Reference 3000 Potentiostat Operator`s Manual

Reference 3000 Potentiostat Operator`s Manual
Reference 3000™
Potentiostat/Galvanostat/ZRA
Operator’s Manual
Copyright © 2012–2015 Gamry Instruments, Inc.
Revision 6.1
December 2, 2015
988-00014
If You Have Problems
Please visit our service and support page at www.gamry.com/service-support/. This page contains information
on installation, software updates, and training. It also contains links to the latest available documentation. If
you are unable to locate the information you need from our website, you can contact us via email using the link
provided on our website. Alternatively, you can contact us one of the following ways:
Internet
www.gamry.com/service-support/
Telephone
(215) 682-9330 9:00 AM - 5:00 PM US Eastern Standard Time
(877) 367-4267 Toll Free US & Canada Only
Please have your instrument model and serial numbers available, as well as any applicable software and
firmware revisions.
If you have problems in installation or use of a system containing a Reference 3000, it would be helpful if you
called from a phone next to your computer, where you can type and read the screen while talking to us.
We will be happy to provide a reasonable level of free support for registered users of the Reference 3000
Potentiostat/Galvanostat/ZRA. Reasonable support includes telephone assistance covering the normal
installation, use and simple customization of a computerized system containing a Reference 3000 connected to
a Windows compatible computer.
A service contract that extends both the hardware warranty and software update period is available at an
additional charge. Software updates do not include software enhancements offered to our customers at
additional cost.
Enhancements to the Reference 3000 and Gamry’s standard applications software that require significant
engineering time on our part can be performed on a contract basis. Contact us with your requirements.
i
Limited Warranty
Gamry Instruments, Inc. warrants to the original user of this product that it shall be free of defects resulting from
faulty manufacture of the product or its components for a period of two years from the original shipment date
of your purchase.
Gamry Instruments, Inc. makes no warranties regarding either the satisfactory performance of the Reference
3000 Potentiostat/Galvanostat/ZRA including the software provided with this product or the fitness of the
product for any particular purpose. The remedy for breach of this Limited Warranty shall be limited solely to
repair or replacement, as determined by Gamry Instruments, Inc., and shall not include other damages.
Gamry Instruments, Inc. reserves the right to make revisions to the system at any time without incurring any
obligation to install same on systems previously purchased. All system specifications are subject to change
without notice.
There are no warranties which extend beyond the description herein. This warranty is in lieu of, and
excludes any and all other warranties or representations, expressed, implied or statutory, including
merchantability and fitness, as well as any and all other obligations or liabilities of Gamry Instruments,
Inc; including but not limited to, special or consequential damages.
This Limited Warranty gives you specific legal rights and you may have others, which vary from state to state.
Some states do not allow for the exclusion of incidental or consequential damages.
No person, firm or corporation is authorized to assume for Gamry Instruments, Inc., any additional obligation or
liability not expressly provided herein except in writing duly executed by an officer of Gamry Instruments, Inc.
ii
Disclaimers
Gamry Instruments, Inc. cannot guarantee that the Reference 3000 Potentiostat/Galvanostat/ZRA will work with
all computer systems, operating systems, and third party software applications hardware/software.
The information in this manual has been carefully checked and is believed to be accurate as of the time of
printing. However, Gamry Instruments, Inc. assumes no responsibility for errors that might appear.
Copyrights
Reference 3000 Potentiostat/Galvanostat/ZRA Operator's Manual copyright 2008-2012, Gamry Instruments, Inc., all rights reserved.
Gamry Framework - copyright 1989-2012, Gamry Instruments, Inc., all rights reserved.
Reference 3000, Reference 600, Interface 1000™, PC4, PCI4, ECM8, Series G, Gamry
Framework, DC105, EIS300, and Gamry are trademarks of Gamry Instruments, Inc.
No part of this document may be copied or reproduced in any form without the prior written consent of Gamry
Instruments, Inc.
iii
--
Table of Contents
If You Have Problems .................................................................................................................... i
Limited Warranty .......................................................................................................................... ii
Disclaimers.................................................................................................................................... iii
Copyrights ..................................................................................................................................... iii
Chapter 1 -- Safety Considerations ................................................................................................. 1-1
Inspection ........................................................................................................................ 1-1
Product Safety .................................................................................................................. 1-1
AC Mains Connection to the Power Brick.......................................................................... 1-2
Grounding in the Reference 3000..................................................................................... 1-2
Operation with Earth Grounded Cells and Auxiliary Apparatus .......................................... 1-3
Temperature and Ventilation ............................................................................................ 1-3
Defects and Abnormal Stresses ......................................................................................... 1-4
Environmental Limits ........................................................................................................ 1-4
Cleaning........................................................................................................................... 1-5
Service ............................................................................................................................. 1-5
RFI Warning ..................................................................................................................... 1-5
Electrical Transient Sensitivity............................................................................................ 1-5
CE Compliance................................................................................................................. 1-6
RoHS Compliance ............................................................................................................ 1-6
Chapter 2 -- Introduction............................................................................................................... 2-1
About this Manual ............................................................................................................ 2-1
About the Reference 3000................................................................................................ 2-1
About the Auxiliary Electrometer Option........................................................................... 2-2
Notational Conventions .................................................................................................... 2-2
Chapter 3 -- Instrument Circuitry ................................................................................................... 3-1
Reference 3000 Schematic/Block Diagrams....................................................................... 3-1
Chapter 4 -- Installation ................................................................................................................. 4-1
Initial Visual Inspection ..................................................................................................... 4-2
Physical Location .............................................................................................................. 4-2
Computer Requirements................................................................................................... 4-3
Quick Start Guide for System Installation .......................................................................... 4-3
Software Installation.......................................................................................................... 4-3
Reboot your Computer after Software Installation.............................................................. 4-3
Power Cord and Power Connection .................................................................................. 4-4
Power Up Test.................................................................................................................. 4-5
USB Cabling ..................................................................................................................... 4-5
Front Panel USB LED........................................................................................................ 4-5
1st Time Device Installation in Windows XP....................................................................... 4-6
Running the Framework.................................................................................................... 4-8
Framework Device Status Bar ........................................................................................... 4-9
Gamry Instrument Manager .............................................................................................. 4-10
Authorization Codes and Label ......................................................................................... 4-11
Firmware Update ............................................................................................................. 4-13
Calibration ....................................................................................................................... 4-15
Separate Calibration for Each Reference 3000 Cable Type.................................... 4-15
DC and AC Calibration ........................................................................................ 4-15
Low I Range DC Calibration................................................................................. 4-16
Chapter 5 -- Cell Connections........................................................................................................ 5-1
Cell Cable Overview......................................................................................................... 5-1
--
Ancillary Apparatus.............................................................................................. 5-1
AE Connections ................................................................................................... 5-1
Fuses in the Cell Cable...................................................................................................... 5-1
Normal Cell Connections .................................................................................................. 5-1
ZRA Mode Cell Connections............................................................................................. 5-3
Stack Mode Cell Connections ........................................................................................... 5-4
Membrane Cell Connections............................................................................................. 5-5
Fuses in the Cell Cable...................................................................................................... 5-5
In-line Fuse-Holders and Fuses ............................................................................ 5-5
Fuses Located in the Cable Hood......................................................................... 5-6
Testing For Open Fuses ....................................................................................... 5-8
Chapter 6 -- Panel Indicators and Connectors................................................................................. 6-1
Front Panel....................................................................................................................... 6-1
Counter/Working Connector................................................................................ 6-1
Sense Inputs Connector ....................................................................................... 6-1
The Power LED ................................................................................................... 6-1
The USB LED ...................................................................................................... 6-2
Cell LED.............................................................................................................. 6-2
Overload LED...................................................................................................... 6-3
Rear Panel........................................................................................................................ 6-3
Power In Jack ...................................................................................................... 6-3
Power Switch ...................................................................................................... 6-4
Chassis Ground ................................................................................................... 6-4
USB Port ............................................................................................................. 6-4
Thermocouple Input............................................................................................ 6-5
Misc I/O Connector ............................................................................................. 6-5
I Monitor BNC..................................................................................................... 6-6
E Monitor BNC.................................................................................................... 6-6
Ext. Sig. In BNC ................................................................................................... 6-7
Sig Gen Out BNC ................................................................................................ 6-7
Aux In BNC ......................................................................................................... 6-7
Expansion Interface ............................................................................................. 6-8
Chapter 7 -- Auxiliary Electrometer Option .................................................................................... 7-1
Overview ......................................................................................................................... 7-1
AC Performance and CMRR.............................................................................................. 7-1
Experiments ..................................................................................................................... 7-2
Connections Using Standard Cables .................................................................................. 7-2
Connections Using Custom Cables .................................................................................... 7-3
AE Specifications .............................................................................................................. 7-3
Chapter 8 -- Stability in Potentiostat Mode ..................................................................................... 8-1
Capacitive Cells and Stability ............................................................................................ 8-1
Improving Potentiostat Stability ......................................................................................... 8-2
Chapter 9 -- Measurement of Small Current Signals........................................................................ 9-1
Overview ......................................................................................................................... 9-1
Problem Description......................................................................................................... 9-1
Measurement System Model and Physical Limitations ....................................................... 9-1
Johnson Noise in Zcell ......................................................................................... 9-3
Finite Input Capacitance ...................................................................................... 9-4
Leakage Currents and Input Impedance ............................................................... 9-4
Voltage Noise and DC Measurements .................................................................. 9-5
Shunt Resistance and Capacitance ....................................................................... 9-5
Hints for System and Cell Design ...................................................................................... 9-6
--
Faraday Shield..................................................................................................... 9-6
Avoid External Noise Sources............................................................................... 9-6
Cell Cable Length and Construction ..................................................................... 9-6
Lead Placement................................................................................................... 9-7
Cell Construction................................................................................................. 9-7
Reference Electrode............................................................................................. 9-7
Instrument Settings .............................................................................................. 9-8
EIS Speed ............................................................................................................ 9-8
Ancillary Apparatus.............................................................................................. 9-8
Floating Operation............................................................................................................ 9-8
Chapter 10 – EIS Measurement of Small Impedances ..................................................................... 10-1
Overview ......................................................................................................................... 10-1
Why Galvanostatic Mode? ................................................................................................ 10-1
DC Errors and Four-terminal Measurements ...................................................................... 10-2
What is Mutual Inductance? ............................................................................................. 10-3
Avoid high frequencies ........................................................................................ 10-3
Minimize the Net Magnetic Field ......................................................................... 10-3
Separate the pairs ................................................................................................ 10-4
Twist the Sense Wires.......................................................................................... 10-4
How Should You Hook Up Your Cell?............................................................................... 10-4
Appendix A -- Reference 3000 Specifications ................................................................................. 11-1
Appendix B -- Reference 3000 Cell Connectors.............................................................................. 12-1
Appendix C -- Misc I/O Connector................................................................................................. 13-1
Appendix D -- Auxiliary A/D Input Characteristics .......................................................................... 14-1
Overview ......................................................................................................................... 14-1
Jumper Identification ........................................................................................................ 14-1
Input Impedance Selection ............................................................................................... 14-2
Bandwidth Selection......................................................................................................... 14-3
Aux A/D Specifications ..................................................................................................... 14-3
Function Call to Set the Aux A/D BNC Characteristics........................................................ 14-3
Appendix E – Auxiliary Electrometer Specifications ......................................................................... 15-1
DC Voltage Measurement................................................................................................. 15-1
Input Impedance .............................................................................................................. 15-1
Common Mode Rejection................................................................................................. 15-1
Crosstalk........................................................................................................................... 15-1
Other AC Specifications.................................................................................................... 15-2
Appendix F – CE Certificate ........................................................................................................... 16-1
Declaration of Conformity ................................................................................................ 16-1
Certificate of Conformance ............................................................................................... 16-2
Comprehensive Index.................................................................................................................... 17-1
Chapter 1 -- Safety Considerations--Inspection
Chapter 1 -- Safety Considerations
Your Reference 3000 Potentiostat/Galvanostat/ZRA has been supplied in a safe condition. This chapter of the
Reference 3000 Operator's Manual contains some information and warnings that you must follow to insure
continued safe operation of the Reference 3000.
The safety information in this chapter applies to both the Reference 3000 and the Reference 3000 equipped
with its AE Auxiliary Electrometer.
Inspection
When you receive your Reference 3000 Potentiostat/Galvanostat/ZRA you should inspect it for evidence of
shipping damage. If any damage is noted, please notify Gamry Instruments Inc. and the shipping carrier
immediately. Save the shipping container for possible inspection by the carrier.
WARNING
A Reference 3000 that has been damaged in shipment can be a safety hazard. Do not
operate damaged apparatus until a qualified service technician has verified its safety.
Tag a damaged Reference 3000 to indicate that it could be a safety hazard.
Product Safety
The Reference 3000 has been designed, tested and certified to meet the requirements of an international
standard, EN 61010, Safety requirements for electrical equipment for measurement, control, and laboratory
use. As defined in this standard, it is a Category II apparatus, with any "hazardous live voltages" protected by
"reinforced insulation".
The Reference 3000 contains a limited amount of internal circuitry that operate at “hazardous live” voltages as
defined in EN 61010 (the standard mentioned above). “Reinforced insulation” (again defined in EN 61010) is
used to reduce the risk of electrical shock due to this “hazardous live” voltage.
The majority of the Reference 3000’s circuitry does not contain voltages higher than 42 Volts DC. As a
generalization, input and output voltages in the Reference 3000 are limited to 36 volts. This voltage level is
considered safe.
The “AC Adapter” supplied with the Reference 3000 is certified under EN 60950. The AC Adapter converts
the AC mains voltage to 24 volts DC, which is used to power the Reference 3000.
You should always use the AC adapter (power brick) supplied with your Reference 3000 to supply DC power to
the instrument.
WARNING
Do not use a DC power source other than the AC adapter model provided with your
Reference 3000. Other replacements may void the performance and/or safety
characteristics of the Reference 3000.
1-1
Chapter 1 -- Safety Considerations--AC Mains Connection to the Power Brick
AC Mains Connection to the Power Brick
The Reference 3000 does not connect directly to an AC Mains supply. Instead, the mains are connected to
desktop AC adapter (power brick), which outputs 24 volts DC, which in turn powers the Reference 3000.
NOTE
The Reference 3000’s AC Adapter is rated for operation from 100 to 240 volts AC, 47 to
63 Hz. It should therefore be useful throughout the world.
The Reference 3000 is normally provided with an AC line cord suitable for your location. This AC line cord
connects the AC mains to the AC power adapter. If your Reference 3000 has been provided without an AC
line cord, or a cord that is not compatible with your local AC mains socket, obtain a line cord certified for use in
your country. Contact your local Gamry Representative or Email to [email protected] if you are
uncertain what AC line cord to use.
Grounding in the Reference 3000
The circuitry and the metal case of the Reference 3000 are not connected to an earth ground. If they were
connected to earth ground, it would compromise the Reference 3000’s ability to make measurements in
electrochemical cells that contain earth grounded conductors. A few examples of such cells include autoclaves,
metallographic stress apparatus, chemical storage tanks, and most large fuel cell stacks.
Most electrochemical cells are isolated from earth ground, so isolation of the Reference 3000 from earth is not
required. In these cases, connection of the Reference 3000 chassis to an earth ground may lower noise seen in
electrochemical tests. A Chassis Ground binding post on the rear panel of the Reference 3000 makes for easy
implementation of this connection. Simply run a wire from this binding post to a suitable source of earth
ground. A black 1.2-meter wire is provided with the Reference 3000 to facilitate this connection.
NOTE
Sources of earth ground include;
•
•
•
Most metal water pipes,
the chassis of most electronic apparatus (which are generally earth grounded), and
the protective ground terminal of an AC Mains power plug.
We recommend that you discuss grounding with an electrical or electronics professional
prior to making this earth ground connection.
Note this connection of the Reference 3000 to an earth ground is not a “Protective Earth Ground” as defined in
EN 61010. The Reference 3000 is safe in the absence of this connection.
This binding post is not intended for any use other than connecting the Reference 3000 to an earth ground to
improve shielding against noise. Connecting this binding post to a hazardous voltage can create a significant
safety hazard.
WARNING
Do not connect the chassis ground binding post to any voltage other than earth
ground. An improper connection can create a safety hazard, which could result in
personal injury or death.
1-2
Chapter 1 -- Safety Considerations--Operation with Earth Grounded Cells and Auxiliary Apparatus
An earth ground connection can cause problems when testing batteries, fuel cells, or capacitors. Many of these
devices can source huge currents, often 10’s or 100’s of amps. If the Reference 3000 chassis is earth grounded
and another location in the stack is accidentally (or intentionally) connected to earth ground, a portion of the
stack is shorted through the Reference 3000’s cell cable. Very large current flows when this occurs. Fuses in
the cell cable will open up to prevent damage to the instrument. When this happens, the failed fuses must be
replaced before the instrument can be used again. The fuses in the cell cable are not essential for operator
safety. A section in Chapter 5 describes the fuses and their replacement in detail.
NOTE
The fuses in the Reference 3000 cell cable do not protect against a safety hazard. They
are needed to prevent damage to the instrument if it is improperly connected.
Operation with Earth Grounded Cells and Auxiliary Apparatus
As described above, the Reference 3000 circuitry is isolated from earth ground, allowing it to make
measurements on cells that include an earth ground. This ground isolation is often called floating operation.
Cells with earth ground include many autoclaves, pipelines and storage tanks, and many fuel cell systems.
Connection of the Reference 3000 to auxiliary apparatus will often earth ground the Reference 3000,
destroying its ability to float and make measurements on earth grounded cells. Connection of the Monitor
BNCs to an oscilloscope is an example where the instrument is earthed.
The User I/O connector can be connected to earth grounded apparatus without earth grounding the Reference
3000, if the cabling is done carefully. The Metal Shell on the Reference 3000 User I/O Connector is
connected to the instrument's chassis which is a Floating ground. In a system that needs isolation from earth
ground, the shield of a User I/O cable must not connect the D-connector's metal shell to earth ground. All
User I/O signals should be referenced to pin 6 of the D-connector, which is isolated ground on the Reference
3000.
Caution
Floating operation of the Reference 3000 can be compromised by improper cabling to the
User I/O Connector. Do not use standard 15-pin shielded cables with this connector.
Custom cables with the shield connected to pin 6 of the D-connector are required.
WARNING
Do not connect the chassis ground binding post to any voltage other than earth ground.
An improper connection can create a safety hazard, which could result in personal injury
or death.
The Reference 3000 contains surge suppressors that limit the voltage difference between the Reference 3000’s
chassis ground and earth ground to about 40 volts. These surge suppressors are not part of the safety
mechanisms in the Reference 3000. Instead they are present to limit the possibility of improper instrument
operation or instrument damage due to electrostatic discharge (static electricity) and other surge events such as
lightening.
Temperature and Ventilation
Your Reference 3000 Potentiostat/Galvanostat/ZRA was designed for indoor use at ambient temperatures
between 0°C and 45°C.
1-3
Chapter 1 -- Safety Considerations--Defects and Abnormal Stresses
The Reference 3000 uses forced air-cooling to keep its electronic components within their recommended
operating temperature range. Three fans on the rear panel of the Reference 3000 draw air into the chassis.
The air exits from slots located on the sides of the chassis near the front panel.
CAUTION
Do not block the airflow into or out of the Reference 3000 chassis. While the circuitry
should shut down before it is damaged from excessive heat, the Reference 3000
enclosure may become uncomfortably hot to the touch if insufficient air flows through
the chassis. Running the Reference 3000 without adequate cooling could shorten the
time to failure of some of the circuitry.
Be careful when operating the Reference 3000 in an enclosed space (such as an enclosed relay rack or NEMA
enclosure). The temperature within the enclosure must not exceed 45°C. You may need to provide ventilation
holes or even forced air-cooling for the enclosed space if you determine that there is an excessive temperature
rise within the space.
Defects and Abnormal Stresses
You should treat your Reference 3000 as potentially hazardous if any of the following is true of the unit:
•
•
•
•
•
it shows visible damage,
it does not operate properly,
it has been stored for a long period of time under unfavorable conditions,
it has been dropped or subjected to severe transport stress,
it has been subjected to environmental stress (corrosive atmosphere, fire, etc.).
