.

Biosensors
Biosensors are often amperometric sensors and so can be used with thePicostat or Potentiostat which can used as ‘biosensor meters’. The firststep is to establish the polarising voltage and current measurement
requirements of your sensor.
Many biosensors provide a linear signal response over a limited rangeof concentrations. The Chart software Multiple Point Calibration
extension can be used to extend the useful range over which abiosensor can be used by compensating for a non-linear signal
response.

Microdialysis Sensor
The Sycopel™ Microdialysis Biosensor is available in several
configurations for both in vivo or in vitro detection of analytes including
glutamate, glucose, glycerol, ascorbate and acetylcholine. The Picostat
has suitable current ranges for use with this sensor, and Chart software
would normally be used to record data.

Dissolved Oxygen (dO2) Sensors
Usually a polarographic (Clark) oxygen sensor electrode and meter arepurchased from the same manufacturer to ensure matching sensitivity.
However, depending on the current requirements of your oxygen
sensor, either the Potentiostat or Picostat may be a suitable alternative
to a standard meter as they have adjustable sensitivity and can bematched to a wide range of current signal requirements. In addition
you can use them to alter the polarising voltage to ‘fine tune’ yoursensor.

Chapter 4 — Techniques

59

Most polarographic oxygen electrodes comprise a gold or platinum
cathodic working electrode (to which the working electrode lead is
attached) and a silver anodic counter electrode (to which the reference
and auxiliary electrode leads are attached). Usually a reducing
polarising voltage (applied potential) of between –0.7 to –0.8 V isrequired at the working electrode to effect the reaction:+–

O 2 + 4H + 4e → 2H 2 O
The exact potential can be varied to suit the sample being measured
and to minimise side reactions. A smaller potential reduces sensitivity
but is usually more selective for oxygen.
Most oxygen sensors exhibit a slow response time and will take at least
several seconds to stabilise. Thus you would normally employ a1 – 10 Hz filter setting on the Potentiostat or Picostat in order tominimise any electrical noise. The Mains Filter setting can also be
employed to further reduce mains hum.
If you intend to monitor oxygen concentrations over a wide range then
you can calibrate the electrode at several concentrations and use theChart software Multiple Point Calibration extension to compensate for anon-–linear electrode response. You can download the extension fromwww.edaq.com.

Nitric Oxide (NO) Sensors
Most polarographic nitric oxide sensors can be used with the Picostat,which is suitable for detecting the small currents (<100 nA) expectedfrom the low concentrations of nitric oxide found in natural biologicalsystems.
Most commercial nitric oxide sensors comprise a carbon fibre anodic
working electrode (to which the working electrode lead is attached)
and a cathodic counter electrode (to which the reference and auxiliaryelectrode leads are attached). Usually an oxidising polarising voltage

60

Potentiostat & Picostat

(applied potential) of up to +1.0 V is required at the working electrode,to effect the reaction:–+

NO + 2H 2 O → NO3 + 4H + 3e–

The exact potential can be varied to suit the type of electrode (manyelectrodes have special catalytic surface coatings), the sample being
measured, and to minimise side reactions.
At potentials smaller than +0.7 V, the current signal is usuallydependent on the polarising voltage, but between +0.7 and +0.1 V thecurrent signal tends to plateau as the reaction is limited by the rate at
which nitric oxide can diffuse to the anode surface. At potentials
greater than +1.0 V the hydrolysis of water gradually becomes thedominant source of the current signal.
Most nitric oxide sensors exhibit a slow response time and will take atleast several seconds to stabilise. Thus you would normally employ a1 – 10 Hz filter setting with the Picostat in order to minimize any
electrical noise. The Mains Filter setting can also be employed to further
reduce mains hum.
It is recommended in most cases to calibrate the electrode at several
nitric oxide concentrations covering your range of interest. Use theChart software Multiple Point Calibration extension which can be
downloaded from the eDAQ web site at www.edaq.com.

