PC3 Potentiostat/Galvanostat/ZRA Operator's Manual · instruments differ primarily in their output...

PC3 Potentiostat/Galvanostat/ZRA

Operator's Manual

includes both

PC3/300 Potentiostat/Galvanostat/ZRA

and

PC3/750 Potentiostat/Galvanostat/ZRA

Copyright(c) 1993-99, Gamry Instruments, Inc. All rights reserved. Printed in the USA. Revision 3.10 June 2, 1999

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 one year from the date of shipment.

Gamry Instruments, Inc., makes no warranties regarding either the satisfactory performance of the PC3 or the fitness of the system 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 PC3 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 PC3 Potentiostat/Galvanostat/ZRA will work with all computer systems, operating systems, and third party expansion cards and peripherals.

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 and Trademarks

PC3 Operator's Manual Copyright 1993-99 Gamry Instruments, Inc. All rights reserved. Printed in USA.

Gamry Framework Copyright 1989-99 Gamry Instruments, Inc.

PC3, PC3/750, PC4, ECM8, 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

If You have Problems

Contact us at your earliest convenience. We can be contacted via:

Telephone (215) 682-9330 8:00 AM - 6:00 PM US Eastern Standard Time

Fax (215) 682-9331

Email [email protected]

Mail Gamry Instruments, Inc. 734 Louis Drive Warminster, PA 18974 USA

If you write to us about a problem, provide as much information as possible.

If you are having problems in installation or use of your PC3 (or PC3/750) Potentiostat/Galvanostat/ZRA, it would be helpful if you called from a phone close to your computer, where you can type and read the screen while talking to us.

We are happy to provide a reasonable level of free support for registered users of our products. Reasonable support includes telephone assistance covering the normal installation and use of the PC3 in standard computer hardware.

We provide a one year warranty covering both parts and labor. A service contract that extends the warranty is available at an additional charge.

Enhancements to the PC3 that require significant engineering time on our part may be available on a contract basis. Contact us with your requirements.

Table of Contents

Limited Warranty.................................................................................................................... i Disclaimers ............................................................................................................................. ii Copyrights and Trademarks..................................................................................................... ii If You have Problems .............................................................................................................. iii Chapter 1 -- Introduction ........................................................................................................ 1-1

About This Manual..................................................................................................... 1-1 CE Compliance Required for Sale in Europe............................................................... 1-1 About the PC3........................................................................................................... 1-1 PC3 Schematic Diagram ............................................................................................ 1-2 Notational Conventions ............................................................................................. 1-3

Chapter 2 -- Installation ......................................................................................................... 2-1 Computer Requirements............................................................................................ 2-1 Positional Conventions............................................................................................... 2-2 Handling the PC3 Card Sets ....................................................................................... 2-2 Dip Switches for System Configuration ....................................................................... 2-3 Installing the Cards in Your Computer ........................................................................ 2-4 Connecting the PC3 Interconnecting Cables ............................................................... 2-6 Cell Cable Installation ................................................................................................ 2-6 Application Software Installation and System Checkout .............................................. 2-7 Calibration................................................................................................................. 2-7

Chapter 3 -- Cell Cable Connections ...................................................................................... 3-1 CE Compliance, EMI and Cable Shielding .................................................................. 3-1 Potentiostat and Galvanostat Mode Cell Connections ................................................. 3-1 ZRA Mode Cell Connections...................................................................................... 3-3 Membrane Cell Connections...................................................................................... 3-5

Chapter 4 -- Stability in Potentiostat Mode............................................................................. 4-1 Capacitive Cells and Stability...................................................................................... 4-1 Improving Potentiostat Stability .................................................................................. 4-2

Appendix A -- PC3/300 Specifications ................................................................................... 5-1 Appendix B -- PC3/750 Specifications .................................................................................... 5-3 Appendix C -- Changing The Default PC3 Settings................................................................... 5-5

Overview................................................................................................................... 5-5 About the "GAMRY.INI" File ....................................................................................... 5-6 Changing "GAMRY.INI" using Setup............................................................................ 5-8 Using Notepad to alter "GAMRY.INI" .......................................................................... 5-9 Adding a New Potentiostat Card Set........................................................................... 5-9

Setting the Board Number Switches on a PC3 Potentiostat ............................ 5-9 Adding a Potentiostat Card Set to the Computer............................................ 5-10 Adding Potentiostat Information to "GAMRY.INI" using Setup ........................ 5-10 Manually Adding Potentiostat Information to "GAMRY.INI" ............................ 5-10

Removing a Potentiostat from a Framework System.................................................... 5-11 Interrupt Level Setting ................................................................................................ 5-11 Changing your I/O Register Address ........................................................................... 5-13 Changing the Auxiliary Analog Output Scaling ............................................................ 5-15 FRA Specification Within GAMRY.INI......................................................................... 5-15

Appendix D -- I/O Connections for the PC3 ............................................................................ 5-17 Grounds and the PC3 Potentiostat ............................................................................. 5-17 The Cell Connector.................................................................................................... 5-18 External Control Input................................................................................................ 5-19

Aux A/D Input ........................................................................................................... 5-20 Analog Monitor Connector......................................................................................... 5-21 Miscellaneous I/O Connector ..................................................................................... 5-22

Comprehensive Index ............................................................................................................. 6-1

Chapter 1 -- Introduction -- About This Manual

1-1

Chapter 1 -- Introduction

About This Manual

This manual covers the installation and use of the PC3 Potentiostat/Galvanostat/ZRA. It covers both the original PC3/300 Potentiostat/Galvanostat/ZRA and its cousin the PC3/750 Potentiostat/Galvanostat/ZRA. These instruments differ primarily in their output current: 300 mA for the PC3/300 and 750 mA for the PC3/750. Throughout this manual, the term PC3 should be interpreted as a reference to both the PC3/300 and the PC3/750.

This manual describes use of a PC3 with Revision 3.1 of the Gamry Framework software. It is equally useful when setting up a newly purchased potentiostat or modifying the setup of a seven-year-old potentiostat for use with new software.

The bulk of Chapter 1 is an overview of the PC3's design and modes of operation. Chapter 2 contains PC3 installation instructions. Chapter 3 describes cell cable connections. Chapter 4 covers the difficult issues of potentiostat stability and approaches to prevent oscillation.

You will find dry technical material such as specifications, DIP switch settings, and connector pin outs in the Appendices.

This manual does not discuss software installation or operation.

Software support for the PC3 is described in the On-line Help for each of the applications programs. All the Gamry Instruments' applications that run under the Gamry Framework control the PC3 via a PSTAT object. See the Framework On-line Help for programming information.

CE Compliance Required for Sale in Europe

The European Community has instituted standards limiting radio frequency interference from electronic devices and mandating several safety requirements. Gamry Instruments has modified its instruments to comply with these standards. We are shipping CE compliant instruments to all destinations, not just to Europe. The relevant CE regulations include EN55022 Class B and EN60950.

About the PC3

The PC3 Potentiostat/Galvanostat/ZRA is a research grade electrochemical instrument compact enough to fit inside a computer. The PC3 offers features such as 8 decade current autoranging, extensive filtering, and both current interrupt and positive feedback IR compensation.

The PC3 is built on two printed circuits cards. Each card requires one expansion slot in an AT compatible computer. The cards are interconnected by 4 ribbon cables. Depending on the number of available slots, up to four PC3 card sets can be installed in one computer.

The first card is an XT (lower) height card. It is called the Floating Card. It contains the analog potentiostat circuitry, the signal generator (mostly D/A converters), and the A/D converter. This card is not directly

Chapter 1 -- Introduction -- PC3 Schematic Diagram

1-2

connected to the computer's AT bus, power supplies, or grounds. It communicates with the computer over optocoupled serial lines.

The second card is a full AT height card, called the Interface Card. It contains the digital interface between the PC3 and the computer's AT bus. An isolated DC/DC converter on this card takes up about 1/3 of the card's area. This converter uses the computer’s 5 volt supply as its input. On the PC3/300 the outputs of this converter are isolated ± 24 volt and 5 volt supplies required by the floating circuitry. On the PC3/750 the outputs are isolated ± 16 volt and 5 volt supplies.