Do not use your Reference 3000 or any other apparatus if you think it could be hazardous. Have it checked by
qualified service personnel.
Environmental Limits
Note that there are environmental limit conditions on the storage, shipping and operation of this equipment.
The Reference 3000 has not been designed for outdoor use.
Storage
Shipping
Ambient Temperature
Relative Humidity
-40 °C to 75 °C
Maximum 90% non-condensing
Same as storage plus
Acceleration
Maximum 30 G
Ambient Temperature
Relative Humidity
0 °C to 45 °C
Maximum 90% non-condensing
Operation
1-4
Chapter 1 -- Safety Considerations--Cleaning
WARNING
The Reference 3000 is not designed for operation in conditions where liquid water
may enter the chassis, or water vapor may condense within the chassis. Operation of
a Reference 3000 that has water within the chassis can create a safety hazard, which in
extreme cases could result in personal injury.
Cleaning
Disconnect the Reference 3000 from all power sources prior to cleaning.
Use a cloth lightly dampened with either clean water or water containing a mild detergent to clean the outside
of the Reference 3000 enclosure. Alternatively, you can use isopropyl alcohol. Do not use a wet rag or allow
fluid to enter the Reference 3000 enclosure. Do not immerse the Reference 3000 in any type of cleaning fluid
(including water). Do not use any abrasive cleaners.
Service
Your Reference 3000 Potentiostat/Galvanostat/ZRA has no user serviceable parts inside. You should refer all
service to a qualified service technician.
WARNING
The Reference 3000 must not be operated with any cover or panel on the chassis
open. Dangerous voltages may present at several points within the Reference 3000
chassis, including PC board traces. Always remove the power connection before
opening the Reference 3000 case.
RFI Warning
Your Reference 3000 Potentiostat/Galvanostat/ZRA generates, uses, and can radiate radio frequency energy.
The radiated levels are low enough that the Reference 3000 should not create an interference problem in most
industrial laboratory environments.
The Reference 3000 has been tested for both radiated and conducted RF interference and has been found to
be in compliance with FCC Part 18 and EN 61326:1998—Electrical equipment for measurement, control, and
laboratory use— EMC Requirements.
Electrical Transient Sensitivity
Your Reference 3000 Potentiostat/Galvanostat/ZRA was designed to offer reasonable immunity from electrical
transients, including transients on the incoming AC Mains supply and Electrostatic Discharge. It has been
tested for compliance with EN 61326:1998—Electrical equipment for measurement, control, and laboratory
use— EMC Requirements describing acceptable limits for Electrical Transient susceptibility in Laboratory Test
equipment. The Reference 3000 is not rated for continuous use when subject to ESD events. It should suffer
no permanent damage when subject to the standard ESD events defined in EN61326, but may cease normal
operation until it is powered down and restarted.
In severe cases, the Reference 3000 could malfunction as a result of electrical transients such as a static
discharge. If you are having problems in this regard, the following steps may help:
If the problem is static electricity (sparks are apparent when you touch the Reference 3000 or its cables):
•
Placing your Reference 3000 on a static control work surface may help. Static control work surfaces
are now generally available from computer supply houses and electronics tool suppliers. An antistatic
floor mat may also help, particularly if a carpet is involved in generating the static electricity.
•
Air ionizers or even simple air humidifiers can reduce the voltage available in static discharges.
1-5
Chapter 1 -- Safety Considerations--CE Compliance
If the problem is AC power line transients (often from large electrical motors near the Reference 3000):
•
Try plugging your Reference 3000 into a different AC power branch circuit.
•
Plug your Reference into a power line surge suppressor. Inexpensive surge suppressors designed for
use with computer equipment are now generally available.
Contact Gamry Instruments, Inc. if these measures do not solve the problem.
CE Compliance
The European Community has instituted standards limiting radio frequency interference emitted by electronic
devices, setting limits for susceptibility of apparatus to RF energy and transient events, and mandating safety
requirements. Gamry Instruments, Inc. has designed and tested the Reference 3000 to comply with these
standards.
The relevant CE regulations include EN 61010 and EN 61326.
RoHS Compliance
The Reference 3000 has been built using lead free components and lead free solder. It is in compliance with
the European RoHS initiative.
1-6
Chapter 2 -- Introduction--About this Manual
Chapter 2 -- Introduction
About this Manual
This manual covers the installation, safety, and use of the Gamry Instruments Reference 3000
Potentiostat/Galvanostat/ZRA. It also includes information about the Reference 3000’s AE Auxiliary
Electrometer option.
This manual describes use of a Reference 3000 with Revision 6.00 (and later revisions) of the Gamry
Framework software. It is equally useful when setting up a newly purchased potentiostat or modifying the setup
of an older potentiostat for use with new software.
Chapter 1 was an in-depth discussion of safety issues. This chapter describes this manual and gives a brief
overview of the Reference 3000 features. Chapter 3 is a description of the electronics circuitry in the Reference
3000. Chapter 4 contains Reference 3000 installation instructions. Chapter 5 describes cell cable connections
and Chapter 6 describes the Reference 3000’s Front and Rear Panels. Chapter 7 discusses the AE Auxiliary
Electrometer option. Chapter 8 covers the difficult issues of potentiostat stability and approaches to prevent
oscillation. Chapter 9 discusses the realities of low current, high impedance measurements while Chapter 10
does the same for low impedance EIS.
You will find dry technical material such as specifications and connector pin-outs in the Appendices.
This manual does not discuss software installation or software operation in any detail.
Software support for the Reference 3000 is described in the Gamry Framework’s Help system.
All the Gamry Instruments' applications running under the Gamry Framework, control the Reference 3000 via a
PSTAT object. See the Framework’s Help system for information concerning PSTAT objects and their functions.
About the Reference 3000
The Reference 3000 Potentiostat is a research grade electrochemical instrument packaged in a small, easy to
handle case. It is the larger, higher current brother of Gamry’s extremely popular Reference 600 Potentiostat.
It is especially useful when currents higher than the 600 mA current limit of the Reference 600 are required.
Typical applications for the Reference 3000 include research regarding batteries, fuel cells and super-capacitors.
It should also prove useful in studies involving electrochemical synthesis, electroplating and corrosion. While it
can apply and measure ampere level currents, it is also an excellent small signal potentiostat that can work with
picoamp and sometimes even femtoamp current levels.
The Reference 3000 offers measurement capabilities similar to instruments many times larger in size, weight
and price. The Reference 3000 can operate as a potentiostat, a galvanostat, or a ZRA (zero resistance
ammeter). A new stack mode allows precision control and/or measurement of battery stack voltages as large as
± 36 volts.
The Reference 3000 offers two different compliance voltage and compliance current settings. A user can
choose to operate the Reference 3000 set for compliance of ± 1.5 Amperes and voltages up to ± 30 Volts or
he/she can chose to operate at ± 3 Amperes and voltages up to ± 15 Volts. This setting cannot be changed in
the middle of an experimental run.
Reference 3000 features include:
•
•
•
•
11 decade current auto-ranging,
electrical isolation from earth ground,
switchable compliance current and compliance voltage settings,
current interrupt iR compensation, and
2-1
Chapter 2 -- Introduction--About the Auxiliary Electrometer Option
•
both analog and digital filtering.
A sine wave generator on the Reference 3000 allows its use for impedance measurements at frequencies up to
1 MHz. Data can be acquired at frequencies up to 300,000 points per second, allowing Cyclic Voltammetry at
scan rates of 1500 V/sec with 5 mV per point resolution.
A unique DSP (Digital Signal Processing) data acquisition mode allows the Reference 3000 to reject noise, from
the instrument itself, from the electrochemical cell, and from the lab environment. In many cases where other
instruments require a cell in a Faraday shield to make quiet measurements, the Reference 3000 can be used
with the cell exposed on a bench top.
The Reference 3000 offers an unprecedented combination of high speed, high sensitivity, and low noise. Stateof-the-art analog components were used throughout the design. In all design decisions, performance weighed
more heavily than product cost.
The Reference 3000, like all Gamry potentiostats, requires a computer for its use. Unlike most of Gamry’s
older potentiostats, the Reference 3000 interfaces to the computer through a USB connection. The USB
connection has become truly universal, with USB ports found on all modern computers. Gamry’s software
currently supports up to 16 Reference 3000 Potentiostats connected to one computer.
The Reference 3000 is isolated from earth ground. It can therefore be used to make measurements on cells
that contain an earth grounded metal. A few of examples of such systems include are autoclaves, large metal
storage tanks, stress apparatus, and capillary electrophoresis detectors.
About the Auxiliary Electrometer Option
The Reference 3000 Potentiostat can be equipped with a unique Auxiliary Electrometer option. This factory
installed option is especially useful when you need to measure the performance of individual cells in a multicell fuel cell or battery stack.
Up to eight completely independent voltages can be measured using this option. The measurements are fully
differential, so cell voltages at any point in a stack can be measured. Each input can measure a ±5 volt signal
superimposed on a common mode voltage that can be as large as ± 36 volts! The input impedance is greater
than 1011 Ω, so the inputs can even be connected to small diameter Lugin probes.
This option can be used to simultaneously measure electrochemical impedance on up to eight cells in a cell
stack. This is often of great interest since cells in a fuel cell or battery stack are not identical.
The AE is not restricted to energy conversion and storage applications. The electrometer inputs can measure
virtually any voltage. You can measure voltages from temperature, pressure or strain transducers or voltages of
multiple reference electrodes in a cell.
Notational Conventions
In order to make this manual more readable we have adopted some notational conventions. These are used
throughout this manual and all other Gamry Instruments manuals:
•
Numbered lists. A numbered list is reserved for step-by-step procedures, with the steps always
performed sequentially.
•
Bulleted list. The items in a bulleted list, such as this one, are grouped together because they represent
similar items. The order of items in the list is not critical.
•
File names and folders. Inside paragraphs, references to computer files and Windows folders will be
capitalized and placed within quotes, for example: “C:\MYGAMRYDATA\CV.DTA" and
“GAMRY5.INI".
2-2
Chapter 2 -- Introduction--Notational Conventions
2-3
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Chapter 3 -- Instrument Circuitry
Reference 3000 Schematic/Block Diagrams
If you are not familiar with electronic schematics or potentiostats, you probably want to skip this chapter. This
information is for expert use only and is not required for routine use of the Reference 3000.
The following figures are partly schematic diagrams and partly block diagrams. They are intended to show the
basic principles of the Reference 3000 circuitry without the confusion of the full circuitry details. The
complexity of the Reference 3000 can be quite daunting – the Reference 3000 circuit boards contain more
than 3000 components connected by almost 2500 circuit nets!
The schematic/block diagram figures show:
•
the potentiostat board and heat sink board in a potentiostatic control mode,
•
the control board circuits for signal generation,
•
the control board circuits for signal conditioning and A/D conversion,
•
the Auxiliary ADC channel input switching,
•
the microprocessors in the Reference 3000,
•
DC-DC power conversion,
•
The optional Multi Channel (MCE) circuitry.
3-1
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-1
Reference 3000 Potentiostat Board in Potentiostat Mode
Simplified Schematic/Block Diagram
3-2
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Notes for Figure 3-1
•
The 4x booster following the Control Amp can operate with two combinations of compliance current
and compliance voltage. One is ± 1.5 amps at ± 30 volts, the other is ± 3 amps at ± 15 volts.
•
Only Potentiostat Mode circuitry is shown in this figure. In this mode the voltage difference between
the Reference and Working Sense leads (called Esig) is feedback into the control amplifier.
In Galvanostat Mode, the feedback is from Isig.
In the ZRA and stack modes, the feedback is from a differential amplifier measuring the difference
between the Counter Sense and Working Sense leads of the cell cable. The counter sense circuitry is
not shown. It is conceptually similar to the voltage sensing circuit that generates Esig, except that it can
measure voltage differences as large as ± 36 volts.
•
The Bias DAC and PFIR (Positive Feedback IR compensation) DAC are set using a computer bus that is
not shown.
•
Switches are either reed relays or MOS switches as appropriate. All switches are under computer
control (obviously, since the Reference 3000 does not have a knob and dial front panel).
•
The variable current measurement resistor, Rm, is one of eleven fixed value resistors selected using
relays. The resistor’s values vary by decades: 50 mΩ, 500 mΩ, 5Ω, 50 Ω …500 MΩ. The lower
value resistors require software gain corrections. Correction values are measured at Gamry’s test
facility and stored in an EEPROM on the Reference 3000 potentiostat board. Software calibration of
the instrument by a customer does not change these Rm gain corrections.
•
Other components shown as being variable (IEStab capacitor and CASpeed capacitor) are actually
several fixed value components switched into the circuit, not continuously variable .
•
The monitor BNC connectors for Isig and Esig are lightly filtered using an RLC circuit.
•
The ADC channel for Esig is actually switchable between Esig (the reference voltage minus the working
sense voltage) and Zsig (the counter sense voltage minus the working sense voltage). The Zsig
connection allows the Reference 3000 to measure the voltage of battery or fuel cell stacks.
•
The programmable attenuator on Esig prior to the ADC channel scales the Esig voltage to make it
compatible with the A/D channel’s ± 3 volt input range. The 0.25 gain setting allows the Reference
3000 to measure potential signals slightly in excess of 10 volts (on a 12 volt full scale range). Isig is
gained to be 3 volts full-scale so it does not require a similar attenuation function.
•
All the resistors summing voltages into the Control Amplifier input do not have values shown on the
diagram – their values depend on scaling factors too complex to discuss in this chapter.
•
Calibration components are not shown.
•
Gamry’s software can disconnect the signal generator from the Potentiostat. Once disconnected it can
be used for other experimental control tasks.
•
Overload protection and overload detection are not shown. Good engineering practice demands that
any possible misconnection of the cell leads will not damage the instrument. This practice has been
followed in the Reference 3000 design.
The overload protection can handle overloads of up to 30 amps for very short times. Fuses in the
Working and Counter Sense leads always open up before overload conditions can damage the
instrument. Misconnection of a battery, fuel cell, or super-capacitor stack can open the fuse, but will
not cause hardware failures.
3-3
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-2
Reference 3000 Signal Generation Circuitry
Notes on Figure 3-2:
•
All the resistors summing voltages into the Summing Amplifier input do not have values shown on the
diagram. Their values depend on scaling factors too complex for this simplified diagram.
•
The IR DAC has a ± 8 volt full-scale range.
•
Calibration components are not shown.
•
The DDS can generate fixed amplitude sine waves with frequencies between 1 MHz and 1 mHz. In
practice, Gamry’s EIS300 software uses the Scan DAC to generate sine signals if frequency is below 1
Hz.
The low pass filter removes high frequency distortion in the “raw” DDS output.
The attenuator scales the DDS. The maximum output signal is 5.979 volts peak-to-peak and the
minimum is approximately 11 µV peak-to-peak.
•
The BNC connector for Sig Gen out is lightly filtered using an RLC circuit.
3-4
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-3
One A/D Signal Chain in the Reference 3000
Notes for Figure 3-3:
•
This diagram shows one of three identical ADC channels. One channel is dedicated to measurement
of the potentiostat’s current signal, another is used to measure the cell or stack voltage, and the third is
switched between a wide selection of possible signals. See Figure 3-4
•
All three A/D converters are triggered simultaneously to start a conversion. This trigger and the pulse
updating the Scan DAC voltage are under the control of a hardware state-machine. This insures that all
waveform and data acquisition timing is tightly controlled and reproducible point-to-point.
By default, the data acquisition is synchronized with the 300 kHz power supply switching frequency, to
reduce noise due to the power supply. Data acquisition times that are a multiple of 3.333 µSec will
maintain this synchronization.
•
All analog signals that cross from the Potentiostat Board to the Control Board or vise versa are received
differentially as shown here.
•
The 5 Hz, 1 kHz, and 200 kHz filters are 2-pole Butterworth filters. The 3 MHz RLC filter has an
arbitrary transfer function.
•
All signal channel components are selected for optimal DC accuracy, low noise, and high bandwidth.
3-5
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-4
Aux Channel Input Switching
Notes for Figure 3-4:
•
Two ADC Channels are dedicated to the potentiostat’s voltage and current signals. This diagram shows
the signals that can be connected to the third channel.
•
The Aux ADC BNC input is a differential input. Some of this input’s characteristics can be changed by
either jumpers or CMOS switches. Early Reference 3000’s use jumpers to change the characteristics,
while later units (shipped after the middle of 2009) will use CMOS switches under software control to
change the characteristics. Contact Technical Support at Gamry.com if you are uncertain which type
of unit you have.
Jumper configured Reference 3000’s are shipped configured for input impedance of 100 kΩ and
unfiltered operation. The jumpers shown in this diagram allow it to be configured for high input
impedance and/or input filtering.
•
The thermocouple input allows for connection of a K Type thermocouple. Note that this circuit must
be calibrated to obtain reasonable accuracy. A section of the Reference 3000 calibration procedure
allows for user calibration of this input.
•
The other two inputs to the Aux channel can be used to measure the AE (Auxiliary Electrometer) signal
or a Control Amp voltage signal.
3-6
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-5
Microprocessors in the Reference 3000
Notes for Figure 3-5:
•
Note the lack of a ground connection between the USB bus and the Reference 3000 circuitry.
•
The EasyUSB firmware is loaded into EasyUSB RAM on power-up. The USB firmware can be updated
over the USB via a selection in the Reference 3000 section in the Windows Device Manager.
•
The Power PC firmware is also transferred from ROM into RAM on power-up. The Power PC firmware
can also be updated over the USB via a selection in the Reference 3000 section of the Windows
Device Manager. Time critical sections of the Power PC code are kept in the processor’s fast cache
memory.
•
The term UART refers to a Universal Asynchronous Receiver Transmitter. It converts parallel data to a
self-clocking serial bit stream. The UARTs send data at 6 Mbits/second.
•
The Bus Transceiver isolates bus activity on the Controller and Potentiostat boards. Only reads and
write to locations on these boards generate bus activity. This reduces noise pick-up.
•
Each board in a Reference 3000 has local non-volatile data storage. This is used to save calibration
data and board revision information. Unlike previous Gamry Instruments Potentiostats, the Reference
3000 calibration data is stored in the instrument, not in a data file. When a Reference 3000 is moved
from one computer to another, its calibration remains valid.
3-7
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
Figure 3-6
DC-DC Power Conversion
Notes for Figure 3-6:
•
Note the ground isolation between the input power and the Reference 3000 circuitry. The Reference
3000 chassis is connected to the Floating Instrument Ground. Transformers and isolators are the only
components connected between the grounds.
•
The 300 kHz power supply sync signal is derived from the same clock used to control data acquisition.
Data points taken at an integer multiple of 3.333 µSec/point will be synchronized with the power
supply, minimizing the effect of power supply noise on the data.
•
Additional circuitry that is not shown protects the Reference 3000 against ESD (electrostatic discharge)
and electrical surges. Note that the Reference 3000 is also protected against damage if an incorrect
polarity power input is connected to the unit.
WARNING
Do not use a DC power source other than the AC adapter model provided with your
Reference 3000. Other replacements may void the performance and/or safety
characteristics of the Reference 3000.
•
The incoming DC voltage must be between 22 and 26 volts. With inputs below 22 volts, the PWM
(Pulse Width Modulator) may be unable to regulate the supply. Above 26 volts, the PWM may not
start-up.
3-8
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
CAUTION
Power input voltages less than 20 volts or greater than 26 volts can damage the
Reference 3000’s power supply.
Figure 3-7
One AE Channel
Notes for Figure 3-7:
•
One of eight identical channels is shown
•
The input buffers work over the entire Reference 3000 compliance voltage range.
•
The maximum useable differential voltage between the two inputs on a channel is ± 5 volts.
•
Each channel has its own filtering. The Aux A/D Channel filter is not useful for switched inputs.
•
The x10 and x100 gains in the Aux A/D channel can be used to improve A/D resolution.
•
The inputs have an input impedance of greater than 1011 Ohms as long as the product is powered.