Chapter 4 — Techniques

61

62

Potentiostat & Picostat

A

P

P

E

N

D

I

X

A

A Technical Aspects

This appendix describes the some of the technical aspects of the
Potentiostat — you do not need to understand the material here to use
the Potentiostat or Picostat. Please note that this information is notintended as a service manual and that user modification of theequipment voids your rights under warranty.
The Potentiostat, Picostat and other eDAQ Amps have been designed to
be used with a e-corder system. All internal functions (gain ranges,
filters, real/standby/dummy cell selection) of the Potentiostat or Picostat
are controlled from the e-corder by sending information on a special
communications connection called the ‘I2C bus’ which also supplies
power to the Potentiostat or Picostat.

Potentiostat
The Potentiostat is designed to function as either a potentiostat (Chart,
Scope or EChem software) or a galvanostat (Chart and Scope software
only). The mode of operation under software control. A block diagramof the Potentiostat circuitry is shown in Figure A–1.
The Potentiostat is also fitted with an internal 100 kΩ dummy cellshown in Figure A–2. The dummy cell is physically connected wheneverthe ‘Real cell’ mode is not being used.
The Potentiostat is powered by regulated +17 V, –17 V and +8 V DC
lines from the e-corder, see Figure 2–3 on page 9.

Potentiostat & Picostat

63

Figure A–1
Block diagram of the
Potentiostat.

Front PanelE Out

Working

Back Panel

E In

Auxiliary

Reference
ShieldOverload

Multiport Connector

DIN Connector

Shield
–
+

Dummy
Cell
+

+

+
–

Current
Range

–

–

LP Filter
Overload
detector

I Out

I2C Control
Interface

OnlineAuxiliary

Figure A–2
The Potentiostat 100 kΩ
Dummy Cell.

10 kΩ

10 nF

Reference
Working

100 kΩ

The Potentiostat has four gain ranges of 100 nA/V, 1 µA/V,
100 µA/V, and 10 mA/V. The maximum current output signal (I Out) is
10 V at any gain setting. Secondary amplification of the current signal
is done by the e-corder. The gain and secondary amplification are set
by the single ‘range’ menu in the software which offers a combined
total of 19 current range settings from ±20 nA to ±100 mA in 1:2:5
steps.
The Potentiostat uses a VCCS (Voltage Controlled Current Source)
design based on a Howland current pump. A differential input amplifiercompares the difference in potential between the reference electrodeand the excitation potential set on the analog output of the e-corder.
The output of this amplifier provides an error signal to the VCCS which
drives a current through the auxiliary electrode to try to zero the error
signal. By using a VCCS the working electrode of the cell can bedirectly connected to ground. This is a safe configuration particularly

64

Potentiostat & Picostat

suitable for student use. Further information on the basic design can beobtained from ‘A Potentiostat Based on a Voltage-Controlled Current
Source for use with Amperometric Gas Sensors’, J. C. Fidler, IEEE
Transactions on Instrumentation and Measurements, 41, 1992.
The high impedance reference and auxiliary electrode lead wires areactively shielded (that is, the shield is driven at the same potential as
the lead wire itself) to minimise electrical interference.

Picostat
The Picostat is designed to function in potentiostatic mode only, that is it
cannot be used as a galvanostat. A block diagram of its construction isshown in Figure A–3.
The Picostat is powered by regulated +17 V, –17 V and +8 V DC lines
from the e-corder, see Figure 3–3 on page 23.
An error voltage is generated from the difference between the voltage
on the Reference electrode and the excitation (command) voltage set by
the e-corder unit. This difference or error voltage drives a high gain
power amplifier (VCVS – voltage controlled voltage source) the output
of which is applied to the Auxiliary electrode in such a way as tominimise the error voltage.

Figure A–3
Block diagram of thePicostat.