PC3 Schematic Diagram

If you are not familiar with electronic schematics or potentiostats, you probably want to skip this section. This information is for expert use only and is not required for routine use of the PC3.

Figure 1-1 is a highly simplified schematic diagram. It shows the analog portion of the PC3 in its potentiostatic control mode. In galvanostatic mode, the feedback is taken from the I/E converter rather than from the Electrometer, but the circuit is otherwise similar.

Figure 1-1 PC3 Analog Circuits in Potentiostat Mode

M ux,G ainF iltering

Aux A/D

A/D

Cell

Counter

Ref

W orking

Aux A/D

E xt. S ignal

RmI/E

Electrometer

Cell Switch

C ontrolA m p

1X

1X

1X

Bias D/A

Scan D/A

CA Speed

Scan Resolution

E sig

Stability

W orkingS ense

I sig(i x R m )

Chapter 1 -- Introduction -- Notational Conventions

1-3

A few points concerning this schematic:

• All the amplifiers shown (except the control amp) are actually differential amplifiers. For the sake of simplicity, they are all shown as unity gain amplifiers.

• The adjustable resistors and capacitors are stepwise selectable using computer controlled switches. For example, there are 8 Rm and 8 CA Speed settings.

• There are two 16 bit D/A converters generating the computer controlled portion of the applied cell voltage.

• There is an inversion in the Ext. Control Input that is not shown on this simplified schematic. Positive one volt at this input generates negative one volt of applied cell voltage (measured as E working versus E reference).

• Both current and voltage are measured in a "4 terminal" configuration. This eliminates errors due to IR drop in the cell cable. Some of the connections required for this 4 terminal measurement are not shown on the schematic.

• The cell switch is actually two switches in series - a relay for low leakage and an FET switch for fast response.

• The differential electrometer's common mode characteristics are adjusted to insure that there is no positive feedback of the common mode voltage. The CMRR at 100 Hz is adjusted to be 74 dB. This value should apply from DC to 1 kHz. At 200 kHz, the CMRR falls to about 54 dB.

• Gains and resistor values are not shown.

• Some analog circuits, including overload protection and detection circuitry, positive feedback IR compensation, the auxiliary D/A converter, power circuits, and data acquisition controls are not shown.

• All digital circuits, including the AT bus interface, the timers, optocouplers, and digital I/O are not shown.

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.

• Hexadecimal numbers. Hexadecimal numbers are used for hardware related items such as I/O addresses. The Framework and this manual use the C programming language convention: all hexadecimal numbers have a prefix of 0x. For example, the default I/O addresses used by a PC3 Potentiostat card are 0x220 through 0x23F.

• File names and directories. Inside paragraphs, references to computer files and directories will be in quotes, for example: "WIN.INI" and "\FRAMEWORK\FRAMEWORK.EXE".

Chapter 2 -- Installation -- Computer Requirements

2-1

Chapter 2 -- Installation

A PC3 Potentiostat/Galvanostat/ZRA is only useful after it has been installed in an AT compatible computer.

If you purchase a Gamry Electrochemical Measurement System complete with a computer, we will install the PC3 (and the system software) to produce a "turn-key" system. You can ignore this chapter if you have purchased a turnkey system.

If you buy your own computer, add a PC3 to an existing system, or move an old PC3 to a new computer, you need to know how to install a PC3 into a computer. Read on.

Software installation is discussed in the Installation Manual for each software package. It will not be discussed here.

Computer Requirements

Before you install a PC3 into your own computer you must make sure that your computer meets these simple requirements.

• A computer based on one of the following Intel microprocessors - 486, Pentium, Pentium II, or a 100% compatible processor from another vendor.

• Two full length, full AT height expansion slots for each PC3 Card Set. One slot must have a 16 bit ISA or EISA bus interface. The ISA bus interface is commonly referred to as the "AT Compatible" bus. The PC3 will not work in PCI slots , Microchannel slots or Apple Macintosh computers.

• Up to 20 watts of power supply capacity for each PC3 Card Set. This is in addition to the power normally drawn by your computer and its expansion cards.

Gamry's Windows based software packages (especially the EIS300 EIS Software) may impose additional, more stringent, requirements.

Chapter 2 -- Installation -- Positional Conventions

2-2

Positional Conventions

Throughout this manual, reference will be made to positions on the cards that make up the PC3 Potentiostat. In order to avoid confusion, we will define some conventions that describe positions on the cards.

Assume:

• The card in question is lying on a table in front of you.

• The component side up of the card is up.

• The card edge (where the card plugs into the computer) is pointing towards you.

Under these assumptions, Figure 2-1 illustrates our positional convention.

Figure 2-1 Positional Conventions

Handling the PC3 Card Sets

The PC3 Card Set, like most electronic components, is susceptible to damage from static discharges and connection to live circuits. Some elementary precautions should be taken when handling and installing these cards.

• The PC3 Cards are shipped in anti-static bags. Leave the cards in these bags until you need to install them or reconfigure them.

• Always turn off your computer before plugging in the cards.

• If you need to leave a card out of its anti-static bag, such as when you change the DIP switches that configure the card set, lay the anti-static bag on a flat surface, then lay the card on top of the bag.

• Prior to handling the cards, you should momentarily ground yourself to eliminate any static charges on your body. A good way to accomplish this is to turn off your computer, then lightly touch your finger to an unpainted portion of the computer's metal chassis.

• Save the anti-static bags. You must use them if the cards are ever shipped while not installed in a computer. This includes occasions when the cards must be returned to Gamry Instruments, Inc. for repair.

Chapter 2 -- Installation -- Dip Switches for System Configuration

2-3

Dip Switches for System Configuration

Each PC3 Interface Card in your computer has two DIP switches on it. You can use these switches to configure the cards for use in a specific computer system.

In most cases you leave the switches in their factory set positions and forget they are there. The factory settings should work for all single potentiostat systems where the computer contains only "common" expansion cards. Common is defined for purposes of this discussion as devices such as standard video cards, GPIB adapters, serial & parallel ports, disk controllers, etc.

You only have to set these DIP switches if you have an I/O address or interrupt level conflict between your PC3 card(s) and another expansion card. You normally discover these conflicts when the new card set doesn't work or causes failures in other cards that used to work. Some sound cards and network interface cards are known to conflict with the default PC3 settings.

The default factory settings for a PC3 Potentiostat card set are:

• Board number = 1. This is the correct setting for systems containing a single PC3 Potentiostat. This setting must be changed on the second, third and fourth card sets added to a computer.

• Interrupt Level = 10. This level does not conflict with common AT compatible system functions and expansion cards.

• Board I/O address range = 0x220-0x237 (hexadecimal). This range is not used by common AT compatible expansion cards.

If you have questions about what the terms Interrupt Level or I/O Address Range mean, or think you may need to change the settings, consult Appendix C Changing The Default PC3 Settings.

Chapter 2 -- Installation -- Installing the Cards in Your Computer

2-4

Installing the Cards in Your Computer

NOTE: Please review the discussion on Handling the PC3 Card Sets earlier in this chapter prior to proceeding.

The following procedure is used to install a PC3 Card Set in your computer. It assumes that you are using the default configuration for the installed card set or that you have already configured the card for a non-standard configuration.

1. Turn off your computer.

2. Following your computer manufacturer's instructions, open up the computer to expose its expansion card slots.

3. Locate an empty full length expansion slot that has an AT (16 bit) interface. If necessary, remove the retaining screw and slot cover (the 'L' shaped metal bracket). Save the screw for use later.

4. Locate a second empty full length slot that is within 12 cm of the first. You may have to move some of your existing cards to get two suitable slots. Again, remove the retaining screw and slot cover, saving the screw for use later.

5. The two cards in the PC3 Card Set are known as the Interface Card and the Floating Card. The card with the gold fingers on the lower right edge and the two DIP switch blocks on the upper edge is the Interface Card. The card with the aluminum shield and BNC (Coax) connectors on its minipanel is the Floating Card.

6. Remove the Interface Card from its anti-static bag.

7. Plug the Interface Card into the slot with the AT interface. Make sure the card seats securely in the edge card connector on the motherboard. Secure the card in the slot using the screw from Step 3.