•
The inputs will not be damaged by connection to voltages as large as ± 36 volts versus the Reference
3000’s ground, regardless of the compliance voltage setting. This is true even when the Reference 3000 is
not powered up. They cannot measure voltages larger than the compliance voltage.
3-9
Chapter 3 -- Instrument Circuitry--Reference 3000 Schematic/Block Diagrams
3 - 10
Chapter 4 -- Installation--Reference 3000 Schematic/Block Diagrams
Chapter 4 -- Installation
This chapter of the Gamry Instruments Inc. Reference 3000 Operator's Manual covers normal installation of the
Reference 3000. We assume the Reference 3000 is installed as part of a Gamry Framework based
electrochemical measurement system containing a Microsoft Windows compatible computer.
These instructions assume use with Gamry's Framework Software Revision 6.0 or higher.
Figure 4 - 1
Front View of a Reference 3000 without AE Option
4-1
Chapter 4 -- Installation--Initial Visual Inspection
Initial Visual Inspection
WARNING
If the Reference 3000 is taken from a cold location (for example outdoors in winter
conditions) to a warm humid location, water vapor could condense on the cold
surfaces inside the Reference 3000, possibly creating a hazardous condition. The
“reinforced insulation” that keeps the operator from accessing the “hazardous live”
voltages in the Reference 3000 can be rendered ineffective if the Reference 3000 has
condensed water inside its case. Before connecting power to a “cold” Reference
3000, allow at least two hours for the Reference 3000 to warm at room temperature.
After you remove your Reference 3000 from its shipping carton, you should check it for any signs of shipping
damage. If any damage is noted, please notify Gamry Instruments, Inc. and the shipping carrier immediately.
Save the shipping container for possible inspection by the carrier.
WARNING
The “reinforced insulation” that keeps the operator from accessing the “hazardous
live” voltages in the Reference 3000 can be rendered ineffective if the Reference 3000
is damaged in shipment. See Chapter 1 for more details. Do not operate damaged
apparatus until a qualified service technician has verified its safety. Tag a damaged
Reference 3000 to indicate that it could be a safety hazard.
Physical Location
You normally locate your Reference 3000 on a flat workbench surface. You will want to have access to the rear
of the instrument because some cable connections are made from the rear. The Reference 3000 is generally
operated in an up-right position (see Figure 4-1). Operation in other positions is possible as long as you insure
that air movement through the chassis is not restricted.
CAUTION
Do not block the airflow into or out of the Reference 3000 chassis. While the circuitry
should shut down if subjected to excessive heat, the Reference 3000 enclosure may
become uncomfortably hot to the touch if no air flows through the chassis. Running
the Reference 3000 without adequate cooling could shorten the time-to-failure of
some of the circuitry.
If you do place your Reference 3000 within an enclosed space, make sure that the internal temperature within
that space does not exceed the 45°C ambient temperature limit of the Reference 3000. Be particularly careful
if a computer or other heat dissipating equipment is mounted in the same enclosure as the Reference 3000.
The Reference 3000 has not been designed for outdoor use.
4-2
Chapter 4 -- Installation--Computer Requirements
Computer Requirements
Before you connect a Reference 3000 to a computer you must make sure that your computer meets these
simple requirements.
•
One of the following Operating Systems: Windows XP™ Service Pack 3 or higher, Windows Vista™ 32or 64-bit, or Windows 7™32- or 64-bit.
•
A USB port that supports high speed (480 Mbits/second) USB 2.0 transfers.
Gamry's Windows-based application software packages may impose additional, more stringent requirements.
See the software documentation or contact a Gamry representative for details.
Quick Start Guide for System Installation
Your shipment should have included a short document entitled: Quick Start Installation Guide - USB
Potentiostat. It contains the latest instructions for installing Gamry hardware and software onto a computer
system. If this document is missing, the following information should be sufficient for you to install the Gamry
Framework Software and Gamry Potentiostat onto your computer.
Software Installation
The Reference 3000 is compatible with the Windows Plug & Play configuration system. Like most Plug & Play
hardware, it is best if you install the software for the Reference 3000 before you install the potentiostat
hardware.
Gamry Software Setup program will normally start automatically when you place the Gamry Instrument’s
Software CD (or Gamry Instrument Software Flash Drive) into your computer.
If you have inserted the Gamry CD or Flash Drive into your computer and the Gamry Setup program does not
start automatically:
1) Navigate to the root folder of the device containing the Gamry Software (CD or Flash Drive) or to a
Windows folder containing the Gamry Software.
2) Run the program called Autorun.exe found in this folder.
If you do not know how to navigate to the Gamry Installation device, consult your local computer expert or
network administrator or email [email protected]
Autorun.exe will run a Setup program. In most cases, you can choose the default choices or the most obvious
choices on all screens shown during the Setup process. When the “Select Features” screen appears you will
see a list of applications (eg DC105, PHE200, ESI300). Make sure that you select all the applications that have
been purchased with your system.
Reboot your Computer after Software Installation
You should reboot your computer once the Gamry Setup program is done. The Setup program will normally
offer you the opportunity to do so. USB device drivers are usually loaded when Windows boots up. Following
Setup, you may not be able to use your Reference 3000 until the drivers are loaded.
Note
Device Driver Installation may not occur until a while after the Windows Desktop screen
appears. On a slow computer, or a busy computer with lots of applications, the delay
before driver installation can be a minute or more.
4-3
Chapter 4 -- Installation--Power Cord and Power Connection
Figure 4 - 2
Rear Panel of the Reference 3000
Power Cord and Power Connection
The Reference 3000 does not plug directly in the AC mains supply. Instead, the mains are connected to an
external power supply, which supplies a regulated 24-volt DC output. This regulated DC is then connected to
the DC power input jack on the rear of the Reference 3000 (see Figure 4 - 2).
The external power supply provided with the Reference 3000 is rated for operation from 100 to 240 Vac, at
frequencies from 47 to 63 Hz. It should be useable worldwide.
CAUTION
If your facility owns both Reference 600’s and Reference 3000’s, you must insure that
the smaller power adapter from the Reference 600 is not used to power a Reference
3000. The Reference 3000 will not power up with the smaller adapter. Fortunately,
neither the Reference 3000 nor the small power adapter will be damaged if connected
in error.
The power adapter for the Reference 3000 is almost 18 cm long. All dimensions on
the Reference 600 power adapter are below 11 cm.
The Reference 3000 external power supply is delivered with a line cord suitable for use in the United States. In
other countries, you may have to replace the line cord with one suitable for your electrical outlet type. You
must always use a line cord with a CEE 22 Standard V female connector on the apparatus end of the cable.
This is the same connector used on the US standard line cord supplied with your Reference 3000. See
Chapter 1 for specific safety information regarding line cord selection.
4-4
Chapter 4 -- Installation--Power Up Test
Power Up Test
Before you make any other connections to your Reference 3000 you should check that the Reference 3000 is
at least nominally functional.
One quick test is to power up the Reference 3000 and watch the blue power LED indicator on the front panel
of the Reference 3000 (see Figure 4 - 1). After connecting DC power to the Reference 3000, turn on its rear
panel Power switch (see Figure 4 - 2). The Power LED should go on for a second or so, flash three times, then
remain on.
The status of the other LED indicators is not important at this time.
Each flash of the power LED upon startup corresponds to successful conclusion of one portion of the Power
PC’s power-up self-test.
If the power LED goes on, then turns off and stays off, the Reference 3000 is not working properly! Contact
Gamry Instruments or your local Gamry Instruments representative as soon as possible if this power up test fails.
USB Cabling
The Reference 3000 connects to the computer using a standard High Speed USB A/B cable. A suitable cable
was shipped with your Reference 3000. If this cable has been lost, you can get a replacement at almost any
computer retailer. The replacement cable should be rated for USB 2.0 high speed USB operation.
An A/B USB cable has different connectors on each end. The end with a wider, rectangular shaped connector
plugs into a USB port on your computer (or a similar port on a USB hub). The end with a nearly square
connector plugs into the USB port on the Reference 3000 (see Figure 4 - 2).
The USB connection can be “hot-plugged”. This means, both the computer and the Reference 3000 can be
powered-up before the USB cable is plugged in. Unlike many other instrument system connections, you need
not power down the system before plugging in the USB.
You can also safely remove the USB cable without powering down the Reference 3000 and your computer.
Be aware however, that this may have undesirable consequences if the system is currently taking data or
performing an electrochemical experiment.
Front Panel USB LED
The front panel USB LED provides a simple test of two aspects of normal Reference 3000 USB operation. It has
three normal states:
•
Unlighted - indicating that the USB cable is disconnected or the USB connection is disabled by the host
computer,
•
Solid Green - indicating that a valid cable connection has been made and the Reference 3000 USB
processor is receiving power from the USB cable,
•
Flashing Yellow - indicating that valid USB messages are being transferred between the computer and
the Reference 3000.
The flashing state will only be seen when Gamry Instruments application software is running.
One additional USB LED indication is possible. A solid red indication occurs during a firmware update. The
firmware update process is described later in this chapter.
4-5
Chapter 4 -- Installation--1st Time Device Installation in Windows XP
1st Time Device Installation in Windows XP
Note
These instructions presume you have already installed Gamry software Revision 6.0 or
higher.
Windows 7 Users: The dialog boxes in this section of the manual will not be displayed. Please skip to the
next section of the manual, Running the Framework to continue the installation process.
Windows XP or Vista Users, the message that will appear is something like “New device found” or “Unknown
USB device Detected”. The next screen that looks something like this:
You should see a screen that looks something like this:
Figure 4 - 3
Welcome to the Found New Hardware Wizard
As shown in this Figure, do not choose to let Windows Update find the device driver that you need. The
Windows Update web site has no knowledge of the Gamry Instruments Reference 3000.
Make sure you select No, not this time. After you select, Next, you should see a screen that looks like this:
4-6
Chapter 4 -- Installation--
Figure 4-4
Install the Software Automatically
All Gamry device drivers are pre-installed on your computer disk drive during the software installation process.
Select Install the software automatically, then select Next.
These messages will also be seen when an Reference 3000 instrument is moved to a new USB port. In this
case, you can still select Install the software automatically, even if you do not have the Gamry Instruments
CD. The driver that was previously installed on your computer’s disk drive will be used.
The Windows Device Manger will locate and install the required files, which are already on your system.
Running the Framework
Regardless of your electrochemical application, Gamry recommends running the Gamry Framework after you
install new Framework software or add a potentiostat to your system. The Framework Instrument Manager
allows you to:
•
•
•
•
Rename potentiostats,
Calibrate potentiostats,
Manage potentiostat firmware,
Authorize Specific Applications for use with Specific Potentiostats
You run the Gamry Framework by clicking on the icon it installed on the Windows desktop. You can connect
and power any Gamry potentiostats either before or after you start the Framework.
4-7
Chapter 4 -- Installation--Framework Device Status Bar
Framework Device Status Bar
By default, the Gamry Framework shows a Device Status Bar under its main menu: see Figure 4-5. If you don't
see the Device Status Bar when you run the Gamry Framework, it has been disabled in the Framework Options
menu.
Potentiostat Devices (instruments) that are connected to the computer appear on this bar. The round indicator
associated with each device shows its status:
Green
The device is available to run experiments
Yellow
The device is currently running an experiment
White
The device is connected to the system, but is not usable. This is generally the result of a revision
mismatch between the Framework software and the device's firmware. You can use the
Framework Instrument Manager to fix the mismatch.
The screen capture below shows a Framework screen with three USB instruments connected.
Figure 4-5
Framework With Three Potentiostats and One Running Test
The Interface 1000 (IFC 01004) in this system is shown with a green indicator because it is installed and ready
to run. The Reference 600 labeled My Ref600 has a yellow indicator because it is recording the EIS spectrum
shown on the screen. The Reference 600 labeled Jims Ref600 has a white indicator, showing it is plugged in
but cannot be used. This is an indication of obsolete firmware.
Though no Reference 3000 was used in this example, its status indicator behaves in the same manner
described above.
4-8
Chapter 4 -- Installation--Gamry Instrument Manager
Gamry Instrument Manager
You can use Gamry's new Instrument Manager dialog box to make changes to the configuration of your
Reference 3000 system. This dialog box is accessed through the Options menu in the Gamry Framework.
The Instrument Manager is used to:
•
•
•
•
•
Rename potentiostats
Delete potentiostats that are not currently connected to the computer
Select the order in which potentiostats appear in menus
Authorize potentiostat use with applications packages
Update firmware within potentiostats
You run the Instrument Manger by selecting Options, Instrument Manager... on the Framework Menu.
Figure 4-6 shows the Instrument Manager dialog box for the three potentiostat Framework session shown in the
previous section.
Figure 4-6
Instrument Manager Dialog Box
Each Gamry potentiostat in the system appears on a separate row. All Gamry Instruments potentiostats that are
known to the system are displayed in the Instrument Manger. An instrument is selected by clicking anywhere
within that row for that instrument. Selecting an instrument that is connected and idle will blink its Power LED.
The buttons on the right side of the dialog box change depending on which instrument is selected. Some
buttons are inappropriate for some instruments.
The Status column tells you the whether each instrument is available and usable by the Framework. Possible
status conditions are:
Present
The instrument is connected, powered, and available for use.
Absent
The instrument was connected in the past but is currently not connected or not powered.
Instruments with this status can be deleted from the system
In Use
The instrument is currently running a Framework experiment.
Update
The instrument is connected and powered, but cannot be used to run experiments. Its current
firmware revision is not compatible with the current Framework revision. You can update the
instrument's firmware by selecting this instrument and selecting Firmware Update.
4-9
Chapter 4 -- Installation--Authorization Codes and Label
You can delete an Absent instrument by selecting Delete when an instrument is selected. Deleting an
instrument simplifies the Instrument Manager dialog box. It has little effect otherwise; the deleted instrument
can be reconnected later.
When you setup an experiment, you will need to select the potentiostat used to run the test. The instruments
will appear in the order shown in the Instrument Manager, with the device in the top row displayed first. The
Up and Down buttons allow you to move a device in the dialog box and change the order in which devices are
displayed.
Authorization Codes and Label
If you purchase additional Gamry application software or you need to make a correction to your authorization
codes, you can do so using the Windows Device Manager or the Framework Instrument Manager.
The dialog box used to enter authorization codes also allows you to change the Label for your device. The
Gamry Framework Application Software must be closed before you can use the Device Manager to make
changes. Next, you must select the appropriate device, as discussed in the Device Manager and Instrument
Manager discussions above. In the Windows Device Manager, once you have selected the appropriate device,
right click and select Properties. Next, select Device Settings and you will see a screen that looks like Figure
4-7:
4 - 10
Chapter 4 -- Installation--Authorization Codes and Label
Figure 4-7
Device Settings Tab
This was the Device Settings dialog box for the second potentiostat in the system described above. You can
enter or edit any of the authorization codes or Label for the device by clicking on the appropriate edit box and
entering the in formation. In the Figure above, the default label has been changed to a friendly name - My
Ref600.
To enter an authorization code, simply click on the Add button. A dialog box will appear as shown in Figure
4-8. You enter the package name, such as “EIS300”, followed by the 10 digit authorization code.
4 - 11
Chapter 4 -- Installation--Firmware Update
Figure 4-8
Enter an Authorization Code
Press OK when you are finished.
On occasion you may have to change the USB port used to connect your Reference 3000 to your computer.
The Windows Device manager will interpret a Reference 3000 on a new USB port as a new Reference 3000.
Firmware Update
Your Reference 3000 was shipped with the latest version of its firmware. From time to time, Gamry makes
changes to the instrument's Firmware code, and a firmware update will be required to make use of the new or
improved code.
There are two firmware images that can be field updated on your Reference 3000. The first is the Instrument
Firmware. This is the program that handles most of the functionality of the Reference 3000. The second is the
Communications Firmware. This program handles the USB communications between your Reference 3000
and the host computer
Appropriate update files (firmware images) can be obtained from the Gamry Instruments website at
www.gamry.com. Download the file containing the new image and save it onto your computer’s hard disk.
Alternatively, every Gamry Software CD (or Gamry Software Flash Drive) contains a firmware folder that
contains firmware files compatible with that CD’s Framework revision.
You can initiate the Firmware Update process using the Framework Options, Instrument Manager...
command or using the Windows Device Manager. The Instrument Manager is the preferred method.
To update any of the Firmware, you must first select the appropriate device in the Instrument Manager, as
discussed in the Device Manager section. Once you have selected the appropriate device, right click and select
Properties. Next, select Firmware Update and you will see a screen that looks like Figure 4-9:
4 - 12
Chapter 4 -- Installation--Firmware Update
Figure 4-9
Firmware Update Tab
Depending upon which code you wish to update, click on Update Instrument Firmware or Update
Communications Firmware. You will then be prompted for a file. Navigate to the file’s location (on the
Gamry software CD or on your computer’s hard drive) and then press Open. The update procedure will
begin. A status bar shows the progress of the update. The USB indicator on the Reference 3000 should also
turn red during the procedure. Once the update is successful, press OK and your Reference 3000 will be ready
for use.
Once again, appropriate update files can be obtained from the Gamry Instruments website at www.gamry.com.
Should you encounter a problem updating the firmware in your Reference 3000, please contact Gamry
Instruments for assistance.
Interrupting a firmware update can cause a catastrophic failure of your system. Do not turn off the Reference
3000, do not unplug the USB cable, and do not stop the host computer operation when the USB LED is a
steady red color.
Caution
Do not interrupt a firmware update that is in progress. An incomplete update can render
a Reference 3000 inoperable until it is returned to Gamry for reprogramming.
4 - 13
Chapter 4 -- Installation--
Calibration
You should calibrate each potentiostat installed in your system. A calibration script is provided with the Gamry
Framework. The Installation Manual for every major application package contains instructions for calibration
using this script.
The calibration for the Reference 3000 has been divided into three sections: DC Calibration, AC Calibration,
and Low I DC Cal. All three calibration procedures are accessed via the Utility selection on the Framework’s
Experiment pull down menu.
Separate Calibration for Each Reference 3000 Cable Type
The Reference 3000 recognizes the type of cable connected to its cell connectors. It maintains a separate AC
calibration table for each type of cable. The Gamry Framework will not let you use AC calibration data
recorded using a 60 cm shielded cable for experiments run using a longer cable.
DC and AC Calibration
These two procedures use an external resistive dummy cell.
CAUTION
Reference 3000 calibration calls for an external resistive dummy cell. Your Reference
3000 was shipped with a Universal Dummy Cell 4, which includes a 2 kΩ
Ω, 0.02%
accurate resistor in the position marked “Calibration”. After calibration, please place
this dummy cell in a safe place where you can find it if your unit requires
recalibration.
If you do need to recalibrate and you cannot find your Universal Dummy Cell 4, you
can perform DC Calibration using a different 2 kΩ
Ω resistor. Its wattage is
unimportant. Some performance checks in the calibration process may fail if the
resistors inaccuracy exceeds 0.2% (4 Ω).
We do not recommend AC Calibration with any resistor other than the one on the
Universal Dummy Cell 4. The Universal Dummy Cell 4 was designed to separate the
working electrode leads from the counter and reference electrode leads. If you
perform AC Calibration without adequate separation between these leads, you will see
phase shift in your high frequency EIS data. 1.4 pF of stray capacitance across a 2 kΩ
Ω
resistor causes a 1°° phase shift at 1 MHz.
The resistor used for calibration should be enclosed in a Faraday shield during the calibration process. The
Faraday shield should be connected to the black lead on the standard cell cable. A Faraday shield suitable for
calibration is included in every Reference 3000 shipment.
Earth grounding the Reference 3000 is also recommended during calibration, but is not essential.
4 - 14
Chapter 4 -- Installation--Calibration
Potentiostat calibration is only required infrequently. You should recalibrate your Reference 3000 under the
following circumstances:
•
•
•
•
It has been about one year since your last calibration.
Your potentiostat has been serviced.
You notice breaks or discontinuities in the data curves recorded with your system.
The system is being run in an environment that is very different from the previous operating
environment. For example, if the Reference 3000 was calibrated at 15 °C and you are now
operating it at 30 °C, you should recalibrate.