Overload
Detector

Front Panel

Back Panel

Overload
OperatePower Amp

Auxiliary
Disconnect

Gain
Ref Amp

Error
Voltage+–

E In(Commandvoltage)

E Out(Reference
voltage)

Hi Z

Reference
ShieldSubtractor

OperateLow–pass Filter

I Out

Virtual Ground (0 V)
Working
ShieldOnlineAppendix A — Technical Aspects

I to VI2C Control
Interface

I2C Input
I2C Output

65

The Picostat, and the electrochemical cell to which it is connected,
forms a composite feedback control system in which the value of the
Auxiliary voltage is controlled in such a way as to make the Reference
voltage equal to the desired Command voltage. The current flow in the
Working electrode is the quantity being measured.
When the Picostat is in Standby mode the Working and Referenceelectrodes are disconnected by an internal relay. This prevents
unwanted current flowing through your electrochemical cell.
An overload condition is indicated when the error voltage exceeds asmall non-zero value. This indicates that the system could not establish
or sustain a balanced state. The Overload light will be reset when
scanning is stopped or when the Picostat controls are next accessed.
The reference voltage is measured by a high input impedance amplifier
which provides a low impedance output to the e-corder unit.
The voltage at the working electrode is effectively held at a virtual
ground potential (zero volts) by a voltage-to-current converter, theoutput of which reads directly in current units and is also applied to thee-corder unit. The Picostat has three gain ranges of 100 pA/V,
1 nA/V, and 10 nA/V. The maximum current output signal (I Out) is
10 V at any gain setting. Secondary amplification of the current signal
is done by the e-corder. The gain and secondary amplification are set
by the single ‘range’ menu in the software which offers a combined
total of eleven current range settings from ±10 pA to ±100 nA in 1:2:5
steps.
The coaxial shields of the reference and working electrode lead wires(which carry a high impedance signal) are maintained at the samepotential as the lead wire itself to minimise electrical interference, andreduce lead capacitance.

66

Potentiostat & Picostat

A

P

P

E

N

D

I

X

B Troubleshooting

B

This appendix describes some problems that may arise when using the
Potentiostat or Picostat. There is also help in your e-corder Manual and
Software Manuals, located on the eDAQ Software Installer CD.
In many cases, a problem can be fixed by turning the e-corder andcomputer off, checking connections, and starting again. Also try
performing the maintenance checks on page 18 and page 33. If you
cannot correct the problem, then please contact your eDAQ
representative.
The 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 Potentiostat or Picostat is properly connected to thee-corder and that the cables are not loose. Especially check that the‘E in, ‘I Out’ and ‘E Out’ cables are correctly connected, seepage 10, and page 25.
• 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 Potentiostat or
Picostat ‘E In’ cable is connected to the e-corder output and the ‘I
Out’ and ‘E Out’ cables are connected to Input Channels 1 and 2,
see page 10, and page 25.
• Try using the Potentiostat or Picostat with another e-corder (ifavailable). If the Online indicator fails to light on the second

Potentiostat & Picostat

67

e-corder, the Potentiostat or Picostat may be faulty — contact eDAQ.
If the Potentiostat or Picostat works correctly on a second e-corderthen the first e-corder may be faulty — contact eDAQ.
The ‘Potentiostat’ or ‘Picostat’ controls cannot be accessed in Chart,
Scope or EChem software (that is only the standard ‘Input Amplifier’dialog box of the e-corder can be accessed)• Check that the Potentiostat or Picostat Online indicator is on after
the software has been opened. If not, then proceed as in theprevious problem.
• Check that you have connected the ‘E In’, ‘I Out’ and ‘E Out’cables correctly to the appropriate e-corder connectors.
The Overload indicator is on (the Potentiostat or Picostat is experiencing
a potential overload).
• Check that the electrode cables are firmly attached to theelectrodes.
• Check that the surfaces of the electrodes have not become fouled.
• The Picostat Overload indicator may come on when the softwareis started — this is normal. The Overload indicator light should goout when you open the Picostat controls, or start recording.
• See Chapter 2 page 7, and Chapter 3 page 22 for more details.
The current signal goes off scale.
• Increase the full scale current range setting.
• Make sure each electrode is connected to the correct lead wire,
page 7 and page 21.
• Make sure the electrodes (and the alligator clips connecting themto the lead wires) are not touching 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.