NOTE: All the gold fingers on the lower edge on this card must be in a motherboard edge connector. If they are not, you have plugged the card into an XT (8 bit) interface slot.

8. Remove the Floating Card from its anti-static bag. Note the large BNC connectors on the right side of this card. As you insert this card into the second expansion slot, you must tilt it so that these connectors enter the rear panel before the rest of the card slides into the card guide. Do not secure the card in its slot yet.

9. Find the 10 pin ribbon cable originating on the minipanel of the Interface Card. This cable is used to route analog signals on the Floating Card to the Analog Monitor Connector. Connect the ribbon cable to the 10 pin grid located under a rectangular hole in the middle of the aluminum shield covering the Floating Card. The colored line on one edge of the ribbon cable should be toward the bottom of the of the Floating Card. See Figure 2-2.

The ribbon cable may lie along the front of the card or the back of the card (as shown in Figure 2-2). Make sure that this ribbon cable is not cut or abraded by contact with the pins on the solder side of the adjacent card.

10. Seat the Floating Card securely in the expansion slot and use the screw from Step 4 to secure it.

11. Do not close up the computer yet.

Chapter 2 -- Installation -- Installing the Cards in Your Computer

2-5

Figure 2-2 Monitor Point Connector on the Floating Card

Figure 2-3 Ribbon Cable Connectors on the PC3 Cards

Chapter 2 -- Installation -- Connecting the PC3 Interconnecting Cables

2-6

Connecting the PC3 Interconnecting Cables

Three additional ribbon cables connect the Interface and Floating Cards. The following procedure is used to connect these cables.

1. In all cases, the ribbon cables connect headers near the upper edge of each card. The colored stripe on the ribbon cable always goes toward the left side of the card. The cables are keyed to reduce the chances that you plug them in incorrectly.

2. The smallest cable (10 pins) goes on the left side of both cards.

3. The largest cable (26 pins) goes on the middle connector of both cards.

4. The mid sized cable (20 pins) goes on the right most connector of both cards.

5. Refer to Figure 2-3 if you're unsure about the location of the connectors.

6. Once all the cables are connected, carefully double check your work. Make sure that the colored stripe on the cable is always to the left, and that the connector is correctly placed on the pin grid.

CAUTION: The connector keying does not prevent one type of connector misalignment. You can easily miss an entire row of pins in one of the connectors. This error most often occurs on the 20 pin connector. Make sure that both rows of pins are in the connector.

7. Once this step is completed you may close up the computer.

Cell Cable Installation

The Cell Connector is a 9 pin female D shaped connector on the Floating Card. It is located just above the two BNC connectors on the card. This connector is used to connect the PC3 to the electrochemical cell being tested. Normally you make your cell connections using the cell cable that Gamry provides you.

Caution: Other PC functions can use female 9 pin D connectors. Make sure that your cell cable is plugged into the correct connector before making any connection to your cell.

The standard cell cable has a 9 pin D connector on one end and a number of leads terminated with banana plugs on the other. The D connector end of the cable is connected to the Cell Connector on the Floating Card. The screws on this cable should always be used to hold this cable in place.

Chapter 2 -- Installation -- Application Software Installation and System Checkout

2-7

Application Software Installation and System Checkout

Software installation is slightly different for each Gamry Instruments, Inc. application package. Refer to the software installation instructions in the Installation Manual for each application package in your system.

Many applications include a system checkout procedure. You should perform this procedure for each of your applications that has one. Follow the instructions in the application's Installation Manual. The system checkout procedures check for correct hardware and software installation. They are not a comprehensive test of each facet of system operation.

Calibration

After you have run the system checkout procedure(s), you should calibrate each PC3 card set installed in your system. A calibration script is provided with the Gamry Instruments, Inc. Gamry Framework. The Installation Manual for every major application package contains instructions for calibration using this script.

PC3 calibration can be done with either the PC3’s internal resistive dummy cell or an external resistive dummy cell. Calibration with the external resistor is more accurate, so it is preferred. A suitable 100 Ω 1% accurate resistor was shipped with your software and/or PC3. Please place this resistor in a safe place where you can find it if your unit requires recalibration.

If you do need to recalibrate and you cannot find the resistor shipped to you, you can substitute another 100Ω resistor. Its wattage and tolerance are unimportant.

Figure 2-4 Calibration Resistor Selection

The dialog box shown above allows you to select the resistor used during calibration. Click Yes to use the external resistor. Click No to use the internal resistor.

Potentiostat calibration is only required infrequently. You should recalibrate under the following circumstances:

• You are installing a potentiostat card set into a new computer or moving a card set into a different computer. The potentiostat should be calibrated in the new machine.

• 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.

• You have replaced your "GAMRY.INI" file.

Chapter 3 -- Cell Cable Connections -- CE Compliance, EMI and Cable Shielding

3-1

Chapter 3 -- Cell Cable Connections

CE Compliance, EMI and Cable Shielding

The European Community has instituted standards limiting radio frequency interference (EMI) from electronic devices. Compliance with these standards requires that special shielded cell cable connections are used in all CE compliant systems. The PC3 is electrically floating. Its connections to the electrochemical cell under test are not connected in any way to earth ground. While this is advantageous for testing many types of electrochemical systems, it can result in significant radio frequency (RF) interference. The interior of a personal computer is filled with RF energy. The computer's earth grounded enclosure prevents the escape of this energy. Now consider the case of the PC3. It is a floating potentiostat built on a board that mounts inside the computer. The floating circuits inside the computer act as an antenna, picking up RF energy. The potentiostat's cables then radiate this energy outside of the enclosure, generating RF emissions larger than those allowed in the regulations. Our older cell cables were only shielded with floating voltages. Floating shields prevent noise pickup but do nothing to prevent RF emissions. We have added an overall earth ground shield to the new CE compliant cell cable. This new shield effectively extends the computer's enclosure around the cable, lowering RF emissions. The new cable is interchangeable with the old cable. Unfortunately, the shield cannot extend over the entire cable length. In its final 25 cm the cell cable divides into 5 separate leads, which cannot be earth shielded. To remain CE compliant, a system with a PC3 must be used with an earth grounded Faraday shield around the cell, so that these separate leads are shielded. PC3 based systems that measure ZRA mode electrochemical noise and/or galvanic corrosion use an additional cable (the Aux A/D cable) to measure the cell's voltage. In older systems we used a coaxial cable for this function. This cable was an additional source of RF emissions. In CE compliant systems we use a new twinaxial cable with an earth grounded outer shield. Again, the final 25 cm of the cable are not covered by this earth ground shield. Unfortunately, this new cable requires an entirely different connector (Twin BNC) so it is not interchangeable with older cables.

Potentiostat and Galvanostat Mode Cell Connections

Each PC3 in your system was shipped with a standard cell cable.

One end of the cable ends in a 9 pin connector. This end connects to the PC3 Floating Card. Make sure you connect the cable to the correct 9 pin connector on the computer - video cards, among others, often include 9 pin female connectors. The minipanel for the PC3 Floating Card is easy to tell from those of other cards. It has two BNC (coaxial cable) connectors below the cell connector.

You should always screw the cell cable into place, since this cable comes off the card easily otherwise.

Chapter 3 -- Cell Cable Connections -- Potentiostat and Galvanostat Mode Cell Connections

3-2

The other end of the cell cable terminates in a number of banana plugs and one pin jack. There are three versions of the cell cable:

• The newest CE compliant cable that includes an Orange Counter Sense lead and a short black earth ground lead.

• An older CE compliant cable that does not include the orange lead.

• The original, non-CE compliant cable that has neither the short black nor orange lead.

One cell cable design is shared by the Gamry Instruments’ PC3 Potentiostat, the PC4 Potentiostat and the ECM8 Electrochemical Multiplexor. The new orange lead is used in PC4 connections and some ECM8 connections. It is not needed in PC3 cell connections.

Note: The part number for the standard cell cable (ending in banana plugs) did not change. It did go to new revision levels. Old and new cables are interchangeable, except for CE compliance. Only a new cable, with its extra black banana plug may be used in CE compliant systems.