Low I Range DC Calibration
The standard Reference 3000 calibration is performed with the cell leads connected to a 2 kΩ resistor. During
the calibration procedure, DC current range offsets are recorded with the cell switch turned off. A DC current
measurement is made on each of the 11 current ranges in the Reference 3000. The measured current on each
range is the sum of current contributions from:
•
•
•
•
•
The input current of the I/E Converter input amplifier,
the input current of the Working sense input amplifier,
the input current of the Reference input amplifier,
the input current of a Counter Sense input amplifier,
current leakage in the cell switch.
In most real-world experiments, the cell is turned on, and the I/E converter does not measure the last three
terms listed above. These currents still exist, but they are generally sourced by the low impedance counter
electrode lead. During Low I DC Calibration the first two terms are directly measured in order to improve pA
accuracy of the instrument.
The current contributions from each source on the above list are (at most) a few pA, so they are insignificant on
all but the most sensitive Reference 3000 current range – the 300 pA range.
This effect can cause differences of up to 8 pA between DC current measured with the cell turned off and
current measured with the cell turned on. In most cases the difference is smaller – one or two pA.
Only two Reference 3000 applications are sensitive enough that this current measurement offset causes
problems. One is Physical Electrochemistry (Cyclic Voltammetry for example) with small electrodes and the
second is EIS on high impedance samples such as barrier coatings. Incorrect DC current readings in EIS can
slow the experiment, since the automatic ranging algorithms in the EIS300 software can make poor range
choices given incorrect data. This can significantly lengthen the time needed to measure an EIS spectrum.
Most corrosion experiments or macro-electrode measurements involve currents much too large to be affected
by this difference.
The Gamry Framework now includes a special “Low I DC Current” calibration procedure that corrects the
Reference 3000 offsets to minimize this problem. The procedure uses a script that:
1)
asks you to disconnect the reference, counter, and counter sense leads from the calibration cell,
2)
measures the I/E input and Working sense amp input currents on the 300 pA range,
3)
replaces the 300 pA current range offset measured in the full DC calibration with the improved value.
4 - 15
Chapter 4 -- Installation--Calibration
The error sources listed above are both time and temperature dependent, so we recommend frequent “Low I
DC Calibration” - if you need accurate measurement of absolute currents at pA levels. The procedure runs
fairly quickly, so daily or weekly calibration should not be too inconvenient.
NOTE
The Low I DC Calibration is not a full calibration. You must run a full DC Calibration on
your Reference 3000 before you first run the “Low I DC calibration”. Remember that the
Reference 3000 must have a full DC calibration on the same type of cable you are using
for the Low I DC Calibration.
4 - 16
Chapter 5 -- Cell Connections--Cell Cable Overview
Chapter 5 -- Cell Connections
Cell Cable Overview
The Cell Connectors are two 15-pin D-connectors on the front of the Reference 3000.
The upper (female) connector is labeled Counter/Working. It carries the cell current between the Counter
electrode wire and the Working electrode wires and the instrument
The lower male connector is labeled Sense Inputs. It contains only high impedance inputs used to sense
potentials in the cell.
Gamry’s standard cell cables always come in pairs. Each cable has a D-connector on one end and a number of
leads to connect to electrodes in an electrochemical cell. The D-connector end of the cable is connected to the
appropriate D-Connector on the front of the Reference 3000. The male and female cables cannot be
interchanged.
Every Reference 3000 is shipped with a pair of standard shielded cell cables. The Gamry part numbers for
these cables are 985-85 and 985-90. They are both 60 cm complex cables, with D-connectors on one end a
color coded banana plugs and/or pin sockets on the other end.
In some cases, your system may also include special purpose cell cables. The special purpose cell cables will
include documentation describing their use.
You should always screw both cell cables into place since cables can fall off the unit. This can be disastrous if it
occurs during an experiment.
Ancillary Apparatus
Do not use the Reference 3000 with ancillary apparatus connected directly to any of the cell leads. Examples
of ancillary apparatus include DVMs, oscilloscopes, chart records, and data loggers. Ammeters and voltmeters,
regardless of their specifications, almost always create problems when connected to the Reference 3000 cell
leads. Ancillary measurement devices can be connected to monitor points on the rear panel of the Reference
3000.
AE Connections
The AE (Auxiliary Electrometers) is an option for the Reference 3000. Its inputs often connect to an
electrochemical device, such as a battery or fuel cell stack. The inputs can also connect to external
measurement devices, such as a pressure sensor.
AE connections are not described here. See Chapter 7 for AE connection information.
Fuses in the Cell Cable
The Reference 3000 could be damaged if currents much larger than 3 amps were to flow into or out of the
Counter electrode or Working electrode leads. Improper connection to a battery, fuel cell, or super capacitor
could cause this type of damaging current to flow. All Reference 3000 Counter/Working cell cables contain
fuses in the cable that will protect the instrument if it is misconnected. A later section of this manual discusses
the fuses and their replacement.
Normal Cell Connections
This section assumes that you are using standard, shielded cell cables. This information does not depend of the
length of the cables.
The cell end of the standard cell cables terminates in a number of banana plugs and two pin jacks. Each
termination comes with a removable alligator clip. Table 5-1 identifies the terminals of the cables.
5-1
Chapter 5 -- Cell Connections--Normal Cell Connections
Table 5-1
Cell Cable Terminations - Potentiostat and Galvanostat Modes
Color
Type
Name
Normal Connection
Blue
Banana Plug
Working Sense
Connect to working electrode
Green
Banana Plug
Working Electrode
Connect to working electrode
White
Pin Jack
Reference
Connect to reference electrode
Red
Banana Plug
Counter Electrode
Connect to counter electrode
Orange
Banana Plug
Counter Sense
Used in ZRA mode - connect to counter electrode
Black
Pin Jack
Floating Ground
Leave open or connect to a Faraday shield
Connect both the blue and green cell leads to the working electrode. The working electrode is the electrode
being tested. The blue pin jack connection senses the voltage of the working electrode. The green working
electrode connection carries the cell current. The working electrode may be as much as 250 mV above the
circuitry ground (floating ground).
Connect the white pin jack to the cell's reference electrode, such as an SCE or Ag/AgCl reference electrode.
The measured cell potential is the potential difference between the blue and white cell connectors.
If the instrument is connected in stack mode and the reference input is not used, it should be connected to the
floating ground wire. A pin plug shorting bar is provided for this purpose.
You may need to connect the Reference 3000 to a two terminal device (such as a commercial battery). In this
case, you connect both the white cell and red cell leads to one side of the device and the blue and green cell
leads to the other side. Try to connect the white and blue leads as close to the device as possible.
Connect the red banana plug to the counter or auxiliary electrode. The counter electrode is usually a large
inert metal or graphite electrode. The counter electrode terminal is the output of the Reference 3000's power
amplifier.
The orange lead is only used in ZRA mode and Stack Mode where it senses the counter electrode potential (see
following section). Automatic switching to ZRA mode is possible if this lead is connected to the counter
electrode. If you will not be using ZRA or Stack mode, this lead can be left open or connected to the Counter
electrode.
The black pin jack is connected on the Reference 3000 end to Floating Ground. This is the circuitry ground for
the analog circuits in the Reference 3000. In most cases, this terminal should be left disconnected at the cell
end. When you do so, take care that its metal contact does not touch any of the other cell connections.
If your cell is a typical glass laboratory cell, all of the electrodes are isolated from earth ground. In this case, you
may be able to lower noise in your data by connecting the Reference 3000’s Floating Ground to an earth
ground.
CAUTION
If any electrode in your cell is at earth ground, you must not connect the Reference 3000
chassis to earth ground. Autoclaves, stress apparatus, and field measurements may
involve earth grounded electrodes.
A binding post on the rear panel of the Reference 3000 is provided for this purpose. A water pipe can be
suitable sources of earth ground.
5-2
Chapter 5 -- Cell Connections--ZRA Mode Cell Connections
WARNING
Make sure that your earth ground connection is made to a legitimate source of earth
ground. Consult a qualified electrician if you are uncertain how to obtain an earth
ground. Connecting the Reference 3000 to an incorrect and unsafe voltage can create a
safety hazard (see Chapter 1 for details).
If you are measuring very small currents, you may find that a metal enclosure completely surrounding your cell
(a Faraday shield) significantly lowers measured current noise. This Faraday shield should usually be connected
to both earth ground and Floating Ground. The Floating ground on the black cell lead is a convenient source
of ground.
If any electrode in your cell is connected to earth ground, you should only connect your Faraday shield to the
black cell lead (Floating Ground).
The alligator clip on any cell connection can be removed to access the underlying banana plug or pin jack. If
you need to permanently change the terminations on your cell cable, feel free to remove the banana plugs and
replace them with your new termination. Gamry Instruments can also provide additional standard or special
cell cables.
ZRA Mode Cell Connections
The Reference 3000 can function as a precision Zero Resistance Ammeter (ZRA). It maintains two metal
samples at the same potential and measures the current flow between the samples. It can also measure the
potential of the samples versus a reference electrode.
The cell cable connections for ZRA mode are shown in Table 5-2. Note that the connections are very similar to
those for the potentiostat and galvanostat modes. A second working electrode is substituted for the counter
electrode and the Orange Counter Sense lead must be connected.
Table 5-2
Cell Cable Connections for ZRA Mode
Color
Type
Name
Normal Connection
Blue
Banana Plug
Working Sense
Connect to metal sample #1
Green
Banana Plug
Working Electrode
Connect to metal sample #1
White
Pin Jack
Reference
Connect to a reference electrode
Red
Banana Plug
Counter Electrode
Connect to metal sample #2
Orange
Banana Plug
Counter Sense
Connect to metal sample #2
Black
Pin Jack
Floating Ground
Leave open or connect to a Faraday shield
The counter sense and the working sense lead are each connected to different metal samples. In the ZRA
mode the Reference 3000 is normally programmed to maintain zero volts between these leads. It therefore
maintains the two metal samples at the same voltage.
The white pin jack on the cell cable is normally connected to a reference electrode. The potential between
this lead and the working sense lead is reported as the cell potential.
5-3
Chapter 5 -- Cell Connections--Stack Mode Cell Connections
If the instrument is connected in stack mode and the reference input is not used, it should be connected to the
floating ground wire. A pin plug shorting bar is provided for this purpose.
If you don’t have a reference electrode in your cell, we recommend that you connect the white reference lead
to the working electrode. In theory, the measured potential will be exactly zero when this is done. In practice,
A/D noise and offset will create a small potential signal with a value very close to zero.
Stack Mode Cell Connections
Batteries, fuel cells, and super-capacitors are often connected with several individual cells connected in series to
allow higher voltage operation. This type of connection will be referred to as a Stack connection . Special
experiment scripts allow the Reference 3000 to control and measure stack voltages as large as its compliance
voltage (±15 volts or ±30 volts). These scripts will refer to Stack Mode cell connections. The cell connections in
Stack Mode differ from those in Potentiostatic and Galvanostatic modes.
Voltages in Stack mode are measured as the voltage difference between the Counter Sense input and the
Working Sense Input. A special high-voltage electrometer allows the orange lead to operate at high voltage and
still draw minimal current from the system under test.
Connections in Stack mode are very similar to ZRA mode. The cell cable connections for Stack mode are
shown in Table 5-3.
Table 5-3
Cell Cable Connections for ZRA Mode
Color
Type
Name
Normal Connection
Blue
Banana Plug
Working Sense
Connect to first end of a stack.
Green
Banana Plug
Working Electrode
Connect to first end of a stack.
White
Pin Jack
Reference
Can be connected to a reference electrode
Red
Banana Plug
Counter Electrode
Connect to the second end of a stack
Orange
Banana Plug
Counter Sense
Connect to the second end of a stack
Black
Pin Jack
Floating Ground
Leave open or connect to a Faraday shield
The Counter Sense and the Counter leads are connected to one end of a stack. The Working and the Working
Sense leads are connected to opposite ends of a Stack.
The white pin jack on the cell cable can be connected to a low voltage point in the stack. Some Gamry scripts
allow the voltage difference between the white and blue leads to be read, even though the Reference 3000 is
in Stack Mode.
If the instrument is connected in stack mode and the reference input is not used, it should be connected to the
floating ground wire. A pin plug shorting bar is provided for this purpose.
If you don’t have a reference electrode in your cell, we recommend that you connect the white reference lead
to the working electrode. In theory, the measured potential will be exactly zero when this is done. In practice,
A/D noise and offset will create a small potential signal with a value very close to zero.
Membrane Cell Connections
The Reference 3000 can be used with membrane cells. In this type of cell, a membrane separates two
electrolyte solutions. Two reference electrodes are used - one in each electrolyte. Each electrolyte also
5-4
Chapter 5 -- Cell Connections--Fuses in the Cell Cable
contains a counter electrode. The Reference 3000 controls the potential across the membrane. Table 5-4
shows the cell connections used with a membrane type cell.
Table 5-4
Cell Cable Connections for a Membrane Cell
Color
Type
Name
Normal Connection
Blue
Banana Plug
Working Sense
Connect to reference electrode #1
Green
Banana Plug
Working Electrode
Connect to counter electrode #1
White
Pin Jack
Reference
Connect to reference electrode #2
Red
Banana Plug
Counter Electrode
Connect to counter electrode #2
Orange
Banana Plug
Counter Sense
Leave open (only needed in ZRA mode)
Black
Pin Jack
Floating Ground
Leave open or connect to a Faraday shield
Note that reference electrode #1 and counter electrode #1 must be on one side of the membrane and
reference electrode #2 and counter electrode #2 must be on the other side.
Fuses in the Cell Cable
All standard Reference 3000 Counter/Working cell cables include fuses in the current carrying leads. These
fuses protect the instrument from the extremely large currents that can flow through an improperly connected
electrochemical energy generation or storage device (including batteries, fuel cells, and capacitors). For
convenience, the term battery will be used here to refer to all single-cell or stacked electrochemical devices that
can source energy.
Grounding errors on a battery can be particularly dangerous, since they can result in the battery being shorted
through the instrument. During the development of the Reference 3000 several prototype instruments,
without fuses, were damaged when connected to a Li-Ion battery stack.
NOTE
The fuses in the Reference 3000 Counter/Working cell cable do not protect against a
safety hazard. They are needed to prevent damage to the instrument if it is improperly
connected.
Both the counter electrode lead and the working electrode lead must be fused. Two different cell cable fuse
arrangement have been built or are planned.
In-line Fuse-Holders and Fuses
The In-line fuse design is provided with Counter/Working cable supplied with early Reference 3000 shipments.
The fuses in the cable are located plastic and brass fuse-holders located in-line with the current carrying leads,
as shown in Figure 5-1. The photograph in this Figure shows the Working and Counter electrode leads with inline fuse-holders. The Counter electrode fuse-holder has been opened to show the fuse. The fuse-holder
contains a hidden spring that keeps the fuse in contact with the cell lead.
NOTE
Always turn off the Reference 3000 and disconnect both ends of the Counter/Working
cable before checking or replacing the fuses in the cable.
In this fuse arrangement, the fuse can be removed from the cable by unscrewing the brass knurled nut on the
fuse holder, just below the banana plug. Once a fuse has been removed, it can be checked using an
5-5
Chapter 5 -- Cell Connections--Fuses in the Cell Cable
ohmmeter, such as that found on modern digital voltmeters. Do not trust a visual inspection of the fuse. A
blown (open) fuse should always have a resistance of greater than 100 Ohms. The resistance of a good fuse is
very small.
Figure 5-1
Open Fuse-holder Showing Fuse
Four replacement fuses should accompany every cell cable shipped by Gamry Instruments. The Gamry
Instruments Part Number for the in-line fuses is 630-00019. If you need to source replacement fuses locally,
we currently only recommend Fast Acting (FF), 3.15 amp, 5x20mm cylindrical fuses from the Bussman
Corporation. The Bussman Part Number is BK/GMA-3.15-R. Fuses with similar ratings from other
manufacturers have not been tested, so we cannot recommend their use.
CAUTION
Always replace the fuses in a Reference 3000 cable with the recommended
fuse. Use of improper fuse, especially a fuse with a higher current rating,
could cause instrument failure if a battery cell is improperly connected. Use
of a non-approved fuse will void Gamry’s factory warranty.
Fuses Located in the Cable Hood
The in-line fuses in the Counter/Working are expensive and large enough to be awkward, especially when low
impedances connections are required. Newer Counter/Working cables use a simple design with fuses located
within the cable hood. This approach is less expensive and allows for lower inductance cell connections
NOTE
Always turn off the Reference 3000 and disconnect both ends of the Counter/Working
cable before checking or replacing the fuses in the cable.
Access to the fuses requires removal of two screws located on opposite sides of the hood covering the
D-connector end of the Counter/Working cable. A drawing of the D-connector end of a cable with the hood
opened is seen in Figure 5-2. The small rectangular fuses snap into fuse-holders labeled Work and Cntr. To
remove the fuse, either grip it with small pliers and gently lift the fuse out of the fuse-holder, or pry the fuse out
of the fuse-holder using a small screwdriver or knife blade.
5-6
Chapter 5 -- Cell Connections--Fuses in the Cell Cable
Once a fuse has been removed, it can be checked using an ohmmeter, such as that found on modern digital
voltmeters. A blown (open) fuse should always have a resistance of greater than 100 Ohms. The resistance of a
good fuse is very small.
Don’t forget the jackscrews when you reassemble the hood.
Figure 5-2
Drawing of Fuse-holder in the D-Connector Hood
Four replacement fuses should accompany every Counter/Working cell cable shipped by Gamry Instruments.
The Gamry Part Number for the small rectangular fuses is 630-00021. If you need to source replacement fuses
locally, we currently only recommend Very Fast Acting, 3.15 amp, Nano Fuses from the Littelfuse corporation.
The Littelfuse Part Number is 04513.15MRL. Fuses with similar ratings from other manufacturers have not
been tested, so we cannot recommend their use.
CAUTION
Always replace the fuses in a Reference 3000 cable with the recommended
fuse. Use of improper fuse, especially a fuse with a higher current rating,
could cause instrument failure if a battery cell is improperly connected. Use
of a non-approved fuse will void Gamry’s factory warranty.
5-7
Chapter 5 -- Cell Connections--Fuses in the Cell Cable
Testing For Open Fuses
A Gamry Framework test checks for blown fuses without having you remove the fuses. A simple Potentiostatic
test is run on the Calibration Cell on the Gamry UDC4 Dummy Cell. The test is run using the “Set a
Voltage.exp” script in the Framework’s Utilities Package. Utility Package scripts do not require a Authorization
Code, so every Framework installation can run this test.
Connect the cell leads to the Calibration side of the UDC4. You do not need to place the UDC4 within a
Faraday cage. Select the command Experiment, Utilities, Set a Voltage on the Framework’s menu bar. You
will see a dialog box similar to this:
Figure 5-3
Setup Dialog Box for the “Set a Voltage” Script
Enter a Voltage of 1 volt as shown above, then press Ok. The Framework will open a Runner window and a
graph of current versus time should appear.
5-8
Chapter 5 -- Cell Connections--Fuses in the Cell Cable
Figure 5-4
Typical Runner Window with Good Fuses
We expect you will see one of two very different results:
•
If the instrument is working properly and the fuses in the cable are good, the measured current will be
around 500 µA as seen above. No overloads are seen.
•
If the one or both fuses are open, all the current readings will be near zero, and a red CA Overload
indication may be seen at the bottom of the runner window.
If this test indicates an open fuse, use the procedures described above to check both fuses. This test cannot tell
which fuse is blown. Both fuses can blow at the same time.
If the fuse test indicates an open fuse, and the fuses both check out a good with an ohmmeter, some other
problem has occurred in the cables or the instrument. Contact Technical Support at Gamry Instruments at your
earliest convenience.
5-9
Chapter 6 -- Panel Indicators and Connectors--Front Panel
Chapter 6 -- Panel Indicators and Connectors
Front Panel
The Reference 3000 front panel includes two connectors and four backlighted LED indicators. Each of these
will be discussed in turn. A picture of the Reference 3000 front panel can be seen in Figure 4 - 1.