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Potentiostat & Picostat

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 Potentiostat, page 9, or Connecting
the Picostat, page 25.
• 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(yellow) lead wire, page 7 and page 21. Connection of thereference electrode to either the working or auxiliary leads can also
cause rapid electrode deterioration 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 on page 16
and page 31.

Appendix B — Troubleshooting

69

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(yellow) lead wire!
• 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
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 the 10 Hz filter of the Potentiostat or Picostat torecord your results, see page 15 and page 31. Get an electrical
technician to check that the grounding of the power socket itself is ingood 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 alligator clips where
they are subject to mechanical wear. Use a multimeter to ensure thatthe clips are still in good electrical contact with the correct pins in

70

Potentiostat & Picostat

the input connector of the electrode cable, see Figure 2–2 onpage 6, and Figure 3–3 on page 23. Also check that the shield pins
have not shorted to any of the alligator clips.
• 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 (and even the
Potentiostat or Picostat) should be enclosed by a Faraday cage. A
Faraday cage (or other electrical shielding) is almost always
required when measure small currents with the Picostat.
• 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
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 B — Troubleshooting

71

72

Potentiostat & Picostat

A

P

P

E

N

D

I

C Specifications

X

C

Potentiostat
Electrometer & Power Amp
Potentiostat type:
Compliance voltage:

Voltage Controlled Current Source.
Galvanostat mode available.
> 10 V

Output current:±100 mA maximum

Input resistance:

1013 Ω

Input bias current:< 10 pA @ 25˚C

Current Measurement and Control
Current range settings:

Gain:
Maximum current signal:
Low pass filters:

Potentiostat & Picostat±100, 50, 20, 10, 5, 2, 1 mA
±500, 100, 50, 20, 10, 5, 2, 1 µA
±500, 100, 50, 20 nA
10000, 100, 1, 0.1 µA/V
10 V
10000, 1000* Hz, 4th order Bessel
100*, 10* Hz, 2nd order Bessel* These settings are used alone with
Scope and EChem software and with thecorresponding e–corder digital filters with
Chart software.

73

Slew rate:
Drift with temperature:

3 V/µs< 10 µV/˚C

Control Port
Multiport/I2C:

Power requirements:

Centronics 24 pin. Provides control andpower to the Potentiostat along withanalog signal connections to the e-corder.
±17 V DC
+8 V DC
25 mA typical
2W

Physical Configuration
Dimensions (h × w × d):
Weight:Operating conditions:

50 × 76 × 260 mm
1.96 × 3.0 × 10.2 inches
0.8 kg (1.8 lb)
0 – 35˚C
0 – 90% humidity (non-condensing)eDAQ reserves the right to alter these specifications at any time.

74

Potentiostat & Picostat

Picostat
Electrometer & Power Amp
Compliance voltage:> 13 V

Maximum control voltage:±10 V

Output current:±100 nA maximum

Input impedance:

1013 Ω || 1 pF

Input bias current:< 250 fA @ 25˚C (60 fA typical)

Current Measurement and Control
Current ranges:
Gain:
DC current error:
Filter setting:

Filter type:±100, 50, 20, 10, 5, 2, 1 nA
±500, 50, 20, 10 pA
10, 1, 0.1 nA/V
< ±1% FS on ranges of 10 pA – 1 nA
< ±0.5% FS on ranges of 2 – 100 nA
10 Hz low-pass. Used alone with Scopeand EChem software, and with thecorresponding e-corder setting with Chart
software.
3rd order Bessel

Bandwidth, unfiltered:> 10 kHz, on ranges of 20 – 100 nA~ 1 kHz, on ranges of 10 pA – 10 nA

Drift with temperature:< 20 µV/˚C

Control Port

Appendix C — Specifications

I2C input and output:

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

Power requirements:±17 V DC, ~ 20 mA+8 V DC, ~ 20 mA~ 1 W quiescent75

Physical Configuration
Dimensions (h × w × d):
Weight:Operating conditions:

50 × 76 × 260 mm
1.96 × 3.0 × 10.2 inches
0.8 kg (1.8 lb)
0 – 35˚C
0 – 90% humidity (non-condensing)eDAQ reserves the right to alter these specifications at any time.