Table 3-1 identifies each terminal of the cable. It’s OK if your older cable is missing the orange and/or short black leads shown in this table.

Note: The PC3 is CE compliant (approved for sale in Europe) only when used with a CE compliant cable and an earth (chassis) grounded Faraday Shield. Without this shield, the PC3 radiates excessive Electromagnetic Interference (EMI). All European installations must use a Faraday shield connected to the short black cell lead, or they will not be CE compliant. The entire 25 cm length of the individual cell leads (green, blue, red etc.) must be confined within the shield. You can use an older PC3 (one with no CE markings) without a shield because it was purchased prior to the enforcement of the CE EMI requirements.

Table 3-1

Potentiostat and Galvanostat Cell Cable Terminations on All Three Cell Cables

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 Leave open (used only with PC4 or ECM8)

Long Black Banana Plug Floating Ground Leave open or connect to a Faraday shield

Short Black Banana Plug Chassis Ground Connect to Faraday Shield to reduce EMI

Note: ZRA Mode uses different cell connections. See the next section in this chapter for details.

Chapter 3 -- Cell Cable Connections -- ZRA Mode Cell Connections

3-3

Connect both the blue and green cell leads to the working electrode. The working electrode is the specimen being tested. The blue banana 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 1.5 volts above the circuit 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.

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 PC3's power amplifier.

The orange lead, if present, is not used when making PC3 cell connections. It is used with the Gamry Instruments’ PC4 Potentiostat and in some cases with the ECM8 multiplexor.

The longer black banana plug is connected on the PC3 end to Floating Ground. This is the circuitry ground for the analog circuits in the PC3. In most cases, this terminal should be left disconnected at the cell end. When you do so, take care that it does not touch any of the other cell connections.

The shorter black lead is connected to the computer’s chassis (earth) ground. In European CE compliant systems, it must be connected to a Faraday shield that completely surrounds the cell.

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 longer black cell lead to a source of earth ground. The short black lead or a water pipe can be suitable sources of earth ground.

Caution: If any electrode is at earth ground, you must not connect the black cell lead to earth. Autoclaves, stress apparatus, and field measurements may involve earth grounded electrodes.

When you are measuring very small currents, you may find that a metal enclosure completely surrounding your cell (a Faraday shield) will significantly lower the measured current noise. This Faraday shield should be connected to the short black cell connector. If your electrodes are all isolated from ground, you should also connect the shield to the longer black lead.

The alligator clip on a 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 provide additional standard or special cell cables. Contact us if you have unique cable requirements, such as extra long cables or special connectors.

ZRA Mode Cell Connections

The PC3 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. Optionally, it can use the Aux A/D Input to measure the potential of the samples versus a reference electrode.

Different cell connections are required when a PC3 is used in ZRA mode. The cell cable connections are shown in Table 3-2. Some cell leads may not be present on older cell cables. If this is the case, the entries in the table for these leads can be ignored.

Chapter 3 -- Cell Cable Connections -- ZRA Mode Cell Connections

3-4


Table 3-2 Cell Cable Connections for Galvanic Corrosion


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 metal sample #2

Red Banana Plug Counter Electrode Connect to metal sample #2




Aux A/D Cable Connections for Galvanic Corrosion


Blue Banana Plug Aux A/D -in Connect to metal sample #1

White Pin Jack Aux A/D +in Connect to reference electrode

The reference lead and the working sense lead are each connected to one of the metal samples. In the ZRA mode the PC3 is programmed to maintain zero volts between these leads. It therefore maintains the two metal samples at the same voltage.

The Aux A/D Cable provided with your system can be used to measure the metals' potential versus a reference electrode. The white pin jack on this cable is connected to the reference electrode and the blue banana plug is connected to the working electrode. The end of the cable with the BNC connector is connected to the Aux A/D input on the PC3 Floating card. This is the upper connector of the two BNC connectors on the card. The maximum potential that can be read on the Aux A/D is ± 3 volts.

Chapter 3 -- Cell Cable Connections -- Membrane Cell Connections

3-5

Membrane Cell Connections

The PC3 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 contains a counter electrode. The PC3 controls the potential across the membrane. Table 3-3 shows the cell connections used with a membrane type cell.

Some cell leads may not be present on older cell cables. If this is the case, the entries in the table for these leads can be ignored.


Table 3-3 Cell Cable Connections for a Membrane Cell


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




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.

Chapter 4 -- Stability in Potentiostat Mode -- Capacitive Cells and Stability

4-1

Chapter 4 -- 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 already phase shifted feedback signal. 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 of the electrical double layer that 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 PC3 Potentiostat is often 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 PC3 has been tested for stability with cell capacitors between 100 pF and 1000 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 PC3 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 PC3'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.

Chapter 4 -- Stability in Potentiostat Mode -- Improving Potentiostat Stability

4-2

Improving Potentiostat Stability

There are a number of things that you can do to improve an unstable or marginally stable PC3 potentiostat/cell system. This list is not in any particular order. Any or all of these steps may help.

• Slow down the potentiostat. The PC3 has 8 control amplifier speed settings, which can be selected in software. Slower settings are generally more stable. See the description of the Pstat.SetCASpeed function in the Framework On-line Help for details on setting the PC3's speed from Explain.

• Increase the PC3 I/E stability setting. The PC3 includes 2 capacitors that can be paralleled with its I/E converter resistors. These capacitors are connected to relays that are under software control. See the description of the Pstat.SetStability function in the Framework On-line Help for details on changing the PC3 stability setting from Explain.

• 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 Lugin capillaries. If you do have a Lugin capillary, make sure that the capillaries' 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 4-1. 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 4-1 Fast Combination Reference Electrode

SCE Platinum

WhiteCell Lead 100 pF to 10 nF

Electrolyte


4-3

• 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 4-2. The capacitor value is generally determined by trial and error. One nanofarad 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 4-2 High Frequency Shunt

Red

White

Blue

Green

100 pF to 10 nF

CounterReference

Working


4-4

• Add resistance to the counter electrode lead to make the cell less capacitive. See Figure 4-3. 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 100 µA, you can add a 10 kΩ resistor.

Figure 4-3 Resistor Added for Stability

Red

White

Blue

Green

CounterReference

Working

Resistor

Appendix A -- PC3/300 Specifications --

5-1

Appendix A -- PC3/300 Specifications

Control Amplifier

Compliance Voltage ± 20 volts @ 150 mA

Output Current ± 300 mA

Unity Gain Bandwidth 500 kHz (fast mode)

Slew Rate 8 V/µsec

Differential Electrometer

Input Impedance > 10 GΩ

Input current < 60 pA

Bandwidth (-3dB) > 5 MHz

CMRR > 70 dB (DC to 2 kHz)

Voltage Measurement

Full Scale Ranges ± 12V, ± 3V

Resolution 16 Bits

DC Accuracy ± 0.2% Range ± 1mV

Current Measurement

Full Scale Ranges ± 30 nA to ± 300 mA in decades

Resolution 16 bits

DC Accuracy ± 0.2% range ± 3 nA

Bandwidth (-3 dB) 500 kHz (30 µA--300mA)

100 kHz (30 µA)

1 kHz (30 nA)

Auxiliary A/D Input

Range ± 3 volts differential


Auxiliary D/A Output

Range ± 5 volts or 0 to 10 volts

Resolution 2.5 mV

ALL SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

Appendix A -- PC3/300 Specifications --

5-2

Environmental

Operating Temperature 0-70 °C (inside computer)

Specification Temperature 25 °C

Potentiostat Mode

Applied E Range ± 11 volts

Accuracy ± 2 mV ± 0.2% of setting

Scan Ranges 2 volts and 8 volts

Resolution 1/8 or 1/32 mV/bit

Drift < 30 µV/C

Noise and Ripple < 20 µV rms (1Hz - 10 kHz)

Galvanostat Mode

Applied i range ± full scale current

DC accuracy ± 0.2% full scale

Scan Ranges 2X full scale current

Current Interrupt

Measurement Type (sample 2 points on decay, extrapolate)

Cell Switching time < 1 µsec (1 kΩ cell )