The cell connections are discussed at great length in Chapter 5. A pin-out of the two cell cable connectors can
be found in Appendix B.
Counter/Working Connector
The Counter/Working connector is a 15-pin female D-type connector. It contains the high current connections
between a Reference 3000 and an electrochemical test cell.
The Counter/Working connector is normally connected to a Gamry Instruments supplied cell cable. Gamry’s
Counter/Working cables always include fuses that prevent instrument failure when a battery of other energy
source is improperly connected to the cable.
In addition to the pins used for cell connections, the Reference 3000 Counter/Working Connector also uses
five pins to read a cell cable ID. Gamry’s software can compensate for the cell cable characteristics for optimal
system performance, especially in EIS (Electrochemical Impedance Spectroscopy).
Sense Inputs Connector
The Sense Inputs connector is a 15-pin male D-type connector. It contains high impedance voltage sense
inputs. These inputs are used to measure voltages in the electrochemical test cell.
The Sense Inputs connector is normally connected to a Gamry Instruments supplied cell cable.
In addition to the pins used for cell connections, the Reference 3000 Sense Inputs connector also uses five pins
to read a cell cable ID. Gamry’s software can compensate for the cell cable characteristics for optimal system
performance, especially in EIS (Electrochemical Impedance Spectroscopy).
The Power LED
The Power LED is located on the lower left of the Reference 3000 front panel. It normally glows a steady blue,
when the Reference 3000 is turned on and has passed some simple self-tests.
When the Reference 3000 is first turned on, the Power LED will glow steadily for a second or two, blink three
times, and then go to its normal steady blue output. Each blink in this sequence indicates successful
completion of a portion of the Power PC’s power-up self-test routine.
A Reference 3000's Power LED blinks when that instrument is selected in the Framework's Instrument Manager.
This allows easy identification of a specific instrument in a MultEchem system without looking at the instrument
Serial Label on the bottom of the instrument chassis.
When the Power LED is off, either:
•
•
•
•
The rear panel power switch is off.
There is no DC +24 volt supply connected to the rear panel DC Power In connector.
The external DC power supply has no input power or is malfunctioning.
One part of the Power PC’s power-up self-test has failed.
6-1
Chapter 6 -- Panel Indicators and Connectors--Front Panel
CAUTION
The Power LED is used both to indicate power status and to indicate that power-up
tests have passed. It therefore cannot be relied on as a true power status indicator.
Always unplug the DC Power In connection if you suspect your Reference 3000 is
malfunctioning.
The USB LED
The USB LED is located just above the Power LED. It is a tri-color LED, capable of glowing green, orange, or
red.
The USB LED will be unlighted when:
•
•
•
•
•
The Reference 3000 is not powered.
The Reference 3000 does not have a USB cable plugged into its rear panel USB port.
The computer end of the USB cable is not plugged into a USB port on a computer or hub.
The USB cable is not supplying USB power to the Reference 3000.
The computer has disabled the USB port going to the Reference 3000.
The USB LED will glow a steady green if a valid USB connection has been made and the Reference 3000’s
communication processor is receiving power down the USB cable.
The USB LED will flash orange whenever the Reference 3000 is receiving or transmitting valid USB messages to
or from the host computer. It will not flash if there is USB traffic addressed to other devices on the USB bus,
including messages aimed at a different Reference 3000.
The USB LED will indicate a solid RED in one special condition. It will be red when a firmware download is
taking place. Interrupting a firmware download can cause a catastrophic failure of your system. Do not turn off
the Reference 3000, do not unplug the USB cable, and do not stop the host computer operation when the USB
LED is a steady red color.
CAUTION
Do not interrupt a firmware download while it is in progress. An incomplete
download can render a Reference 3000 inoperable until it is returned to Gamry for
reprogramming.
Cell LED
The Cell LED glows yellow whenever the Reference 3000 is actively applying voltage or current to the
electrochemical cell attached to the Cell Cable. You should avoid touching the cell cable leads whenever the
Cell LED is lighted, because the quality of the data being collected in your experiment may be compromised.
CAUTION
The Cell LED does not indicate a dangerous condition when it is lighted. The voltages
output by the Reference 3000 are generally considered to be safe. Still, you should
avoid touching the cell leads when the cell is on.
If you need to make changes to your cell leads, you normally do so between experiments, when the Cell LED is
off and the potentiostat is inactive.
In a typical experimental sequence, the Cell LED will be off between experiments and during any open circuit
potential measurements. It will glow yellow whenever the cell is polarized.
6-2
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
Overload LED
The Overload LED is normally unlighted. When it glows red, this indicates that some circuit in the Reference
3000 has exceeded its normal operating limit. Conditions that generate Overloads include:
•
The absolute value of the differential electrometer output voltage (the difference in voltage between
the Working and Reference leads) exceeds 10 volts. This condition is known as an E Overload.
•
The control amplifier has lost control of the cell.
Remember that the Reference 3000 can be operating with compliance limits of ± 1.5 Amps at ± 30
Volts or with compliance limits of ± 3.0 Amps at ± 15 Volts.
The absolute value of the cell current may be trying to exceed the compliance current or the absolute
value of the counter electrode voltage may be trying to exceed the compliance voltage setting. Either
condition will be called a Control Overload.
•
The absolute value of the cell current has exceeded full scale on the current range presently in use.
This condition is known as an I Overload.
An Overload indication does not indicate an instrument failure or system malfunction. Many normal conditions
can light the Overload indicator.
For example, transient (temporary) overloads during an experiment in which the cell voltage or current is being
stepped or swept are often normal. Consider the case of an infinitely fast voltage step into a perfect capacitor.
In theory, charging the capacitor requires an infinite current. The current spike seen at each step in a stepped
voltage waveform can easily light the Overload LED. The current spike will normally decay to near zero before
the actual current and voltage readings are taken.
Overload indications when the cell is being connected or disconnected are also common and usually do not
indicate a problem. Overloads can also be seen when one of the cell leads is disconnected from the other cell
leads, even though the cell is off. Again, this does not indicate a problem.
A steadily glowing Overload LED during an experiment most likely indicates a problem is occurring. Possible
causes include:
•
•
•
One of the cell leads is disconnected (this is the most common cause),
a gas bubble in the cell is blocking one of the electrodes,
the potentiostat could be oscillating (see the next chapter).
NOTE
As described above, a glowing red Overload LED does not necessarily indicate a system
malfunction. The Overload LED can light when one or more cell leads are disconnected,
without indicating a problem with the system. The Overload LED can often light
momentarily during a swept or stepped experiment. The only Overload LED indication
that definitely points towards a problem is a continuously glowing Overload LED during
an experiment.
Rear Panel
The rear panel contains one switch and a large number of connectors. A picture of the Reference 3000 rear
panel can be seen in Figure 4 - 2.
Power In Jack
The Reference 3000 derives all its power from a +24 volts DC supply connected to the Power In jack on the
lower right side of the rear panel. The input current is less than 5 amps.
6-3
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
We recommend that you always use the power adapter (power brick) supplied with your Reference 3000 to
power to the instrument.
Input power from the power adapter comes from your AC power main. The power adapter supply is rated for
operation from 100 to 240 volts AC, at frequencies from 47 to 63 Hz. It should therefore be useable
worldwide.
CAUTION
If your facility owns both Gamry Reference 600’s and Reference 3000’s, you must
insure that the smaller power adapter from the Reference 600 is not used to power a
Reference 3000. The Reference 3000 will not power up with the smaller adapter.
Fortunately, neither the Reference 3000 nor the small power adapter will be damaged
if connected in error.
The power adapter for the Reference 3000 is almost 22 cm long. The largest
dimension on the Reference 600 power adapter is 11 cm.
While a Reference 3000 may work with other power sources, we cannot guarantee it will work to its full
specifications. If you have to use the Reference 3000 with a different supply, make sure that the supply is
regulated, has an output between 22 and 26 volts, and supplies at least 5 amps of load current. Inrush current
drawn by the Reference 3000 at “power on” has been known to cause improper operation of an external
power supply, even though the supply is rated for more than 5 amps of output current.
WARNING
Power input voltages less than 20 volts or greater than 32 volts can damage the
Reference 3000’s DC-DC power supply.
Power Switch
The Power switch is located just below the Power In jack. It switches the power from this jack to the input of
the Reference 3000’s DC-DC converter.
Normally, the DC Power is connected before the Power Switch is turned ON. However, no damage will occur
if this switch is already in the ON position when the DC Power is connected, or when the AC power input is
connected to the external power supply.
Chassis Ground
The rear panel Chassis Ground is intended for one use only. When the Reference 3000 is used with cells
isolated from earth ground, connecting the chassis ground to earth ground may lower the noise measured in the
system. Note that the chassis of the Reference 3000 is connected to Floating Ground. See Chapter 1, for safety
information concerning this connection.
Either a banana plug or the stripped end of a wire can be connected to the Chassis Ground binding post. The
other end of the wire is then connected to earth ground.
A black banana-plug to banana-plug lead has been provided with your Reference 3000. You may find it useful
when making this earth ground connection.
USB Port
The USB port on the rear panel of the Reference 3000 is a Type B connector as defined in Revision 1.1 and 2.0
of the USB Specification. You use a standard, shielded, Type A/B cable to connect this port to a computer’s
USB port or a USB hub (preferably an externally powered hub). The two ends of a Type A/B cable are
6-4
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
different. The more-rectangular end plugs into the computer and the more-square end plugs into the Reference
3000.
A suitable USB cable was included with your Reference 3000 shipment. If this cable is lost, you can replace it
with a cable from your local computer retailer.
The Reference 3000 is a High Speed USB 2.0 peripheral, capable of data transfer at 480 Mbits/second. If it is
plugged into a computer port incapable of High Speed operation it will downgrade to USB 1.1 full speed
operation (12 Mbits/second). Obviously data transfer speed will be slower if this occurs.
The Reference 3000 USB port is compatible with Revision 1.1 and 2.0 of the USB specification. It supports the
Windows Plug-n-Play mechanism, including dynamic connect/reconnect.
The front panel USB LED should be green whenever a valid computer to Reference 3000 connection has been
made and both the computer and Reference 3000 are fully powered.
Thermocouple Input
The Reference 3000 has an input jack for a K Type thermocouple. The ISO standard calls for color-coded
mini-thermocouple connections. Yellow is the color assigned to K Type thermocouples. The mating connector
on your thermocouple should therefore be yellow.
Possible uses for temperature measurement in an electrochemical test include:
•
Looking for a temperature rise at end-of-charge on a battery.
•
Measuring ambient temperature prior to a corrosion measurement.
•
Measuring temperature in a cell before making a CV measurement that will be used to calculate
reaction kinetics.
Gamry Instruments chose not to provide a thermocouple with the Reference 3000. There is simply too much
variety in the mechanical design of thermocouple probes. Commercial thermocouples designed for
measurement in air, on solid surfaces, and in immersion service are available from a variety of vendors. Make
sure you get a K type thermocouple.
The Reference 3000 uses a temperature measurement IC to convert the thermocouple output to a useable
voltage. It outputs a voltage that is nominally 10 mV per degree Celsius. The IC used, the Analog Device
AD594A, is rated for an accuracy of 3°C. Even this accuracy is only achieved when the Reference 3000 is
calibrated. The scaling at the A/D converter is ± 3 volts full scale, or ± 300°C full scale.
The Reference 3000 calibration script has an optional section for thermocouple calibration. An ice-water bath
and a beaker of boiling water provide convenient standards for a two-point calibration.
CAUTION
One side of the thermocouple is connected to the Reference 3000’s Floating Ground.
An improper connection to the thermocouple input can compromise the Reference
3000’s ability to float and invalidate data collected on earth grounded cells. A
connection to an non-insulated thermocouple immersed in your electrochemical cell
can also cause erroneous readings.
Misc I/O Connector
The Misc (Miscellaneous) I/O connector is a multipurpose connector. It contains both digital and analog signals
used to interface external devices to the Reference 3000.
All of its signals are isolated from both earth ground and the Reference 3000’s Floating Ground. The device
connected to this connector establishes a ground reference. This isolation allows the Misc I/O connector to be
connected to earth grounded apparatus, without compromising the Reference 3000’s ground isolation.
6-5
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
A full description of this connector can be found in Appendix C of this manual. This appendix includes details
such as connector pin-out, output and input voltage levels and full signal descriptions.
The following list is a short description of the signals in the Misc I/O Connector and their uses:
•
•
•
•
•
•
Sync Out and Sync In signal allow two or more Reference 3000s to use one data acquisition clock.
Four digital outputs can be used to turn on external devices under control of an Explain experimental
control script.
Some of Gamry applications assign three of the digital output to control stirring, flow of deaeration gas,
and formation of mercury drops on a mercury drop electrode.
Four digital inputs that can be read in an Explain experimental control script.
A 12-bit D/A converter used to set “continuously variable” settings, such as electrode rotation rate on a
rotating disk electrode.
A 5 volt isolated power supply that can provide up to 50 mA of current for external circuitry.
Caution
Floating operation of Reference 3000 can be compromised by improper cabling to the
User I/O Connector. We do not recommend use of standard 15-pin shielded cables with
this connector. Custom cables with the shield connected to pin 6 of the D-connector are
preferred.
I Monitor BNC
The I Monitor BNC connector represents the output of the Reference 3000’s current measurement circuit.
With the exception of the filtering described below, it is the raw signal. It will be high bandwidth on the less
sensitive current ranges. The effective bandwidth of the current signal falls as you reach the nA and pA current
ranges. IE Stability capacitors further slow the response.
The outer shell of this BNC connector is connected to the Reference 3000’s floating ground.
CAUTION
The shell of the I Monitor BNC is connected to the Reference 3000’s Floating Ground.
Connection of this BNC to earth ground referenced equipment can compromise the
Reference 3000’s ability to float and invalidate data collected on earth grounded cells.
Scaling on this signal is ±3 volts for ± the nominal full scale current on the selected current range. Cathodic
currents will cause a positive output voltage. If the software is auto-ranging the current-range selection, this
signal will be discontinuous at each range change.
The I Monitor BNC connector is lightly filtered using an RLC circuit. It has a bandwidth of approximately
3 MHz when connected to a high impedance input. This bandwidth will be further reduced if a coaxial cable is
connected to the BNC. Its output impedance is approximately 200 Ohms in parallel with 220 pF.
E Monitor BNC
The E Monitor BNC connector is the output of the Reference 3000’s differential electrometer circuit. With the
exception of the filtering described below, it is a buffered representation of the voltage difference between the
white and blue cell cable leads. It has a high bandwidth.
The outer shell of the BNC connector is connected to the Reference 3000’s floating ground.
6-6
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
CAUTION
The shell of the E Monitor BNC is connected to the Reference 3000’s Floating Ground.
Connection of this BNC to earth ground referenced equipment can compromise the
Reference 3000’s ability to float and invalidate data collected on earth grounded cells.
The E Monitor BNC connector is lightly filtered using an RLC circuit. It has a bandwidth of approximately
3 MHz when connected to a high impedance input. This bandwidth will be further reduced if a coaxial cable is
connected to the BNC. Its output impedance is approximately 200 Ohms in parallel with 220 pF.
Ext. Sig. In BNC
The External Signal In BNC connector allows you to add a voltage to the Reverence 600’s Signal Generator.
This signal will be summed with the other signal generator sources including the IR DAC, the Scan DAC, and
the DDS output.
The outer shell of the BNC is connected to the Reference 3000’s floating ground.
CAUTION
The shell of the Ext Sig In BNC is connected to the Reference 3000’s Floating Ground.
Connection of this BNC to earth ground referenced equipment can compromise the
Reference 3000’s ability to float and invalidate data collected on earth grounded cells.
The signal generator output is usually directly connected to the potentiostat’s input. When the cell is turned on
in potentiostat mode, the feedback is such that a negative signal generator output creates a positive differential
electrometer signal, which corresponds to a negative working electrode versus reference electrode voltage.
The polarity of the External Signal In signal is inverted at the signal generator’s output. As described above, a
negative input signal on this BNC will create a positive change in the working electrode versus reference
electrode voltage. The input impedance of this signal is 3 kΩ in parallel with 15 pF.
Sig Gen Out BNC
The Sig Gen Out BNC connector allows you to monitor the “signal generator” signal being sent from the
Reference 3000’s controller board to the potentiostat board. This signal has a high bandwidth. The signal
output range is –15 volts to +15 volts.
The outer shell of the BNC is connected to the Reference 3000’s floating ground.
CAUTION
The shell of the Ext Sig In BNC is connected to the Reference 3000’s Floating Ground.
Connection of this BNC to earth ground referenced equipment can compromise the
Reference 3000’s ability to float and invalidate data collected on earth grounded cells.
The Sig Gen Out BNC connector is lightly filtered using an RLC circuit. It has a bandwidth of approximately
3 MHz when connected to a high impedance input. This bandwidth will be further reduced if a coaxial cable is
connected to the BNC. Its output impedance is approximately 200 Ohms in parallel with 220 pF.
Aux In BNC
The Aux In BNC connector allows you to measure a voltage from outside the Reference 3000 using the
Reference 3000’s internal A/D. The scaling is: ±3 volts in equals ±30000 A/D counts. This is a resolution of
100 µV per bit. The results will be reported in volts. The input is differential (see Appendix D).
The allowed input voltage range is ±5 volts. Input voltages outside this range could result in damage the
Reference 3000.
Consult Appendix D for additional information concerning this connector.
6-7
Chapter 6 -- Panel Indicators and Connectors--Rear Panel
Expansion Interface
The expansion interface is a D-connector on the Reference 3000 reserved for use with the Gamry Reference
30k Booster to provide additional cell current up to 30Amps. A specially designed digital cable connects the
Expansion Interface port to the booster. Consult the Reference 30k Booster manual for the details of setting up
a booster.
6-8
Chapter 7 -- Auxiliary Electrometer Option--Overview
Chapter 7 -- Auxiliary Electrometer Option
Overview
The AE is a factory-installed option for the Reference 3000. The AE acronym stands for Auxiliary Electrometer.
The AE allows eight independent, high voltage differential electrometer channels available to be read by the
Reference 3000’s A/D converter. Difference voltages (between the two inputs of each channel) of up to ± 5 V
can be measured.
All AE inputs are rated to operate at all voltages available at the Reference 3000’s Counter Electrode terminal.
This allows operation between –18 volts and +18 volts in the 3 amp/15 volt compliance setting and between
-36 volts and +36 volts in the 1.5 amp/30 volt compliance setting. These voltages are all versus the Reference
3000’s Floating Ground.
The channels are all completely independent. One channel can measure the difference between -1 V and
-2 V while a different channel measures the difference between 30V and 31V.
The primary function of the AE is simultaneous measurement of individual cells within a multi-cell battery, fuel
cell, or super-capacitor stack. Both AC parameters and DC performance of the cells can be measured. The
stack is often polarized using Galvanostatic control. Alternatively, you can use the Reference 3000 in Stack
mode to control the voltage of the entire stack or of one cell in the stack.
Regardless of the control mode used, the same cell current flows though all the cells in the stack. As a result,
we only need voltage measurements to measure the current and voltage of each cell in the stack. You can also
use the AE to use to measure non-electrochemical signals. The voltage input to an AE channel can be the
output from a temperature, pressure, or other transducer.
AC Performance and CMRR
Each AE channel has 2 differential inputs. The channel measures the difference voltage between these inputs,
labeled as the + input and the - input.
The AE inputs can operate with input voltages as high as 36 volts and can still maintain pA level input currents.
They are also capable of high-speed measurements. The AE is specified to have less than 2° of phase shift for
100 kHz input signals applied to an input channel.
Another very important, although often disregarded, specification for differential inputs is common mode
rejection (CMR). CMR is a measure of how well differential inputs reject a signal applied equally to both inputs
(often called a common mode input). The ratio of output voltage to common mode voltage is called the
common mode rejection ratio, CMRR. By convention, it has units of dB, a logarithmic scale where 20 dB
represents a factor of 10. Assuming one volt of common mode voltage, 20 dB of CMRR corresponds to 100
mV of output voltage, 40 dB corresponds to 10 mV, 60 dB corresponds to 1 mV, etc.