76

Potentiostat & Picostat

A

P

P

E

N

D

I

X

D Electrochemical
EquationsD

Linear Sweep and Cyclic
Voltammetry
The Randles-Sevcik Equation
For a substrate with a reversible redox reaction, at a planar disk
electrode, in an unstirred solution, the peak current during linear
sweep, or cyclic voltammetry, is given by the Randles–Sevcik equation:i p = 269n3⁄2ai p = – 269 n

AD

3⁄2

c

1⁄2

AD

Cν

1⁄2

1⁄2

for an oxidation (anodic scan)

1⁄2

for a reduction (cathodic scan)CνThe potential where this occurs is given by:
E p = E 1⁄c20.0285– -----------------------------n

E p = E 1⁄a2

0.0285+ -----------------------------n

where
ip

a

= current peak during anodic scan (A)i p = current peak during cathodic scan (A)cE p = potential at current peak for anodic scan (V)aE p = potential at current peak for cathodic scan (V)c= half potential as determined by cyclic voltammetry (V)2n = the number of electrons transferred to (or from) the substratemolecule
A = area of the exposed surface of the electrode (cm2)

E 1⁄

Potentiostat & Picostat77D = diffusion coefficient of the substrate molecule (cm2/s)
C = concentration of the substrate molecule (mol/L)ν = the scan rate (V/s).
The factor of 269 is a parameter that derives from using a planarelectrode at a temperature of 298 K.
Thus a truly reversible reaction can be identified by examining theadherence of the system to the following functions:
ip ∝ ν

Ep independence of the scan rate, υIn addition cyclic voltammograms will exhibit:
Ep – Epacip------aip= 1

57= -----nmV (at 298 K)c

When working in highly resistive solutions, which is often the casewhen using organic solvents for cyclic voltammetry, the referenceelectrode should be kept as close as possible to the working electrodeto minimise iR drop. Nonetheless there may still be an appreciable
uncompensated resistance which will cause E pa – E pc to become larger
than predicted, the peaks to be broader, and the peak currents to besmaller.

78

Potentiostat & PicostatChronoamperometry
The Cottrell Equation
When chronoamperometry is performed on an unstirred solution at aplanar electrode the faradaic current response is described by the
Cottrell equation
1⁄

nFAD 2 C
i = ---------------------------------1⁄ 1⁄1000π 2 t 2
where
n = the number of electrons transferred to (or from) the substratemolecule
F = Faraday's constant, 96485 C/mol
A = area of the exposed surface of the electrode (cm2)
D = diffusion coefficient of the substrate molecule (cm2/s).
C = concentration of the substrate molecule (mol/L)t = time (s).
The factor of 1000 is to bring both cm and dm (1 dm3 = 1000 cm3 =1 L ) in the equation to common units.
Thus a plot of i versus 1/√t should produce a straight line.
In aqueous solution the coefficient of diffusion usually has a value of
between 10–5 and 10–6 cm2/s.

Appendix D – Electrochemical Equations

79

Chronocoulometry
The Integrated Cottrell Equation
The current response equation at a planar electrode for achronocoulometric experiment is the time integrated form of the Cottrell
equation:
Q =

t

1⁄

1⁄

2nFAD 2 Ct 2-+ki dt = ---------------------------------------1⁄01000π 2∫where
Q = the number coulombs transferredn = the number of electrons transferred to (or from) the substratemolecule
A = area of the exposed surface of the electrode (cm2)
D = diffusion coefficient of the substrate molecule (cm2/s).
C = concentration of the substrate molecule (mol/L)t = time (s)k = a constant.
Thus a plot of Q versus t1/2 should produce a straight line with anintercept of k, which in turn can be defined as:
k = nFAΓ + Qdl
whereΓ = surface concentration of adsorbed substrate (mol/cm2)
Qdl = double layer charging.