Minimum interrupt time 15 µsec

Maximum interrupt time 64 msec

A/D converter

Resolution 16 bits

Accuracy 0.1% of full scale

Timing 50 µsec to 600 sec

Other

Monitors E,i,scan

External input 8 kΩ input Z

Power 18 W maximum (3.6A at 5 volts)

Leakage i, floating mode < 5 nA @ DC, 24 V out

Appendix B -- PC3/750 Specifications --

5-3

Appendix B -- PC3/750 Specifications

Control Amplifier

Compliance Voltage ± 12 volts @ 500 mA

Output Current ± 750 mA

Unity Gain Bandwidth 500 kHz (fast mode)

Slew Rate 8 V/µsec

Differential Electrometer


Input current < 60 pA

Bandwidth (-3dB) > 5 MHz

CMRR > 70 dB (DC to 2 kHz)

Voltage Measurement

Full Scale Ranges ± 3V and ± 12V (with ± 8V maximum reading)

Resolution 16 Bits

DC Accuracy ± 0.2% Range ± 1mV

Current Measurement

Full Scale Ranges ± 75 nA to ± 750 mA in decades

Resolution 16 bits

DC Accuracy ± 0.2% range ± 3 nA

Bandwidth (-3 dB) >500 kHz (750 µA--750mA)

>100 kHz (75 µA)

>1 kHz (75 nA)

Auxiliary A/D Input

Range ± 3 volts differential


Auxiliary D/A Output

Range ± 5 volts or 0 to 10 volts

Resolution 2.5 mV

ALL SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

Appendix B -- PC3/750 Specifications --

5-4

Environmental

Operating Temperature 0-70 °C (inside computer)

Specification Temperature 25 °C

Potentiostat Mode

Applied E Range ± 8 volts

Accuracy ± 2 mV ± 0.2% of setting

Scan Ranges 2 volts and 8 volts

Resolution 1/8 or 1/32 mV/bit

Drift < 30 µV/C

Noise and Ripple < 20 µV rms (1Hz - 10 kHz)

Galvanostat Mode

Applied i range ± full scale current

DC accuracy ± 0.3% full scale

Scan Ranges 2X full scale current

Current Interrupt

Measurement Type (sample 2 points on decay, extrapolate)

Cell Switching time < 1 µsec (1 kΩ cell )

Minimum interrupt time 15 µsec

Maximum interrupt time 64 msec

A/D converter

Resolution 16 bits

Accuracy 0.1% of full scale

Timing 50 µsec to 600 sec

Other

Monitors E,i,scan

External input 8 kΩ input Z

Power 22 W maximum (3.6A at 5 volts)

Leakage i, floating mode < 5 nA @ DC, 24 V out

Appendix C -- Changing The Default PC3 Settings -- Overview

5-5

Appendix C -- Changing The Default PC3 Settings

Overview

Your PC3 can be configured for your specific needs. DIP switches and jumpers on the PC3 allow you to:

• Choose the addresses used by the PC3.

• Choose the PC3 interrupt level.

• Reconfigure the PC3 as Pstat 1 through Pstat 4 in a multiple PC3 system.

• Alter the auxiliary analog output scaling.

Whenever a PC3 setting is changed, the software controlling that PC3 must be made aware of the change. The Gamry Framework reads the PC3's settings from an initialization file called "GAMRY.INI". This file lists the hardware configuration for any Gamry potentiostats in the system. It also contains software configuration information.

The "GAMRY.INI" file is located in the Windows directory. This ASCII text file is divided into sections identified by a section name in square brackets (e.g. [Framework]). Each section contains settings for a specific aspect of the system.

Turnkey systems are provided with a "GAMRY.INI" file appropriate for the items you have purchased with that system. The "GAMRY.INI" file in user installed systems is usually created by the Setup programs that come with the Gamry Framework and Gamry Instruments' application software. Setup can also be used to make changes in your system configuration.

Use this appendix when you need to make changes in the system configuration.

Appendix C -- Changing The Default PC3 Settings -- About the "GAMRY.INI" File

5-6

About the "GAMRY.INI" File

Gamry Instruments' Windows based software is configured by means of the "GAMRY.INI" file. The information in this file is used to:

• Identify each Potentiostat in the system.

• Determine the I/O address and interrupt level used by the system's potentiostats.

• Authorize use of a specific potentiostat by specific software packages.

• Store calibration data for each potentiostat.

• Store scaling factors for system D/A and A/D converters.

• Store software configuration information.

The "GAMRY.INI" file is an ASCII file. You can modify the file using an ASCII editor or a word processor in a non-document mode (a mode with no formatting codes in the text). The Windows Notepad accessory is a convenient ASCII editor.

The copy of "GAMRY.INI" actually used by the software must be located in the Windows directory (normally c:\WINDOWS). The Setup program provided with the Gamry Framework automatically installs "GAMRY.INI" in the correct directory.

A portion of a typical "GAMRY.INI" file is shown in Figure C-1. Only the information required for PC3 configuration is shown. A complete "GAMRY.INI" file is longer than this example.

Note: This sample “GAMRY.INI” file and the accompanying description are appropriate for Revision 3.1 of the Gamry Framework software. Previous software revisions used a somewhat different “GAMRY.INI” structure.

In Figure C-1, the 1st line is called a section identifier. The name of the section is enclosed in square brackets, e.g. [Framework]. The Framework section extends to the next section identifier [InterruptList]. The Framework section contains configuration information for the Framework program. This section is required in all "GAMRY.INI" files that configure a Gamry Framework System.

The [InterruptList] section contains entries for each interrupt that is used in the system. In the example, only IRQ10 is used.

The [DeviceList] section contains an entry for each potentiostat in the system. In the example, only one potentiostat is present in the system. Its configuration data will be found in a section labeled [Pstat0]. If the system included a second potentiostat, the [DeviceList] would include an entry for Pstat1 and there would be a [Pstat1] section in the .INI file.

The sample "GAMRY.INI" file also includes a [Pstat0] section. The following table describes some of the entries in this section.

Appendix C -- Changing The Default PC3 Settings -- About the "GAMRY.INI" File

5-7

Table C-1 Selected Fields in the [Pstat0] Section of the GAMRY.INI File

Field Name Data Type Range Description

Label text 7 characters Contains the text that is used to describe this potentiostat during Setup. Each potentiostat in the system should have a unique label.

CMSDriver text filename The dynamic linked library (DLL) that contains the software drivers for this potentiostat. Always PC3.DLL for a PC3.

IRQLevel number 5,10,11,15 The IRQ is used by this potentiostat. Must agree with DIP switch settings.

BaseAddress hex number see Table C-4 The start of the 32 byte range of I/O addresses used by this PC3. Must agree with DIP switch settings.

PstatClass text PC3 Always PC3 for a PC3/300 or a PC3/750. Other potentiostats belong to different classes.

BoardNo number 1, 2, 3 or 4 Each potentiostat in a multiple potentiostat is at a different board number. Must agree with DIP switch settings.

FraCurveClass text --- A description of the type of curve used to acquire EIS data with this PC3.

Fra text FRA1 to FRA4 Tells the system which FRA to use when acquiring EIS data with this PC3. Field missing in SoftFra only system.

AUXDACRES 2 numbers ---- The DAC resolution in volts per bit and a code that is 0 for bipolar output and 1 for a unipolar output.

The [Pstat0] section also contains potentiostat calibration information. In the sample, this data begins with the IFLTOFST = field and continues to the end of the section. You do not normally edit the calibration data which is automatically created and updated by the calibration routine built into the Framework.

Appendix C -- Changing The Default PC3 Settings -- Changing "GAMRY.INI" using Setup

5-8

Figure C-1 Portion of a Typical "GAMRY.INI" File

[Framework] LineFreq=60 PACKAGE0=DC105 [InterruptList] IRQ10= [DeviceList] Pstat0= [Pstat0] Label=PC3_1 CMSDriver=PC3.DLL IRQLevel=10 BaseAddress=0x220 PstatClass=PC3 BoardNo=1 FraCurveClass=FRACURVE3 AuthDC105=1234567890 AUXDACRES=2.5E-3,0 IFLTOFST=2 IPOFST=FF6C,FF9C,FF9D,FF9D,FFA2,FFA3,FFA3,FFF4 IGOFST=0,FFF1,FFF3,FFF3,FFF3,FFF4,FFF4,FFF4 VFLTOFST=FFFE VOFST=FFFA,FFF9 AOFST=FFFD GOFST=0 LASTOFST=FFF9 SCANOFST=FFFE,FFFE,8

Changing "GAMRY.INI" using Setup

The Setup program that comes with the Gamry Frameworkcan automatically make changes in the "GAMRY.INI" file. You can use the Framework Setup program to change the base address, the interrupt level and PStat identifier on the PC3's in your system. The Setup program for each Gamry Instruments' application software package can generally be used to alter the sections of the "GAMRY.INI" file that apply to that application.