CMR is generally dependent on frequency. As frequency increases, CMRR falls. Each AE channel is specified
to have better than 94 dB CMRR at frequencies between DC and 5 kHz and better than 76 dB of CMRR
between 5 kHz and 100 kHz.
NOTE
AC CMR is highly dependant on resistance in the measurement leads. The AE’s CMR
specifications only apply when the there is less than 10 Ω of resistance in the input leads.
A typical aqueous reference electrode has 500 Ω of resistance. Gamry does not
recommend use of reference electrodes in high frequency AE measurements.
7-1
Chapter 7 -- Auxiliary Electrometer Option--Experiments
CMR is especially important when the AE is used to measure the voltage of individual cells in a battery or fuelcell stack. Cells near the Working Electrode have relatively low DC voltages, since the working electrode
voltage is near ground. Cells near the Counter electrode have higher DC voltages. When an AC signal is
applied to the stack, the counter electrode end of the stack has higher AC voltages.
Let’s look at a hypothetical example. A battery stack has 22 cells, with an average DC cell voltage equal to 1.5
volts. The bottom cell in the battery stack is attached to the working electrode and the top cell is attached to
the counter electrode. A 100 kHz AC signal is applied, creating an average AC voltage of 10 mVrms per cell.
Assume the working electrode is at zero volts versus floating ground. The DC voltages on the top cell are 31.5
volts and 33 volts. This can also be described as 31 volts of common mode voltage plus a 1.5 volt differential
voltage. The AC voltages on the top cell are 210 mV of common mode voltage and 10 mV of differential
voltage.
Applying the 94 dB minimum low frequency CMRR spec, we can calculate the DC error in the voltage due to
the DC common mode voltage.
Maximum DC Error = Vcm / CMRR = 31 V / 94 dB = 31 V/ 50,000 = 620 µV.
This is quite small compared to the 1.5 volt cell voltage, so it can be ignored.
At 100 kHz, the CMRR is specified to be at least 74 dB.
Maximum AC error = Vcm / CMRR = 0.21 V / 74 dB = 0.21 V/ 5,000 = 42 µV.
If this AC error is 90° out of phase with the true AC voltage on the cell, it creates a phase error of 0.2° in the
measured AC voltage. This is not significant, since the AC accuracy specification at 100 kHz is ± 2°.
Experiments
The AE option is supported only by the Galvanostatic EIS, Galvanostatic Single Frequency EIS, and Hybrid EIS
Framework scripts, as well as the experiments performed through Gamry PWR800 Software.
Connections Using Standard Cables
The AE connects to an electrochemical cell using one, two, three or four cables. Other than labeling, all four
cables are identical. Each cable supports two AE channels.
NOTE
The cables are interchangeable, but we do not recommend using a numbered cable in a
differently numbered connector. The connections get much too confusing.
Table 7-1 shows the pin-out of these cables.
7-2
Chapter 7 -- Auxiliary Electrometer Option--Connections Using Custom Cables
Table 7-1
AE Cable Connections
Pin
Type
Name
Wire Color
Connector
Color
Normal Connection
1
Analog Input
Odd Ch -
Black
Yellow
Low side of odd channel
reference side
2
Analog Input
Odd Ch +
Black
Purple
High side of odd channel
working side
3
Ground
Floating Ground
--
--
4
Analog Input
Even Ch -
Red
Yellow
Low side of even channel
reference side
5
Analog Input
Even Ch +
Red
Purple
High side of even channel
working side
6
Ground
Floating Ground
--
--
7
Digital input
!Cable
Ground if cable present
8
Digital In
!Power On
Ground if AE powered
9
Ground
Floating Ground
Note that pins 8 and 9 must be grounded on any cable that will be used to take voltage readings.
The analog inputs are both labeled (with labels on the wires) and color coded. The wires are black for odd
numbered channels (Channel 1,3, 5, and 7) and red for the even numbered channels (Channels 2, 4 ,6 and 8).
The working side plug (the positive input) is purple, and the reference side (the negative input) is yellow.
Connections Using Custom Cables
The user can build custom cables for AE connections. Follow the pin designations in the table above. Pins 7
and 8 must be grounded.
AE Specifications
See Appendix E.
7-3
Chapter 8 -- Stability in Potentiostat Mode--Capacitive Cells and Stability
Chapter 8 -- Stability in Potentiostat Mode
Capacitive Cells and Stability
All potentiostats can become unstable when connected to capacitive cells. The capacitive cell adds phase shift
to the potentiostat's feedback signal (which is already phase shifted). The additional phase shift can convert the
potentiostat's power amplifier into a power oscillator.
To make matters worse, almost all electrochemical cells are capacitive because an electrical double layer forms
next to a conductor immersed in a solution.
Potentiostat oscillation is an AC phenomenon. However, it can affect both AC and DC measurements.
Oscillation often causes excessive noise or sharp DC shifts in the system's graphical output. The Reference
3000 Potentiostat can be stable on less sensitive current ranges and unstable on more sensitive current ranges.
Whenever you see sharp breaks in the current recorded on the system, you should suspect oscillation.
The Reference 3000 has been tested for stability with cell capacitors between 10 pF and 0.1 F. In all but its
fastest control amp speed setting, it is stable on any capacitor in this range -- as long as the impedance in the
reference electrode lead does not exceed 20 kΩ. With reference electrode impedances greater than 20 kΩ,
the Reference 3000 may oscillate. The RC filter formed by the reference electrode impedance and the
reference terminal's input capacitance filters out the high frequency feedback needed for potentiostat stability.
Longer cell cables make the problem worse by increasing the reference terminal's effective input capacitance.
Even when the system is stable (not oscillating), it may exhibit ringing whenever there is a voltage step applied
to the cell. The Reference 3000's D/A converters routinely apply steps, even when making a pseudo-linear
ramp. While this ringing is not a problem with slow DC measurements, it can interfere with faster
measurements. The steps taken to eliminate potentiostat oscillation also help to minimize ringing.
8-1
Chapter 8 -- Stability in Potentiostat Mode--Improving Potentiostat Stability
Improving Potentiostat Stability
There are a number of things that you can do to improve an unstable or marginally stable Reference 3000
potentiostat/cell system. This list is not in any particular order. Any or all of these steps may help.
•
Slow down the potentiostat. The Reference 3000 has five control amplifier speed settings, which can
be selected in software. Slower settings are generally more stable.
•
Increase the Reference 3000's I/E stability setting. The Reference 3000 includes three capacitors that
can be paralleled with its I/E converter resistors. These capacitors are connected to relays that are
under software control. Contact your local Gamry Instruments' representative for more information
concerning changes in these settings.
•
Lower the reference electrode impedance. Make sure that you don't have a clogged reference
electrode junction. Avoid asbestos fiber reference electrodes and double-junction electrodes. Avoid
small diameter Luggin capillaries. If you do have a Luggin capillary, make sure that the capillary’s
contents are as conductive as possible.
•
Add a capacitively coupled low impedance reference element in parallel with your existing reference
electrode. The classic fast combination reference electrode is a platinum wire and a junction isolated
SCE. See Figure 8-1. The capacitor insures that DC potential comes from the SCE and AC potential
from the platinum wire. The capacitor value is generally determined by trial and error.
Figure 8-1
Fast Combination Reference Electrode
White
Cell Lead
100 pF to 10 nF
SCE
Platinum
Electrolyte
8-2
Chapter 8 -- Stability in Potentiostat Mode--Improving Potentiostat Stability
•
Provide a high frequency shunt around the cell. A small capacitor between the red and white cell
leads allows high frequency feedback to bypass the cell. See Figure 8-2. The capacitor value is
generally determined by trial and error. Ten nF (10000 pF) is a good starting point.
In a sense, this is another form of an AC coupled low impedance reference electrode. The counter
electrode is the low impedance electrode, eliminating the need for an additional electrode in the
solution.
Figure 8-2
High Frequency Shunt
Red
100 pF to 10 nF
White
Reference
Green
Working
8-3
Counter
Chapter 8 -- Stability in Potentiostat Mode--Improving Potentiostat Stability
•
Add resistance to the counter electrode lead. See Figure 8-3. This change lowers the effective
bandwidth of the control amplifier. As a rule of thumb, the resistor should be selected to give one
volt of drop at the highest current expected in the test being run. For example, if you expect your
highest current to be around 1 mA, you can add a 1 kΩ resistor.
This resistor has little or no effect on the DC accuracy of the potentiostat. It can create problems
in high-speed experiments such as fast CV scans or EIS, which need high bandwidth.
Figure 8-3
Resistor Added for Stability
Red
Resistor
White
Reference
Green
Working
8-4
Counter
Chapter 9 -- Measurement of Small Current Signals--Overview
Chapter 9 -- Measurement of Small Current Signals
Overview
The Gamry Instruments Reference 3000 is a high performance measurement instrument used for all types of
electrochemical testing. Unlike many other electrochemical instruments, it offers outstanding performance for
both tests with small current signals and high impedances and for tests involving large currents and very small
impedances.
Chapter 10 is a discussion of the latter problem, when currents are large, voltages and cell impedances are
small, and inductance limits measurements. These measurements include those encountered in research on:
•
•
•
Batteries
Fuel cells
Super-capacitors
Problems in the measurement of very small currents are discussed here. Examples of this type of testing
include:
•
Cells for testing painted metal samples
•
Cells for testing corrosion of bare metals
•
Microelectrode cells
•
Most cells for fast CV (cyclic Voltammetry)
•
Super-capacitors
Problem Description
The Reference 3000 is a very sensitive scientific instrument. It can theoretically resolve current changes as small
as 100 femoamp (1 x 10-13 amps). To place this current in perspective, 100 fA represents the flow of about
600,000 electrons per second!
The small currents measured by the Reference 3000 place demands on the instrument, the cell, the cables and
the experimenter. Many of the techniques used in higher current electrochemistry must be modified when
used to measure pA currents. In many cases, the basic physics of the measurement must be considered.
This chapter will discuss the limiting factors controlling low current measurements. It will include hints on cell
and system design. The emphasis will be on EIS (Electrochemical Impedance Spectroscopy), a highly
demanding application for the Reference 3000.
Measurement System Model and Physical Limitations
To get a feel for the physical limits implied by very sensitive current measurements, consider the equivalent
circuit shown in Figure 9-1. We are attempting to measure the cell impedance given by Zcell.
This model is valid for analysis purposes even though the real Reference 3000 circuit topology differs
significantly.
9-1
Chapter 9 -- Measurement of Small Current Signals--Measurement System Model and Physical Limitations
In Figure 9-1:
Es
Zcell
Icell
Rm
Is an ideal signal source
Is the unknown cell impedance
Is the “real” cell current
Is the current measurement circuit's current measurement resistance
Rshunt
Cshunt
Cin
Rin
Iin
Is an unwanted resistance across the cell
Is an unwanted capacitance across the cell
Is the current measurement circuit's stray input capacitance
Is the current measurement circuit's stray input resistance
Is the measurement circuit's input current
In the ideal current measurement circuit Rin is infinite while Cin and Iin are zero. All of the cell current, Icell,
flows through Rm.
With an ideal cell and voltage source, Rshunt is infinite and Cshunt is zero. All the current flowing into the
current measurement circuit is due to Zcell.
The voltage developed across Rm is measured by the meter as Vm. Given the idealities discussed above, one
can use Kirchoff's and Ohms law to calculate Zcell:
Zcell = Es * Rm / Vm
Figure 9-1
Equivalent Measurement Circuit
R shunt
C shunt
Icell
Rm
R in
9-2
C in
Chapter 9 -- Measurement of Small Current Signals--Measurement System Model and Physical Limitations
Unfortunately technology limits high impedance measurements because:
•
Current measurement circuits always have non-zero input capacitance, i.e. Cin > 0.
•
Infinite Rin cannot be achieved with real circuits and materials.
•
Amplifiers used in the meter have input currents, i.e. Iin > 0.
•
The cell and the potentiostat create both a non-zero Cshunt and a finite Rshunt.
Additionally, basic physics limits high impedance measurements via Johnson noise, which is the inherent noise
in a resistance.
Johnson Noise in Zcell
Johnson noise across a resistor represents a fundamental physical limitation. Resistors, regardless of
composition, demonstrate a minimum noise for both current and voltage, per the following equations:
E = (4 k T R δF)1/2
I = (4 k T δF / R)1/2
Where;
k = Boltzman's constant 1.38x 10-23 J/oK
T = temperature in oK
δF = noise bandwidth in Hz
R = resistance in ohms.
For purposes of approximation, the Noise bandwidth, δF, is equal to the measurement frequency. Assume a
1011 ohm resistor as Zcell. At 300 oK and a measurement frequency of 1 Hz this gives a voltage noise of 41 µV
rms. The peak-to-peak noise is about 5 times the rms noise. Under these conditions, you can make a voltage
measurement of ± 10 mV across Zcell with an error of about ± 0.4%. Fortunately, an AC measurement can
reduce the bandwidth by integrating the measured value at the expense of additional measurement time. With
a noise bandwidth of 1 mHz, the voltage noise falls to about 1.3 µV rms.
Current noise on the same resistor under the same conditions is 0.41 fA. To place this number in perspective, a
± 10 mV signal across this same resistor will generate a current of ± 100 fA, or again an error of up to ± 0.4%.
Again, reducing the bandwidth helps. At a noise bandwidth of 1 mHz, the current noise falls to 0.013 fA.
With Es at 10 mV, an EIS system that measures 1011 ohms at 1 Hz is about 2 ½ decades away from the Johnson
noise limits. At 10 Hz, the system is close enough to the Johnson noise limits to make accurate measurements
impossible. Between these limits, readings get progressively less accurate as the frequency increases.
In practice, EIS measurements usually cannot be made at high enough frequencies that Johnson noise is the
dominant noise source. If Johnson noise is a problem, averaging reduces the noise bandwidth, thereby
reducing the noise at a cost of lengthening the experiment.
Finite Input Capacitance
Cin in Figure 9-1 represents unavoidable capacitances that always arise in real circuits. Cin shunts Rm, draining
off higher frequency signals, limiting the bandwidth that can be achieved for a given value of Rm. This
calculation shows at which frequencies the effect becomes significant. The frequency limit of a current
measurement (defined by the frequency where the phase error hits 45o) can be calculated from:
fRC = 1/ ( 2 π RmCin )
Decreasing Rm increases this frequency. However, large Rm values are desirable to minimize the effects of
voltage drift and voltage noise in the I/E converter’s amplifiers.
A reasonable value for Cin in a practical, computer controllable, low current measurement circuit is 20 pF. For
a 6 nA full scale current range, a practical estimate for Rm is 107 ohms.
9-3
Chapter 9 -- Measurement of Small Current Signals--Measurement System Model and Physical Limitations
fRC = 1/ 6.28 (1x107 )(2x10-12) ≈ 8000 Hz
In general, one should stay two decades below fRC to keep phase shift below one degree. The uncorrected
upper frequency limit on a 6 nA range is therefore around 80 Hz.
One can measure higher frequencies using the higher current ranges (i.e. lower impedance ranges) but this
would reduce the total available signal below the resolution limits of the "voltmeter". This then forms one basis
of statement that high frequency and high impedance measurements are mutually exclusive.
Software correction of the measured response can also be used to improve the useable bandwidth, but not by
more than an order of magnitude in frequency.
Leakage Currents and Input Impedance
In Figure 9-1, both Rin and Iin affect the accuracy of current measurements. The magnitude error due to Rin is
calculated by:
Error = 1- Rin/(Rm+Rin)
For an Rm of 107 ohms, an error < 1% demands that Rin must be greater than 109 ohms. PC board leakage,
relay leakage, and measurement device characteristics lower Rin below the desired value of infinity.
A similar problem is the finite input leakage current Iin into the voltage measuring circuit. It can be leakage
directly into the input of the voltage meter, or leakage from a voltage source (such as a power supply) through
an insulation resistance into the input. If an insulator connected to the input has a 1012 ohm resistance
between +15 volts and the input, the leakage current is 15 pA. Fortunately, most sources of leakage current
are DC and can be tuned out in impedance measurements. As a rule of thumb, the DC leakage should not
exceed the measured AC signal by more than a factor of 10.
The Reference 3000 uses an input amplifier with an input current of around 5 pA. Other circuit components
may also contribute leakage currents. You therefore cannot make absolute current measurements of very low
pA currents with the Reference 3000. In practice, the input current is approximately constant, so current
differences or AC current levels of less than one pA can usually be measured.
Voltage Noise and DC Measurements
Often the current signal measured by a potentiostat shows noise that is not the fault of the current
measurement circuits. This is especially true when you are making DC measurements. The cause of the
current noise is noise in the voltage applied to the cell.
Assume that you have a working electrode with a capacitance of 40 µF. This could represent a 1 cm2 polished
noble metal immersed in an electrolyte solution. You can roughly estimate the capacitance of the electrical
double layer formed by a metal/electrolyte interface as 20 µF/cm2. The area is the microscopic area of the
surface, which is larger than the geometric area, because even a polished surface is rough. The impedance of
this 40 µF electrode, assuming ideal capacitive behavior, is given by:
Z = 1/ωC
At sixty Hertz, the impedance magnitude is about 66 Ω.
Apply an ideal DC potential across this ideal capacitor and you get no DC current.
Unfortunately, all potentiostats have noise in the applied voltage. This noise comes from the instrument itself
and from external sources. In many cases, the predominant noise frequency is the AC power line frequency.
9-4
Chapter 9 -- Measurement of Small Current Signals--Hints for System and Cell Design
Assume a realistic noise voltage, Vn, of 10 µV (this is lower than the noise level of most commercial
potentiostats). Further, assume that this noise voltage is at the US power line frequency of 60 Hz. It will create
a current across the cell capacitance:
I = Vn/Z ≈ 10 x 10-6/ 66 ≈ 150 nA
This rather large noise current will prevent accurate DC current measurement in the low nA or pA ranges.
In an EIS measurement, you apply an AC excitation voltage that is much bigger than the typical noise voltage,
so this is not a factor.
Shunt Resistance and Capacitance
Non-ideal shunt resistance and capacitance arise in both the cell and the potentiostat. Both can cause
significant measurement errors.
Parallel metal surfaces form a capacitor. The capacitance rises as either metal area increases and as the
separation distance between the metals decreases.
Wire and electrode placement have a large effect on shunt capacitance. If the clip leads connecting to the
working and reference electrodes are close together, they can form a significant shunt capacitor. Values of 1 to
10 pF are common. This shunt capacitance cannot be distinguished from "real" capacitance in the cell. If you
are measuring a paint film with a 100 pF capacitance, 5 pF of shunt capacitance is a very significant error.
Shunt resistance in the cell arises because of imperfect insulators. No material is a perfect insulator (one with
infinite resistance). Even Teflon, which is one of the best insulators known, has a bulk resistivity of about 1012
ohms•m. Worse yet, surface contamination often lowers the effective resistivity of good insulators. Water films
can be a real problem, especially on glass.
Shunt capacitance and resistance also occur in the potentiostat itself. The Reference 3000 Potentiostat Mode
specifications in Appendix A contain equivalent values for the potentiostat's Rshunt and Cshunt. These values can
be measured by an impedance measurement with no cell.
In most cases, the cell's shunt resistance and capacitance errors are larger than those from the potentiostat.
Hints for System and Cell Design
The following hints may prove helpful.
Faraday Shield
A Faraday shield surrounding your cell is mandatory for very low-level measurements. It reduces both current
noise picked up directly on the working electrode and voltage noise picked up by the reference electrode.
A Faraday shield is a conductive enclosure that surrounds the cell. The shield can be constructed from sheet
metal, fine mesh wire screen, or even conductive paint on plastic. It must be continuous and completely
surround the cell. Don't forget the areas above and below the cell. All parts of the shield must be electrically
connected. You will need an opening in the shield large enough to allow a cell cable to enter the shield.
The shield must be electrically connected to the Reference 3000's floating ground terminal.
An additional connection of both the shield and the Reference 3000 floating ground to an earth ground may
also prove helpful.