80

Potentiostat & Picostat

Overload

Picostat

Index

A
amperometric sensors 58
amperometry 35, 56

Bback panel
Picostat 23
Potentiostat 8
biosensors 59

curve fitting 44
cyclic voltammetry 35, 37, 77Ddifferential pulse voltammetry 35
dissolved oxygen sensor 59

E

Bridge Amp 2

E In connector
Picostat 23

C

E Out connector
Picostat 23

calibration
multiple point 58
non–linear 58
two point linear 58
checking procedure 3
chronoamperometry 39, 79
analysis 43
Chart
Macintosh 40
Windows computers 39
multiple step 41, 44, 48
Scope 48
chronocoulometry 49, 80
chronopotentiometry 51
compliance 58
Cottrell equation 43, 49, 79
integrated form 80

Potentiostat & Picostat

EChem software 1, 35
eDAQ Amps 2
Bridge Amp 2
GP Amp 2
pH Amp 2
Picostat 2
Potentiostat 2
electrochemical equations 77
electrode cable
Picostat 21
Potentiostat 7
electrode leads
color-coding
Picostat 21
Potentiostat 7
shielding
Picostat 21
Potentiostat 781

electrolysis
controlled current 57
controlled potential 56
electropolymerisation 56, 58

linear sweep voltammetry 35, 77

Melectrosynthesis 56, 57, 58

Mains Filter 70

FmaintenancePicostat 33
Potentiostat 18

Faraday cage grounding cable 24

mains hum 70

Faraday's constant 79

microdialysis sensor 59

fast cyclic voltammetry 36, 37

multiple step chronoamperometry 41, 44, 48

fast linear sweep voltammetry 36

Multiport cable
Potentiostat 9

front panel
Picostat 20
Potentiostat 6

Multiport connector
Potentiostat 8

GN

galvanostat 14, 36
setting current values 51

nitric oxide sensor 60

galvanostat mode 51

normal pulse voltammetry 35

noise 24, 70

GP Amp 2
ground loop 25
grounding cable 24
grounding connector
Picostat 24

I

O
Ohm’s law 18, 29
Online indicator
Picostat 21
Potentiostat 7

I Out connector
Picostat 23

Overload indicator
Picostat 22
Potentiostat 7

I2C connector
Picostat 23

P

input amplifier 11, 27

pH Amp 2

input connector
Picostat 20
pin assignments 20
Potentiostat 6
pin assignments 6

Picostat 2

integrated Cottrell equation 80

Llead wire capacitance 20
linear scan techniques 36

82

polarity
Picostat 26
Potentiostat 10
polyaniline 56
polypyrrole 56
potential overload 58
Potentiostat 2
problems 67
pulsed amperometry 35
Potentiostat & Picostat

R
Randles-Sevcik equation 77
reference electrodeaging and regeneration 70

Ssensorsamperometric 58
biosensors 59
dissolved oxygen 59
microdialysis 59
nitric oxide 60
specifications
Picostat 75
Potentiostat 73
square wave voltammetry 35
static discharge 19, 33

T
Timed Events 42, 56
two-electrode operation
Picostat 21
Potentiostat 7

Vvoltammetry
cyclic 35, 77differential pulse 35
fast cyclic 36, 37
fast linear sweep 36
linear sweep 35, 77
normal pulse 35
square wave 35

Index

83

84

Potentiostat & Picostat

OverloadPotentiostat

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 the Potentiostat or Picostat, tobe free of 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 we

Potentiostat & Picostat

will issue you with a RAN (return authorization
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 the 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

85

copies of a program may exist on several
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 or Picostat.
• 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.

86

Potentiostat & Picostat