Appendix C -- Changing The Default PC3 Settings -- Using Notepad to alter "GAMRY.INI"

5-9

Using Notepad to alter "GAMRY.INI"

It is often convenient to use an ASCII editor to make small changes in "GAMRY.INI". The Notepad accessory included with Windows is a useful ASCII editor. Please read the Microsoft Documentation for full instructions about using it.

Adding a New Potentiostat Card Set

To add a new potentiostat to a Framework system you need to do the following:

• Set the board number switches for the PC3 Potentiostat to be added.

• Add the potentiostat card set to the computer.

• Add potentiostat information to "GAMRY.INI".

Setting the Board Number Switches on a PC3 Potentiostat Each potentiostat in a multiple potentiostat system must be set for a unique board number. The board number is set using DIP switches on the PC3 Interface Card.

To change the board number switch settings on a PC3 card set proceed as follows:

1. Determine the desired board number for this PC3 card set. Board numbers should be sequential starting with board number 1. For example, a two potentiostat system has its cards configured as board numbers 1 and 2.

2. Locate the PC3 Interface Card. It is the larger card and it does not have a large aluminum shield covering most of the component side of the card.

3. Locate the two DIP switches on the upper middle portion of the card.

4. Locate S101, the bank of DIP switches on the left. See Figure C-2.

5. The ON position of the switches is marked on the body of the switch.

6. The order of the switches in S101 is S101-1 on the left, S101-8 on the right. This also is marked on the body of the switch.

7. Set the switches S101-1 through S101-4 from Table C-2. The switch settings are read across the row labeled with the desired board number. Do not change the settings of S101-5 to S101-8.

8. Double check that the change has been made correctly.

9. Label the outside of the metal bracket with the new board number.

Appendix C -- Changing The Default PC3 Settings -- Adding a New Potentiostat Card Set

5-10

Figure C-2 PC3 DIP Switch and Jumper Locations

Table C-2 Switch Setting for Different Board Numbers

Board S101- Number 1 2 3 4 1 ON OFF OFF OFF 2 OFF ON OFF OFF 3 OFF OFF ON OFF 4 OFF OFF OFF ON

Adding a Potentiostat Card Set to the Computer Please follow the instructions in Chapter 2 to install the new card set in the computer. You will need two full length card slots for each additional PC3 card set to be installed.

Adding Potentiostat Information to "GAMRY.INI" using Setup The easiest way to add the new information to "GAMRY.INI" is to rerun the Gamry Framework Setup program. You can skip over the file copy portion of Setup. Enter the new information in the dialog box that asks for potentiostat information.

Manually Adding Potentiostat Information to "GAMRY.INI" Before you can add potentiostat information to "GAMRY.INI", you need to understand how potentiostats are identified in the file. We will use the sample "GAMRY.INI" file in Figure C-1 as an aid in our discussion.

Look at the [DeviceList] section in Figure C-1. The line "Pstat0=" declares that there is a potentiostat in the system that is further described in a [Pstat0] section. A field labeled “Pstat1=” would identify a second potentiostat, “Pstat2” the third potentiostat, and so on.

Suppose you are adding another PC3 Potentiostat to this system. You must add the line:

Pstat1=

to the [DeviceList] section of your "GAMRY.INI" file.

You also must add a [Pstat1] section to the file. In general, you can copy the information in an existing section. Make sure that you change the BoardNo= field to match the setting on the board.

You may also have to add one or more authorization codes to the new [Pstat1] section of "GAMRY.INI". Each Gamry Instruments program requires a unique 10 digit authorization code before it will use a specific

Appendix C -- Changing The Default PC3 Settings -- Removing a Potentiostat from a Framework System

5-11

potentiostat. If the Framework does not find a valid authorization code, it will not take data. See the application’s Installation Manual for more information on this topic.

Your original shipping documentation should contain all the authorization codes that you need to operate your system.

If you do use Notepad to alter "GAMRY.INI", you must restart Windows before you can be sure the change to "GAMRY.INI" is effective.

Removing a Potentiostat from a Framework System

To remove a potentiostat from a system you need to do two things. The first is to physically remove the card set from the computer. The second is to remove the potentiostat's PstatX= field from the [DeviceList] section in the "GAMRY.INI" file (where X stands for the zero based board number of the potentiostat you are removing).

Interrupt Level Setting

Most peripheral devices in an AT compatible computer coordinate I/O (input/output) operations with the microprocessor by means of hardware interrupts. An interrupt is a request by a device that the computer suspend the program it's currently running, and perform an I/O operation. The PC3 Potentiostat generates an interrupt at the end of each data point.

An IBM AT compatible computer allows for 16 levels of hardware interrupts. In the Framework, all the potentiostats can use the same interrupt level. This interrupt level cannot be used by other system functions or expansion cards.

Unfortunately, very few of the 16 interrupt levels are not used by AT compatible system functions or the "common" expansion cards (e.g. video cards, serial ports, disk controllers, etc.). The interrupt levels available to the PC3 card set were chosen as those most likely to be free for PC3 use in a normal computer configuration. Table C-3 lists these levels along with any conflicts with levels assigned in the IBM AT Technical Reference Manual.

To change the interrupt level used by the potentiostats in your system, you need to perform two operations. First, the DIP switches on all the potentiostats in your system must be set for the correct interrupt level. Second, the "GAMRY.INI" software initialization file must be changed.

Table C-3 Interrupt Level Selection

Interrupt S102 Also Level 1 2 3 4 5 6 used for IRQ5 ON ON ON OFF OFF OFF LPT2 IRQ10 OFF ON OFF ON OFF OFF -- IRQ11 ON OFF OFF OFF ON OFF -- IRQ15 OFF OFF OFF OFF OFF ON --

NOTE: All the PC3 card sets in a computer are generally set for the same interrupt level.

Appendix C -- Changing The Default PC3 Settings -- Interrupt Level Setting

5-12

NOTE: Boards are shipped from the factory set for Interrupt Level 10.

If you have any uncommon expansion cards in your computer, you should consult their documentation to determine if they can generate system interrupts. If they can, you should determine their interrupt level setting(s), and select an Interrupt Level for your PC3 card set(s) that does not conflict with these cards.

For example, if you determine that your computer contains an ethernet card that generates interrupts on level 10, the interrupt level you choose for your PC3 card set(s) cannot be 10. Assume that you choose interrupt level 11.

The procedure for setting the S102, the interrupt level selector switches is:

1. Determine the desired interrupt level.

2. Locate the Interface Card from the card set. It is the larger card and it does not have a large aluminum shield covering most of the component side of the card.

3. Locate the two DIP switches on the upper middle portion of the card. See Figure C-2.

4. Locate S102, the switch on the right.

5. The ON position of the switches is UP, and is marked on the body of the switch.

6. The order of the switches in S102 is S102-1 on the left, S102-8 on the right. This also is normally marked on the body of the switch.

7. Set the switches S102-1 through S102-6 from Table C-3. The switch settings are read across the row labeled with the desired interrupt level. The switch settings for S102-7 and S102-8 don't matter.


9. Repeat steps 1-8 for any other PC3 Potentiostats in your system. Remember, the same S102 switch settings are generally used by all PC3 Potentiostats in the system.

The easiest way to change the interrupt level settings is to rerun the Setup program. The manual procedure for changing "GAMRY.INI" to reflect the new interrupt level is:

1. Edit "GAMRY.INI" in the Windows directory. Windows Notepad is a convenient ASCII editor.

2. In this file, locate the [InterruptList] section.

3. Add an entry for the new level (if its not already present). The entry has the form “IRQXX=” where XX is the level to be used. For the default IRQ setting the entry is "IRQ10=”.