9-5
Chapter 9 -- Measurement of Small Current Signals--Hints for System and Cell Design
NOTE
Only connect the Reference 3000 ground to earth ground if all conductive cell
components are well isolated from earth ground. A glass cell is usually well isolated. An
autoclave is generally not well isolated.
Avoid External Noise Sources
Try to keep your system away from electrical noise sources. Some of the worst are:
•
Fluorescent lights
•
Motors
•
Radio transmitters
•
Computers and computer monitors
Try to avoid AC powered or computerized apparatus within your Faraday shield.
Cell Cable Length and Construction
The Reference 3000 is shipped with 60 cm shielded cell cables. We also offer extended length cables and
unshielded cables as extra cost options.
Cell cables longer than 1 meter will result in degraded instrument performance. Increased noise and decreased
stability both can occur. However, with most cells, the instrument will work acceptably with an extended cell
cable, so our advice is go-ahead and try it. As a rule, you should not attempt to use current interrupt IR
compensation with cell cables longer than 5 meters.
We do not recommend that you use the Reference 3000 with any cables not supplied by Gamry Instruments.
The Reference 3000 cable is not a simple cable like a typical computer cable. The Reference 3000 cable
includes a number of individually shielded wires contained within an overall shield. The Counter/Working
cable contains fuses. We pay careful attention to issues such as shield isolation, isolation resistance, and
capacitance.
If you do need a special cable, contact us with your requirements.
Lead Placement
Many experiments with the Reference 3000 involve cells with small capacitances, the value of which may be
important.
In these cases, the capacitance between the Reference 3000's cell leads can result in an error. The Reference
3000 alligator clips can have 10 pF or more of mutual capacitance if they are run alongside each other.
If you wish to avoid excessive capacitance:
•
Place the leads as far apart as possible. Pay special attention to physical separation between the
working electrode/ working sense leads and the counter/ counter sense/ reference electrode leads.
•
Have the leads approach the cell from different directions.
•
Remove the alligator clips from the leads. In extreme cases you can replace the banana plugs and
pin jack with smaller connectors. If you do so, be careful not to compromise the isolation between
the center conductor and the shield.
The cell leads must not be moved during an experiment measuring small currents. Both microphonic and
triboelectric effects can create spurious results when the cell cables are moved.
9-6
Chapter 9 -- Measurement of Small Current Signals--Floating Operation
Cell Construction
If you need to measure small currents or high impedances, make sure that your cell construction does not limit
your response.
A cell where the resistance between the electrodes is only 1010 ohms cannot be used to measure 1013 ohm
impedances. In general, glass and Teflon are the preferred cell construction materials. Even glass may be a
problem when it is wet.
You also must worry about Cshunt. Make the "inactive" portion of your electrodes as small as possible. Avoid
placing electrodes close together or parallel with each other if you are measuring high impedances.
Reference Electrode
Keep your reference electrode impedance as low as possible. High impedance reference electrodes can cause
potentiostat instability and excessive voltage noise pickup.
Try to avoid:
•
Narrow bore or Vycor tipped Luggin capillaries.
•
Poorly conductive solutions - especially in Luggin capillaries.
•
Asbestos thread and double junction reference electrodes.
Reference electrodes often develop high impedances as they see use. Anything that can clog the isolation frit
can raise the electrode impedance. Avoid using saturated KCl based references in perchlorate ion solutions
Instrument Settings
There are several things to remember in setting up a very sensitive experiment.
•
In EIS, use the largest practical excitation. Don't use a 10 mV excitation on a coated specimen that
can handle 100 mV without damage.
•
Avoid potentials where large DC currents flow. You cannot measure 1pA of AC current on top of
1 mA of DC current.
EIS Speed
In EIS, do not expect the Reference 3000 to measure 1010 ohm impedances at 1 kHz. Many of the factors
listed above limit the performance.
As a rule of thumb, the product of Impedance, Z, times frequency, f, should be less than 109 ΩHz for good EIS
measurements with a Reference 3000.
Z · f < 109 ΩHz
Ancillary Apparatus
Do not use the Reference 3000 with ancillary apparatus connected directly to any of the cell leads. Ammeters
and voltmeters, regardless of their specifications, almost always create problems when connected to the
Reference 3000 cell leads.
Floating Operation
The Reference 3000 is capable of operation with cells where one of the electrodes or a cell surface is at earth
ground. Examples of earth grounded cells include: autoclaves, stress apparatus, pipelines, storage tanks and
battleships. The Reference 3000's internal ground is allowed to float with respect to earth ground when it works
with these cells, hence the name floating operation.
9-7
Chapter 9 -- Measurement of Small Current Signals--Floating Operation
Instrument performance can be substantially degraded when the Reference 3000 is operated in a floating
mode. The instrument specifications only apply on isolated cells with the Reference 3000 earth ground
referenced (not floating).
Special precautions must be taken with the cell connections when the Reference 3000 must float. Make sure
that all the cell connections are isolated from earth ground. In this case, you must disconnect the chassis
ground terminal of the Reference 3000 from earth ground.
Finally, ancillary apparatus connected to the Reference 3000 must be isolated. External voltmeters, ammeters,
FRA's etc. must be isolated. This includes devices connected to the monitor connectors located on the
Reference 3000 rear panel.
9-8
Chapter 10 – EIS Measurement of Small Impedances--Overview
Chapter 10 – EIS Measurement of Small Impedances
Overview
The Gamry Instruments Reference 3000 is a high performance measurement instrument used for all types of
electrochemical testing. Unlike many other electrochemical instruments, it offers outstanding performance for
both tests with small current signals and high impedances and for tests involving large currents and very small
impedances.
Problems in the measurement of very small currents were discussed in the previous chapter.
This chapter is a discussion of a very different type of problem, when currents are large, voltages and cell
impedances are small, and inductance limits measurements. These measurements include those encountered
in research on:
•
•
•
Batteries
Fuel cells
Super-capacitors
Results from fast transient techniques (CV, Chronopotentiometry, etc,) or high frequency EIS measurements on
low impedance systems are often limited by the cell cable and connections to the cell. An improper cell cable
or a proper cell cable badly connected can cause significant errors in the data obtained.
This chapter should answer these questions:
•
•
•
•
•
Why is Galvanostatic operation preferred when measuring Low Impedance?
What are the sources of error in measuring low impedance cells?
Why Use Four-terminal Measurement Techniques
What is mutual inductance?
How do I connect a cable to my cell to minimize errors?
Why Galvanostatic Mode?
Even though Potentiostatic EIS is the most commonly used EIS technique, it is poorly suited to impedance
measurements of low impedance batteries, fuel cells and super-capacitors.
This is why:
Current, voltage, and impedance are related through Ohm’s Law. Assume that a high-rate battery has an
impedance of 1 mΩ. A voltage of 1 mV across a 1 mΩ impedance leads to 1 A of current. No commercial
potentiostat is specified to control a cell’s potential (typically 0.5 V to 4.5 V) with less than 1 mV of absolute
error. When a potential with a 1 mV (or larger) error is applied to a low impedance battery or fuel cell a very
large DC current will flow. This current, given enough time, can alter a battery’s state-of-charge.
Conversely, a galvanostat can easily control ampere currents to an accuracy of a few milliamps. The voltage on
a battery or fuel cell is usually unaffected when the galvanostat is connected. The DC current is zero or some
user defined value.
A modern EIS system with AC coupling or offset and gain in the voltage measurement can measure microvolts
of AC voltage superimposed on a large DC voltage, as long as that DC voltage is stable.
10 - 1
Chapter 10 – EIS Measurement of Small Impedances--DC Errors and Four-terminal Measurements
DC Errors and Four-terminal Measurements
Four-terminal measurements are a common technique used in precision measurement of small impedances. In
a four-terminal measurement, a nominally two-terminal device, such as a resistor or a battery, is connected
using four leads. Two of the leads carry the current that must flow through the device to make the
measurement. The other leads measure the voltage created by that current.
An illustration of two-terminal measurements versus four-terminal measurements can be seen in Figure 10-1.
Both schematic diagrams show a resistance measurement made by passing a known current through an
unknown resistance, Rtest. The wires in the circuit have a resistance Rwire. A high input-impedance voltmeter
reads a voltage that is divided by the current value to calculate the value of Rtest.
In the two-terminal case, the voltage measurement is made using the same wires that carry the current. The
voltmeter measures:
V = Itest x ( 2 H Rwire + Rtest)
The calculated Rtest is too high, since the resistance of the wires is added to the unknown resistance.
In the four-terminal case, the voltmeter uses two additional wires to measure the voltage close to Rtest. The
current is carried through the original pair of wires. There is no current through the voltmeter wires, so the wire
resistance does not create voltage drop. The voltmeter measures:
V = Itest x Rtest
The addition of two wires to the circuit eliminates the error caused by the resistance of the wires.
Figure 10-1
Two and Four Terminal Measurements
10 - 2
Chapter 10 – EIS Measurement of Small Impedances--What is Mutual Inductance?
Four-terminal measurements are also useful in AC measurements, although there is a factor called mutual
inductance (discussed below) makes the AC case more complicated. Ignoring this complication for a moment,
a simple extension of the discussion above will show that four-terminal measurements can also eliminate the
effects of wire inductance.
In the real world, true four-terminal measurements are rarely possible. There is almost always some metallic
conductor shared by both current carrying leads and the voltage sensing leads. The metal volume shared
between the current carrying function and the sensing function can be minimized, but not eliminated.
What is Mutual Inductance?
Before we can define Mutual Inductance, we must define some terms. As discussed above, four leads connect
to the cell in an electrochemical system used to test small impedances. We will group them into two pairs.
One pair is the counter and working leads (red and green). They carry the cell current so we will call them the
current carrying leads.
The reference and working sense leads (white and blue) form the second pair. They measure the voltage across
two points in the cell. These leads will be called the sense leads.
A “mutual inductive” effect limits the ability of any system to measure small impedances at higher frequencies.
The term mutual inductance describes the influence of the magnetic field generated by the current carrying
leads on the sense leads.
In essence, the current carrying leads are the primary of a transformer and the sense leads are the secondary.
The AC current in the primary creates a magnetic field that then couples to the secondary, where it creates an
AC voltage.
You can minimize the unwanted effect in a number of ways:
•
•
•
•
Avoid higher frequencies
Minimize the net field generated by the current carrying leads.
Separate the current carrying leads from the sense leads.
Minimize pickup of the field in the sense leads.
Each of these ways will be discussed below.
Avoid high frequencies
Mutual inductance is an inductive effect. The voltage error is given by:
Vs = M di/dt
where Vs is the induced voltage on the secondary, M is the coupling constant (with units of Henries), and di/dt
is the rate of change in the primary current. M depends on the closeness of the coupling and can range from
zero up to the value of the primary inductance (the inductance in the current carrying leads).
Assuming a constant amplitude waveform in the primary, di/dt is proportional to frequency. There is always a
frequency below which the effect of mutual inductance errors is unimportant. Unfortunately, many
electrochemical systems need information at frequencies above this limit.
Minimize the Net Magnetic Field
A current passing through a wire creates a magnetic field. The field strength is proportional to the current.
Fortunately, passing the same current in opposite directions through adjacent wires tends to cancel the external
field. This also minimizes the net inductance in the wires. In all Gamry Instruments Reference 3000
Counter/Working cable, the current carrying leads are bound together.
10 - 3
Chapter 10 – EIS Measurement of Small Impedances--How Should You Hook Up Your Cell?
From your basic physics course, you may remember that the E B cross-product relationship for current
through a wire obeys the Right-Hand-Rule. If your thumb points in the direction of the current flow in a wire,
when you curl your fingers around the wire, the magnetic field curves around the wire in the same direction as
your fingers.
The current in the primary wires is flowing in opposite directions in the two wires, so your thumb points in
opposite directions for each wire, causing some cancellation of the fields. If the wires were in exactly the same
place, the cancellation would be perfect.
Since the wires cannot be in identically the same location, the cancellation is imperfect, and some net magnetic
field is always present. The more the wires are separated, the larger the net field.
The most common arrangement for inductance and field minimization is the twisted pair. Two insulated wires
are simply twisted together. A coaxial wire arrangement with current flowing in opposite directions in the
center conductor and the outer conductor is also effective.
Separate the pairs
If you place a magnetic field probe near a wire passing current, you will measure a field inversely proportional
to the square of the distance between the probe and the wire.
In an electrochemical system, the probe is our sense wiring. Separating the sense wires from the current
carrying wires can dramatically reduce the magnetic coupling, reducing errors in the EIS measurement.
The Reference 3000 has two cell cables, so that we can separate the current carrying wires from the sense
wires. The current carrying pair is in the Counter/Working Cable and the sense pair is in the Sense Cable.
Twist the Sense Wires
The concept of a magnetic loop probe is useful in understanding why twisted wire minimizes magnetic pickup.
A loop of wire in a changing magnetic field will see a loop voltage proportional to the area of the loop.
Twisting the sense wires together helps in two ways – even though twisting the wire forms loops. First, the
twisted wires are forced to lie close to each other, minimizing the loop areas. Secondly, adjacent loops pickup
opposite polarity voltages resulting in cancellation.
How Should You Hook Up Your Cell?
Always use four-terminal connections to the cell. Try to avoid conductors that are shared by both the current
carrying path and the voltage sensing bath.
If your experiments are in the region where mutual inductance may limit performance, keep the voltage sensing
leads in a twisted pair and the current carrying leads in a different twisted pair. Keep the pair of sensing wires
far away from the pair of current carrying wires. Try to arrange each pair so that they approach the cell from
opposite directions.
These recommendations are summarized in the Figure below.
10 - 4
Chapter 10 – EIS Measurement of Small Impedances--How Should You Hook Up Your Cell?
Figure 10-2
Wiring Recommendations
System
Maximize
Current Carrying Leads
i
Sense Leads
10 - 5
i
Cell
Minimize
Appendix A -- Reference 3000 Specifications--
Appendix A -- Reference 3000 Specifications
All specifications are at an ambient temperature of 25 °C, with the Reference 3000 powered using the power
adapter shipped with the unit, standard shielded 60 cm cell cables, and the cell enclosed in a Faraday shield.
All specifications are after software calibration.
A numbered note qualifies many of the specifications. Many of these notes describe the method used to
measure a specification. The notes are found at the end of this appendix.
All specifications are subject to change without notice.
Control Amplifier
High Voltage, Low Current Mode
Compliance Voltage
Min
Typ
Min
± 30
± 31.5
± 1500
volts
Note 1a
mA
Note 2
Min
Typ
Min
± 15
± 16.2
± 3000
volts
Note 1b
mA
Note 2
Unity Gain Bandwidth
Typ
1100, 330, 50, 5.0, 0.5
kHz
Notes 3, 4
Slew Rate
Typ
10, 3, 0.5, 0.06, 0.006
V/µsec
Notes 3,4
Max Input Voltage
Min
± 10
volts
Note 5
Input Current
Max
6
pA
Notes 6
Input Resistance
Differential (between inputs)
Common Mode (input to ground)
Input Capacitance
Differential (between inputs)
Common Mode (input to ground)
Bandwidth (-3 dB)
Typ
100
1
TΩ
Note 7
0.2
12
15
pf
Note 7
MHz
Note 8
CMMR
DC to 100 kHz
100 kHz to 1 MHz
Min
Output Current
Low Voltage, High Current Mode
Compliance Voltage
Output Current
Both Modes
Differential Electrometer
Typ
Min
80
60
Note 9
Voltage Measurement
A/D Full Scale Ranges
Typ
Resolution
Typ
400, 100, 10, 1
µV/bit
Zero Offset Error
Max
1
mV
Note 11
Gain Error
Max
0.2
%
Note 11
±12.0, ± 3.0, ± 0.3, ± 0.03
11 - 1
Volts
Note 3
Appendix A -- Reference 3000 Specifications--
Offset Range
Typ
± 10
Volts
Maximum Full Scale Range
3000
mA
Note 12
Minimum Full Scale Range
pA
pA
mV at
full scale
Volts
full scale
pA
Note 12
% of
range
% of
reading
Note 14
Current to Voltage Converter
Voltage across Rm
Typ
300
3 (after x100 gain)
150
Output Voltage (at BNC and ADC in)
Typ
3.0
Input Offset Current
Max
Typ
Max
5
2
0.05
Range Zero Offset
Gain Tolerance
3000 mA to 3 nA ranges
300 pA range
Zero drift
Max
Bandwidth
3000 mA to 300 µA ranges
30 µA range
3 µA range
Typ
Typ
0.2
0.5
0.03
MHz
Current Measurement
Typ
0.00333…
Offset Range
Typ
± 100
Post- Offset Gain
Typ
1x, 10x, 100x
Accuracy
Typ
Dominated by current to voltage error
(see above)
11 - 2
Note 14
Note 14
% FS /°C Note 15
> 10
> 1.5
> 0.15
Resolution
Note 13
% FS
/bit
% of
range
Note 16
Appendix A -- Reference 3000 Specifications--
Potentiostatic Mode
Applied Voltage Range
Min
± 11
volts
Accuracy
DC zero offset
Gain
DC Bias
Max
Note 5
Typ
1
0.2
±8
mV
% setting
volts
Scan DAC ranges
Typ
± 6.4, ± 1.6, ± 0.4
volts
Drift
Max
< 20
µV/°C
Note 18
Noise and Ripple
1 Hz to 1 kHz
1 Hz to 200 kHz
Typ
µV rms
Note 19
Note 17
<5
< 20
Galvanostatic Mode
Maximum Full Scale Current
± 30000
mA
Note 12
Minimum Full Scale Current
300
pA
Note 12
Accuracy
Dominated by current to voltage
converter accuracy shown above
± 3.0 volts
Sig Gen Voltage for Full Scale Current
Auxiliary A/D Input (see Appendix D)
Range (differential)
Typ
±3
volts
Input voltage range
(either input)
Gain Error
Max
± 3.6
volts
Max
0.2
%
Input Impedance
a) as shipped
b) re-jumpered for high Z input
Typ
100
10
kΩ
GΩ
Note 20
Auxiliary D/A Output
Range
Typ
0 to 4.096
volts
Resolution
Typ
1
mV
0 to 45
°C
90 (non-condensing)
%
Storage and Shipping Temperature
-25 to 75
°C
Maximum Shipping acceleration
30
G
Environmental
Operating Temperature Range
Relative Humidity
Max
11 - 3
Appendix A -- Reference 3000 Specifications--
General
Power Input Voltage
Range 22 to 26
volts
Power
Max
W
120
Leakage Current
(floating, earthed Working Electrode)
Dimensions (approximate) (whd)
± 1 nA
Note 21
20 x 23 x 30
cm
Note 22
Weight (approximate)
5
kg
Note 22
Dimensions of External Power Adapter
(approximate)
Weight of External Power Adapter
(approximate)
7.5 x 5 x 22
cm
Note 23
900
grams
Note 23
NOTES:
1. a) Measured in potentiostatic mode with a high wattage 20 Ω load connected from counter electrode
lead to the reference lead and a 2 Ohm load between the reference lead and the working electrode
lead. The compliance voltage is measured using an external voltmeter across the 22 Ω load. Under
these conditions, the output current is approximately 1.4 A.
b) Measured in potentiostatic mode with a high wattage 3 Ω load connected from counter electrode
lead to the reference lead and a 2 Ohm load between the reference lead and the working electrode
lead. The compliance voltage is measured using an external voltmeter across the 5 Ω load. Under
these conditions, the output current is approximately 5 A.
2. Measured with a 4-terminal 0.05 Ω load, in potentiostatic mode.
3. Unity gain bandwidth and slew rate are correlated. Each has five settings, with the highest slew-rate
occurring at the highest bandwidth, down to the lowest slew-rate occurring at lowest bandwidth. Both
are measured with 20 kΩ between counter and reference and 100 Ω between the reference and the
working and working sense leads
4. Measured with an external function generator connected to the Ext Sig In BNC.
5. The Differential Electrometer Amps are Analog Devices AD8065 Op amps specially selected for low
Vos drift versus temperature. These amps have a dual input stage, with a JFET input over most of their
input range and a bipolar transistor input at input voltages greater than + 9.5 volts. They are only a
high impedance buffer from –12 volts to +9.5 volts, though they are a unity gain buffer over their
whole input voltage range.
6. The input current of the JFET inputs on the AD8065s is less than 6 pA. When the Bipolar input is
operative, the input current can be in the microamps. The specified current is only applicable at
voltages of 2 volts or less.
7. The differential impedance is measured between the Reference and Work Sense inputs. This is the
impedance you measure when you record the EIS spectrum of an infinite impedance cell.
There is also a common mode resistance and capacitance associated with the differential electrometer
inputs. These values tell you how much the electrometer response is modified by a resistance in series
with the source.
8. The bandwidth is for a sine-wave source with a 50 Ω output impedance driving either input. The
bandwidth is well in excess of this specification, which is limited by the measurement equipment used
in testing the Reference 3000.
9. CMRR is common mode rejection ratio. It specifies the ability of the differential electrometer to reject
signals connected to both inputs. The CMRR is measured driving both inputs with a sine-wave source
with a 50 Ω output impedance, and measuring the error as a function of frequency. Resistance in
either input will cause a loss of CMRR.
10. Voltage measurement is actually performed with a ±3 volt signal input to the ADC signal chain. A ÷4
attenuator divides down higher voltage electrometer outputs so they fit into a ±3 volt input, thus
11 - 4
Appendix A -- Reference 3000 Specifications--
making a ±12 volt full scale range. Gains of 10 and 100 are available to generate 300 mV and 30 mV
ranges.
11. The total error in a voltage measurement is:
Error = Zero Offset Error + Gain Error * Voltage
For a 1 volt signal the error can be as high as 3 mV.
12. There are 11 hardware current ranges, separated in sensitivity by decades. The ranges are: 300 pA, 3
nA, … 300 mA, 3 A full scale. The x10 and x100 gains add two virtual ranges of 30 pA and 6 pA full
scale.
13. The voltage across the current measurement resistor, Rm, is as shown. Slightly higher voltages may be
seen at the working electrode terminal on the cell cable, since the cable has both resistive and
inductive impedance.
14. The total error in a current measurement is:
Error = Input Current Offset + Range Zero Offset * FS Current + Gain Tolerance * Measured Current
For small currents (pA) the first term is usually dominant.
For large currents (uA), the first term can usually be ignored.
The units for the error are amps.
15. Drift can be approximated by simple drift in the Range Zero Error. In reality all three terms in the
equation above can have drift.
16. The Current to Voltage converter bandwidth is a function of the current range, the cell cable, and the
IEStability setting.. The bandwidth can be very low on very sensitive ranges. Longer cell cables add
capacitance and slow the current measurement.
17. The total error in a voltage setting is:
Error = DC Zero Offset + Gain * Voltage Setting
For a 1 volt signal the error can be as high as 3 mV.
18. This specification is guaranteed by design. It is not tested.
19. This specification is measured by applying zero voltage across a 1 Ω resistor and measuring current
noise on the 30 µA scale. 1 µV of voltage noise will create a current of 1 µA. The filters in the ADC
Chain for the I Signal are used to limit the bandwidths as shown in the spec.
Signal averaging via Gamry’s DSP mode will further reduce the measured noise.
20. See Appendix D.
21. Isolation quality has both DC factors and AC factors (predominately at the 300 kHz power supply
frequency). Only the DC leakage current is shown here. Consult Gamry’s technical support for
additional information.
22. Excluding external power adapter and any cables supplied with unit.
23. Excluding removable line cord.
11 - 5
Appendix B -- Reference 3000 Cell Connectors--
Appendix B -- Reference 3000 Cell Connectors
Chapter 5 describes the connections between a cell cable and an electrochemical cell. This appendix describes
the other end of the cell cable.
Multiple pins assigned to the same signal are connected together on the Reference 3000’s Potentiostat board.
If you need to connect this signal outside the Reference 3000, you need a wire connected to any one of the D
connector pins.
Table B-1
Counter/Working Connector
Pin(s)
1,9
2, 10
3
4, 6,11,13
Signal Name
Working
Working
Shield
No connect
Ground
5,12
7
Counter
CBL_ID1
8
CBL_ID2
14
CBL_ID0
15
CBL_ID3
Use
Connected to the working electrode (see Chapter 5).
The shield for the working electrode. Connected to Floating Ground on D
end of the cable Left open at the cell end of the cell cable.
The potentiostat's floating ground. Can be used to shield the cell if very low
currents need to be measured. Also used as a shield for the counter
electrode cable.
Connected to the Counter Electrode
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
12 - 1
Appendix B -- Reference 3000 Cell Connectors--
Table B-2
Sense Inputs Connector
Pin(s)
1
Signal Name
CBL_ID2
2
CBL_ID1
3,4
Ground
5,6,12,14
8
Reference
Shield
Work Sense
Shield
Work Sense
9
CBL_ID3
10
CBL_ID0
11
Counter
Sense
13
Reference
Electrode
7,15
Use
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
The potentiostat's floating ground. Can be used to shield the cell if very low
currents need to be measured. Also used as a shield for the counter
electrode cable.
The shield for the reference electrode input. Driven to the same potential as
Pin 16. Left open at the cell end of the cell cable.
The shield for the work sense electrode input. Driven to the same potential
as Pin 8. Left open at the end of the cell cable.
Connected to the working electrode in most cases (see Chapter 5). This lead
has a 261 Ohm resistor in the cell end of the cable. Custom cell cables are
likely to require a similar resistor.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
One of 4 cable ID bits. Used to identify the type of cell cable attached to the
unit. Pull to a logic High through a resistor. Ground to set the bit low.
Connected to the counter electrode in ZRA-mode and stack-mode
experiments (see Chapter 5). This lead has a 261 Ohm resistor in the cell end
of the cable. Custom cell cables are likely to require a similar resistor.
Connected to the reference electrode in most cases (see Chapter 5). This
lead has a 261 Ohm resistor in the cell end of the cable. Custom cell cables
are likely to require a similar resistor.
12 - 2
Appendix C -- Misc I/O Connector--
Appendix C -- Misc I/O Connector
This connector contains a number of signals, used to interface the Reference 3000 to external apparatus. It is
the miniature 15 pin female D shaped connector on the rear panel of the Reference 3000. Be careful, the
ground pins on this connector are not the Reference 3000 floating ground.
The metal shell of the D-connector is connected to the Reference 3000's Floating Ground. Improper User I/O
connections can damage an Reference 3000 that is connected to a high energy cell containing earth grounded
terminals.
The auxiliary analog output, derived from a D/A converter, is on this connector. The scaling is normally 1 mV
per bit, for a 0 to 4.096 volt full-scale range.
The pin out of this connector is shown in Table C-1.
Table C-1
Miscellaneous I/O Connector
Pin
1
2
3
Name
Analog Output High
Analog Output Low
Sync In
4
Sync Out
5
6
7
8
9
10
11
12
13
14
15
no connection
Ground
Digital Out 0
Digital Out 1
Digital Out 2
Digital Out 3
Digital In 0
Digital In 1
Digital In 2
Digital In 3
+5 Volts
Use
The auxiliary output signal (DAC output).
The auxiliary output ground connection (ground)
Used in slave mode – starts data acquisition
2.2 kΩ input impedance
A TTL pulse output before the start of a data point
330 Ω output impedance
Digital ground
A TTL compatible digital output- 330 Ω output impedance
A TTL compatible digital output- 330Ω output impedance
A TTL compatible digital output- 330Ω output impedance
A TTL compatible digital output- 330Ω output impedance
A TTL compatible digital input- 2.2 kΩ input impedance
A TTL compatible digital input- 2.2 kΩ input impedance
A TTL compatible digital input- 2.2 kΩ input impedance
A TTL compatible digital input- 2.2 kΩ input impedance
Power- 50 mA maximum current
Caution
Floating operation of Reference 3000 can be compromised by improper cabling to the
User I/O Connector. Do not use standard 15-pin shielded cables with this connector.
Custom cables with the shield connected to pin 6 of the D-connector are required.
13 - 1
Appendix D -- Auxiliary A/D Input Characteristics--Overview
Appendix D -- Auxiliary A/D Input Characteristics
Overview
The Controller board used in the Gamry Instruments Reference 3000 Potentiostat has jumpers or switches that
configure the input circuitry used for the Aux A/D function. Early units have jumpers and later units have
CMOS switches set using software. The changeover occurred in 2009.
We usually ask that you return your Reference 3000 to Gamry Instruments if you need to change the hardware
jumpers. This information is provided so a qualified service technician can change the Aux A/D input jumpers
in the field.
The CMOS switches are set using a function call in an Explain script. Once the CMOS switches are set, they
remain in the selected position until another script resets them. Note that the settings will return to their default
values on reset or Power Up of the Reference 3000.
Call or Email your local Gamry representative if you need to change your Auxiliary A/D input characteristics and
you are uncertain which type of control board you have.
Jumper Identification
The three jumpers that configure the Aux A/D input are in a cluster located at the upper right side of the
Controller Card. See the figure below for jumper locations.
14 - 1
Appendix D -- Auxiliary A/D Input Characteristics--
Figure D-1
Auxiliary A/D Input Configuration Jumpers
View of Reference Family Controller Board
Filter Jumper
Input Z Jumpers
Input Impedance Selection
Two jumpers are associated with the input impedance – J902 and J903. With J902 and J903 installed, the Aux
A/D input has a 100 kΩ input impedance. This is the default setting. With the jumpers installed, the
potentiostat can be calibrated without a cable on the input BNC connector.
With both J902 and J903 removed, the Aux A/D input impedance is 10 GΩ (typically). This setting is suitable
for use with a high impedance source such as a reference electrode. If you have removed these jumpers, do
not calibrate the potentiostat unless you have a cable connecting both Aux A/D inputs to floating ground.
The CMOS switch shorts the circuit nodes connected by these jumpers. As with the jumpers, in the Low
Impedance setting, the input impedance is set to 100 kΩ. In the high impedance setting, the CMOS switches
are opened increasing the input impedance to about 10 GΩ.
14 - 2
Appendix D -- Auxiliary A/D Input Characteristics--Bandwidth Selection
Bandwidth Selection
J900 (or on some boards J901) controls the bandwidth of the Aux A/D input. With J900 (or J901) removed,
there is no filtering on this input and the –3 dB bandwidth is greater than 300 kHz.
With J900 (or J901) in place (the default setting), a single pole RC filter is used to limit noise into the A/D. The
nominal cutoff frequency of this filter is 20 Hz.
Note that source impedances greater than 1 kΩ will appreciably lower this cutoff frequency. When the Aux
A/D input is driven by a source with an output impedance of 1 MΩ, the frequency cutoff will be less than 0.25
Hz.
The CMOS switch performs the same function as the jumper.
Aux A/D Specifications
Range
Input Impedance
±3.276 volts
100 kΩ (approx)
or
Low Impedance Selected
10 GΩ (typical)
High Impedance Selected
Input Bias Current
< 10 nA
High Impedance selected
Filter Cutoff
20 Hz ± 20%
With Low Bandwidth selected
Function Call to Set the Aux A/D BNC Characteristics
The CMOS switch is set using an Explain function call. The syntax of this call is:
Pstat.SetAuxBNCSettings (Impedance, Bandwidth)
Both variables passed to the function are Booleans (with a value of TRUE or FALSE).
The following definitions can be used to make a script that calls this function more readable.
#define SETAUXBNCSETTINGS_IMPEDANCE_HIGH TRUE
#define SETAUXBNCSETTINGS_IMPEDANCE_LOW FALSE
#define SETAUXBNCSETTINGS_BANDWIDTH_HIGH TRUE
#define SETAUXBNCSETTINGS_BANDWIDTH_LOW FALSE
A TRUE in the Impedance variable opens the switches across J902 and J903, selecting high input impedance. A
FALSE selects 100 k input impedance.
A TRUE in the Bandwidth variable opens the switch across J901, selecting high bandwidth. A FALSE selects low
pass filter at nominally 20 Hz.
14 - 3
Appendix E – Auxiliary Electrometer Specifications--DC Voltage Measurement
Appendix E – Auxiliary Electrometer Specifications
Unless otherwise mentioned, all specifications apply at 22° C, zero common mode voltage versus Ground FA,
input voltages with Zout < 10 Ohms, and all channel inputs (other than those of the channel under test) at zero
volts versus Ground FA. All measurements are made with the Aux Channel A/D with normal Framework
calibration.
DC Voltage Measurement
Offset Voltage
< 500 µV
20° C to 25° C
Temp Drift
< 10 µV/°C
from 0 to 45° C
Ranges
± 50 mV, ±500 mV, ± 5V
Full Scale
Differential Input Voltage
Resolution
1.666 µV, 16.66 µV, 166.6 µV
per bit
Differential Input Voltage
Gain Error
< 0.3%
on all ranges
Offset Range
± 5.12 V
offset of differential signal
Offset Resolution
166.6 µV/bit
Input Current
< 10 pA
zero volts input
measure by voltage
Common Mode
> 30 GΩ in parallel with
< 100 pF
-36V < Vcm < 36 V
versus floating ground
Differential
> 100 GΩ in parallel with
< 40 pF
-5V < Vdiff < 5 V
measured between
the two inputs
At all gain ranges
Input Impedance
Common Mode Rejection
CMR Range
-36 V < Vin < 36V
versus Floating Ground
CMRR
> 94 dB
> 86 dB
@ 3 Hz
@ 100 kHz
< -90 dB
< -80 dB
DC to 10 kHz
10 kHz to 100 kHz
Crosstalk
Low Frequency
High Frequency
15 - 1
Appendix E – Auxiliary Electrometer Specifications--Other AC Specifications
Other AC Specifications
Bandwidth
> 2 MHz
- 3 dB
Phase Shift
< 1°
< 3°
DC to 20 kHz
20 kHz to 100 kHz
Noise
< 4 µVpp
< 10 nV/Hz1/2
0.1 Hz to 10 Hz
at 1 kHz
15 - 2
Appendix F – CE Certificate--Declaration of Conformity
Appendix F – CE Certificate
Redefining Electrochemical Measurement
Declaration of Conformity
According to ISO/IEC Guide 22 and CEN/CENELEC EN 45014
Manufacturer's Name and Location:
Gamry Instruments
734 Louis Drive
Warminster, PA 18974
USA
This declaration is for the Gamry Instruments product models: Reference 3000
Potentiostat/Galvanostat/ZRA.
The declaration is based upon compliance with the following directives:
EMC Directive 89/336/EEC as amended by 92/31/EEC and 93/68/EEC
Low Voltage Safety Directive 73/23/EEC as amended by 93/68/EEC
The declaration is based upon product compliance with the following standards as defined in report
number R0295-000 from Ergonomics, Inc. for safety analysis and report number RSI-2772L from
Radiation Sciences, Inc. for EMC test and analysis.
EMC Standards
EN 61000-4-2
EN 61326:2002-2
Title
EMC – Electrostatic discharge, Immunity
EMC – Radiated Emissions
Low Voltage Directive
Safety Standards
EN 61010-1:2001
EN 61010-2-081: 6/2003
Class/ Criteria
B
A
Title
Safety requirements for electrical equipment for measurement, control and laboratory
use, Part 1: General requirements.
Safety requirements for electrical equipment for measurement, control and laboratory
use, Part 2 Particular requirements for automatic and semiautomatic laboratory
equipment for analysis and other purposes
Signature
Dr. Gregory A. Martinchek, PhD
Title: President
January 19, 2009
Date
Formal signed declaration is on file at Gamry, Inc.
16 - 1
Appendix F – CE Certificate--Certificate of Conformance
Certificate of Conformance
16 - 2
Comprehensive Index--
E Overload, 6-3
earth ground, 1-2, 9-6, 9-9
EasyUSB, 3-8
EIS speed, 9-8
electrical noise, 9-7
electrical transients, 1-6
electrons per second, 9-1
enclosed space, 1-4
environmental limits, 1-5
environmental stress, 1-4
External Signal, 6-7
Comprehensive Index
Auxiliary Electrometer Option, 7-1
AC adapter, 1-1
AC Adapter, 1-1
ADC channels, 3-6
AE Option - about, 2-2
air-cooling, 1-4
alligator clip, 5-3
ancillary apparatus, 9-9
authorization code \c chapter, 4-13
Aux A/D, 14-1
Aux In BNC, 6-8
auxiliary electrode, 5-2
Auxiliary Electrometer Specifications, 15-1
fans, 1-4
Faraday shield, 5-3, 9-6
filters, 3-6
firmware download, 6-2
firmware update, 4-14
floating ground, 5-2
Floating Ground, 6-4
floating ground binding post, 1-2
floating operation, 9-9
fluorescent lights, 9-7
black banana, 5-2
blue cell lead, 5-2
calibration, 4-16
calibration data, 3-8
capacitive cells, 8-1
CE Compliance, 1-6
cell cable
replacements and specials, 5-3
ZRA connections, 5-3, 5-4
cell cables, 5-1
Cell Connector, 12-1
cell connectors, 5-1
cell construction materials, 9-8
Cell LED, 6-2
Chassis Ground, 6-4
cleaning, 1-5
computer, 2-2
computer requirements, 4-3
computers - noise, 9-7
contract engineering, i
Control Overload, 6-3
conventions
notational, 2-3
Counter, 12-1
counter electrode, 5-2
Counter/Working Connector, 6-1
Gamry Framework, 2-1
green cell lead, 5-2
ground, 12-1, 12-2
hazardous live voltage, 1-1
Help system, 2-1
high frequency shunt, 8-3
high speed USB, 6-5
hints – cell design, 9-6
I Monitor BNC, 6-6
I Overload, 6-3
I/O connector, 6-6
input capacitance, 9-2
input current, 9-2
input impedance, 9-2
input leakage current, 9-5
inspection, 1-1, 4-2
installation, 4-1
Instrument Manager, 4-11
Instruments, i
Johnson noise, 9-3
data storage, 3-8
DC voltage, 3-9
DDS, 3-5
double insulation, 1-1
lead capacitance, 9-7
lead placement, 9-7
low I range dc calibration, 4-17
Luggin capillaries, 9-8
Luggin capillary, 8-2
E Monitor BNC, 6-7
17 - 1
Comprehensive Index--
small signals, 9-1
software calibration, 11-1
specifications, 11-1
stability, 8-1
state-machine, 3-6
static electricity, 1-6
storage, 1-5
support, i
materials, 9-8
MCE, 3-10
measurement system model, 9-1
membrane cell connections, 5-5
Misc I/O connector, 6-6
Misc I/O Connector, 13-1
miscellaneous I/O connector, 13-1
motors, 9-7
Multi Channel Electrometer, 7-1
telephone assistance, i
temperature, 1-4
thermocouple, 6-5
noise, 9-5
operation, 1-5
orange lead, 5-2
oscillation, 8-1
Overload LED, 6-3
Universal Dummy Cell, 4-16
USB cable, 4-5
USB firmware, 3-8
USB LED, 4-6, 6-2
USB port, 6-5
pin plug, 5-2, 5-4, 5-5
power brick, 1-1
Power Connection, 4-4
Power Cord, 4-4
Power In jack, 6-4
power LED, 4-5
Power LED, 6-1
power line transient, 1-6
Power PC, 3-8
Power PC firmware, 3-8
Power switch, 4-5, 6-4
power-up self-test, 4-5
problem,, i
Problems, i
visual inspection, 4-2
voltage noise, 9-5
Warranty, ii
white cell lead, 5-2
Windows Update, 4-7
Work Shield, 12-1
Working, 12-1
working electrode, 5-2
ZRA
cell connections, 5-3, 5-4
radio frequency, 1-6
radio transmitters, 9-7
red cell lead, 5-2
Reference 3000 - about, 2-1
Reference 3000 – manual overview, 2-1
reference electrode, 5-2
Reference Electrode, 12-2
reference electrode impedance, 9-8
reference electrodes, 9-8
RFI, 1-6
ringing, 8-1
safety, 1-1
schematic, 3-1
service, 1-5
service contract, i
shielding against noise, 1-2
shorting bar, 5-2, 5-4, 5-5
Sign Gen Out, 6-7
17 - 2
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