4. Make sure that every [PstatN] section in the “GAMRY.INI” file has its IRQLevel field set to the new value. In the default file, each [PstatN] section should contain the line “IRQLevel=10”.

5. Save the edited file.

You must restart Windows before you can be sure the change is effective. If you have unsuccessfully attempted to run an experiment on the wrong level, you may have to power down and restart your computer before interrupts will occur normally.

Appendix C -- Changing The Default PC3 Settings -- Changing your I/O Register Address

5-13

Changing your I/O Register Address

The PC3 Potentiostat card set, like virtually all IBM compatible expansion cards, has hardware registers that the computer must be able to access. These registers are located at a specific address in the I/O (input/output) address space of the computer's microprocessor. Addresses are expressed in the hexadecimal numbering system where the digits are 1,2,3,4...8,9,A,B,C,D,E,F. We will always precede a hexadecimal number with the prefix 0x, e.g. 0x22F.

The PC3 Potentiostat requires 32 I/O register addresses. Unlike most cards, which cannot share I/O addresses, all the PC3s in a system are normally set up to use the same I/O register addresses. The board number assigned to each PC3 prevents harmful address clashes among PC3 cards. However, the I/O address range used by the PC3s still must not overlap with the I/O addresses used by any other device in your computer.

The 32 I/O addresses of the PC3 Potentiostat card can be selected to appear at a variety of locations in the I/O address space of the computer. Table C-4 is a list of the locations that can be set using DIP switches on the PC3 interface card. Addresses are given as a base (starting) address of the 32 byte I/O address range.

Table C-4 I/O Address Selection

Base S101 Address Range Address 5 6 7 hex decimal 0x220 ON ON ON 0x220-0x23F 544-575 0x240 ON ON OFF 0x240-0x25F 576-607 0x280 ON OFF ON 0x280-0x2AF 640-671 0x300 ON OFF OFF 0x300-0x31F 768-799 0x320 OFF ON ON 0x320-0x33F 800-831 0x340 OFF ON OFF 0x340-0x35F 832-863 0x100 OFF OFF ON 0x100-0x11F 256-287 0x120 OFF OFF OFF 0x120-0x13F 288-319

If you have any uncommon expansion cards in your computer, you should consult their documentation to determine the location of their I/O registers. If their register locations conflict with the default address range of 0x220-0x23F, determine a new base address from Table C-4 that does not conflict with any of your cards.

For example, suppose you determine that your computer contains a tape backup controller that uses I/O registers at addresses 0x230-0x23F. These clash with the default PC3 I/O addresses 0x220-0x23F. Therefore, the PC3 base I/O address must be changed. Assume that you choose a new base I/O address of 0x240. This base I/O address level and its associated S101 switch settings should be entered into the PC3 DIP switches and the "GAMRY.INI" file.

Appendix C -- Changing The Default PC3 Settings -- Changing your I/O Register Address

5-14

To change the I/O Address on your PC3 card sets, proceed as follows:

1. Determine the desired I/O address. See above discussion.

2. Locate the Interface Card from the card set. It is the larger card and it does not have a large aluminum shield covering most of the component side of the card.

3. Locate the two DIP switches on the upper middle portion of the card.

4. Locate S101, the switch on the left. See Figure B-2.

5. The ON position of the switches is UP, and is marked on the body of the switch.

6. The order of the switches in S101 is S101-1 on the left, S101-8 on the right. This also is normally marked on the body of the switch.

7. Set the switches S101-5 through S101-7 from Table C-4. The switch settings are read across the row labeled with the desired base address. Do not change the switch settings for S101-1 through S101-4.


9. Repeat 1-8 for any other PC3 Potentiostats in your system.

The procedure for changing "GAMRY.INI" to reflect the new I/O address setting is:

1. Edit "GAMRY.INI" in the Windows directory. Windows Notepad is a convenient ASCII editor.

2. In each [PstatN] section, locate the line BaseAddress=0xYYY, where YYY is the old I/O base address. For the default "GAMRY.INI" YYY is 220.

3. Enter the new base address in place of the YYY in this line. For example, if the new base address is 0x240, the line should read BaseAddress=0x240.

4. Save the edited file.

You must restart the Framework before you can be sure the change is effective.

Appendix C -- Changing The Default PC3 Settings -- Changing the Auxiliary Analog Output Scaling

5-15

Changing the Auxiliary Analog Output Scaling

Two jumpers on the PC3 Interface card allow you to change the scaling of the D/A converter used to generate the auxiliary analog output. These jumpers are J402 and J403, as seen in Figure C-2.

The PC3 leaves the factory set for a bipolar output of ± 5 volts with a bit resolution of 2.5 mV/bit. To obtain this setting, a jumper connects the upper two pins of J402 and a second jumper connects the lower two pins of J403.

To switch to a unipolar output, move the jumpers to the lower two pins of J402 and the upper pins of J403. The new scaling is 0 to 10 volts, still with a bit resolution of 2.5 mV/bit.

When you change to unipolar D/A scaling, you also need to make a change in the "GAMRY.INI" file. Under the [PstatN] section header, you need a field of the form:

AUXDACRES=2.5E-3,1

The final 1 indicates that the scaling is unipolar. If the final 1 was a zero, the scaling would be bipolar.

FRA Specification Within GAMRY.INI

If you do not have an external FRA attached to a specific potentiostat, the [PstatX] section for that potentiostat should not contain an Fra= field. The EIS300 software will assign the SoftFra as the only FRA available for a potentiostat that lacks the Fra= field. If you do have an external FRA associated with a specific potentiostat, the [PstatX] section for that potentiostat should contain an Fra field. The field should look similar to this:

Fra = FRA1

Other possible field contents include FRA2, FRA3 and FRA4. The “GAMRY.INI” file will contain a corresponding [FRA1] section that contains configuration information for that FRA. For example:

[FRA1] Label=SR810#1 Type=1 Port=1 Mode=COM1:9600,N,8,1

This section configures an SR810 Lock-in amplifier. It is known to the system by its label, SR810#1. It is a Type 1 device (like all other SR810s). Other external FRA devices (such as a different Lock-in amplifier model) would have a different type. This particular SR810 is connected to COM Port 1 and operated at 9600 baud, no parity, 8 data bits and one stop bit.

Appendix C -- Changing The Default PC3 Settings -- FRA Specification Within GAMRY.INI

5-16

Appendix D -- I/O Connections for the PC3 -- Grounds and the PC3 Potentiostat

5-17

Appendix D -- I/O Connections for the PC3

The PC3 Potentiostat has a number of connectors that allow it to communicate electronically with the world outside of the computer. This appendix describes these connectors and the signals available on their pins.

Grounds and the PC3 Potentiostat

The PC3 Potentiostat has been specially designed for operation with cells in which one of the electrodes is connected to earth ground. Conventional potentiostats do not work properly or safely with these cells. In the typical glass or plastic test cell, none of the electrodes are earthed, so no grounding problems arise.

The PC3 analog circuits are electrically isolated from the computer's chassis which is at earth ground. Another name for circuits that are isolated is "floating". The isolation is accomplished by means of optical isolators and transformers. The floating circuitry is all referenced to a floating ground, which is separate from earth ground.

Because of EMI considerations, the cell and final 25 cm of the cell lead must be shielded in a CE compliant system. The shield must be connected to earth ground. The short black banana plug on the cell connector is a suitable source for this ground. The shield surrounding the cell can be made of metal or metal screen. It must be continuous and completely surround the cell.

If your cell is isolated from earth ground, you should also connect the PC3's floating ground to this shield. When you do so, the shield acts as a Faraday shield which can significantly lower noise in the system. This is especially true if the currents in the cell are small or if your reference electrode has a high internal impedance. In this case the floating and earth grounds are both connected to the shield and are therefore connected together.

If your cell does contain earth grounded elements, do not connect the floating ground to earth ground! If you are working with earthed electrodes, ground connections for your potentiostat are critical. You must be careful that the floating ground connection on the cell cable is not connected to an earth ground. If it is connected to earth, in most cases measurements made with the system will be invalid.

One common error is to earth ground the potentiostat through ancillary equipment in the system. Connection of the PC3 to a signal generator, an oscilloscope, or a data acquisition system can connect the PC3’s floating ground to the ancillary equipment’s earth ground. In general, you should avoid connection of external test equipment to the PC3, unless it is absolutely required.

Appendix D -- I/O Connections for the PC3 -- The Cell Connector

5-18

Note: The PC3 is CE compliant (approved for sale in Europe) only when used with an earth (chassis) grounded Faraday Shield. Without this shield, the PC3 radiates excessive Electromagnetic Interference (EMI). All European installations must use a Faraday shield connected to the short black cell lead, or they will not be CE compliant. The entire 30 cm length of the individual cell leads (green, blue, red etc.) must be confined within the shield. You can use an older PC3 (one with no CE markings) without a shield because it was purchased prior to the enforcement of the CE EMI requirements.

The Cell Connector

The Cell Connector is a 9 pin female D shaped connector on the Floating Card. It is located just above the two BNC connectors on the card. This connector is used to connect the PC3 to the electrochemical cell being tested. Normally you make your cell connections using the cell cable that Gamry provides you. See Chapter 3 for a description of how the cell connections are made using the standard cell cable.

In the CE compliant version of the PC3, the metal shell of this D connector has been connected to the computer’s chassis (earth) ground. Older PC3s used a plastic D connector that did not allow for this connection.

In a few cases, you may find that you need to modify the cell cable or make a special purpose cable. By far the easiest changes involve modifying a standard cell cable. We can sell you an extra cell cable for this purpose. If you do need to make a completely new cable, the pinout of the cell connector is given in Table D-1. We recommend that you use shielded cables for all the cell connections. Coax cable is preferred. Connect the shield of the coax to the pin recommended in Table D-1 on the PC3 end, and leave the shield open on the cell end. Make sure that all pins are isolated from each other.

Cell cables longer than 3 meters may 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.

Appendix D -- I/O Connections for the PC3 -- External Control Input

5-19

Table D-1 Cell Connector

Pin Signal Name Use 1 Working Sense Normally connected to the working electrode. This is

the high impedance negative input of the differential electrometer.

2 WS Shield A driven shield for the working sense input. Normally connected to the outer shield of a coax cable on pin 1. Do not ground this pin!

3 Working Electrode The input to the PC3 current measurement circuit. The voltage on this point can be ±1.5 volt with respect to floating ground.

4 WE Shield A driven shield for the working electrode input. Normally connected to the outer shield of a coax cable on pin 3. Do not ground this pin!

5 Ground The PC3's floating ground. Should also be used to provide a shield for the counter electrode if one is used.

6 Ref Electrode Normally connected to the reference electrode. High impedance positive input of the differential electrometer.

7 Ref Shield A driven shield for the reference electrode input. Normally connected to the outer shield of a coax cable on pin 6. Do not ground this pin!

8 No Connect No connection on the PC3 circuit board. Used for Counter Sense in the PC4 Potentiostat.

9 Counter Electrode The output of the PC3 control amplifier. Normally connected to the counter electrode of the electrochemical cell being tested.

External Control Input

The External Control input allows you to inject a signal into the PC3's potential or current control circuits. One use for this input is modulation of the applied voltage or current. This input is the lower BNC connector on the PC3 Floating Card. Note that the shell of this BNC connector is connected to the PC3's floating ground.

In a CE compliant system, only earth ground referenced signals may be attached to the External Control Input. The outputs of virtually all line powered instruments, such as waveform generators, lock-in amplifier oscillators, and calibrators are earth ground referenced. With such a source connected, the PC3's isolation from earth is destroyed. Therefore the PC3 can not be used with earth grounded cells when the External Control Input is being used

In controlled potential mode (and ZRA mode), the potential applied to the cell is the sum of the applied potential and the control input voltage. For example, if the programmed voltage is +2 volts, and +1 volt is applied to the control input, the cell voltage (Ework - Eref) will be +3 volts. The input impedance of this input is 8 kΩ. Adding a control resistor, Rext, in series with the input allows you to alter the scaling factors. The equation describing the relationship is:

Vcell = Vsig x 8 kΩ/ (Rext + 8 kΩ)

Appendix D -- I/O Connections for the PC3 -- Aux A/D Input

5-20

Vsig is the signal applied to the resistor and Vcell is the resulting cell voltage. If 72 KΩ is added in series, a 1 volt signal will be attenuated to cause only a 100 mV cell voltage.

In controlled current mode, you will get full scale current for 7.5 volts applied to this connector. The current will vary with the current range. For example, on the 30 mA range, 2.5 volts will give you 10 mA of cell current. The sign is such that a positive input gives you a cathodic current.

Aux A/D Input

This input allows you to measure an externally generated voltage signal. On newer PC3s the Aux A/D input is a Twin BNC connector located on the PC3 Floating Card. A Twin BNC connector looks similar to a BNC connector, but has two central contacts and a shield contact. On older PC3s, the Aux A/D input is the upper BNC connector of the PC3 Floating Card.

One use of this input is to measure the cell potential in ZRA mode. Other possible uses include the measurement of temperature, strain, or other non-electrochemical parameters. This input is fully differential, with about 80 dB of common mode rejection. Be careful though, the allowed common mode voltage range is only ± 11 volts with respect to the floating ground. Voltages outside this range should not damage the instrument but they cannot be measured.

When this input is used for potential measurement in galvanic corrosion experiments, the Aux A/D cable provided with the PC3 should be used. The white lead on this cable is connected to a reference electrode. The blue lead is connected to your working electrode.

The scaling on this signal is ± 3 volts full scale, resulting in ± 30,000 counts on the A/D converter.

Appendix D -- I/O Connections for the PC3 -- Analog Monitor Connector

5-21

Analog Monitor Connector

This connector allows you to monitor selected analog signals within the PC3 potentiostat. The connector itself is the 9 pin male D shaped connector on the PC3 Interface Card. The connector is only mounted on the Interface Card because we had panel mounting space there. All its signals are derived from the Floating Card.

All the signals on this connector have a 330Ω output impedance. They are all referenced to the PC3 floating ground on pins 4 and 8 of the connector. If you are using the PC3 in a floating mode because you are using an autoclave, strain apparatus etc., be careful that your measurement equipment does not earth this floating ground. The signals on the analog monitor connector are contaminated with considerable 2 MHz noise from the PC3's system clock, and 150 kHz noise from its power supply. If you need to make high accuracy, fairly high bandwidth measurements of these signals, low pass filtering of the signal will be required. DVM type measurements should not require filtering.

The pinout for the Analog Monitor connector is seen in Table D-2.

Table D-2

Analog Monitor Connector

Pin Name Use 1 Electrometer Monitor The output of the differential electrometer. Normally

Eref-Ework. High bandwidth. 2 I filter out A filtered version of pin 6. Same scaling. See

PStat.IFilter description in Explain section of the Framework manual for bandwidth details.

3 Sum Monitor A voltage proportional to all the signals being applied to the cell. Includes IR compensation, constant biases and external signals.

4 Floating Ground The analog ground used by the PC3. Do not earth ground this pin if you need floating operation of the PC3.

5 Ref. Elect. Monitor The voltage of the reference electrode with respect to floating ground. This is different from the reference electrode with respect to the working electrode on pin 1.

6 I/E monitor A voltage proportional to current. 3 volt equals full scale current. High bandwidth. Switches with current range setting.

7 Scan Monitor A voltage proportional to changes in the signal waveform programmed in the experiment. This signal does not include IR correction, constant bias signals, or external control voltages. Scaling varies, but is never one to one with applied signal.

8 Floating Ground See pin 4 9 Work Elect. Monitor The voltage of the working electrode with respect to

floating ground.

Appendix D -- I/O Connections for the PC3 -- Miscellaneous I/O Connector

5-22

Miscellaneous I/O Connector

This connector contains a number of chassis ground related signals. It is the 15 pin female D shaped connector on the PC3 Interface Card. Be careful, the ground on this connector is not the PC3 floating ground. Connecting the two grounds may lead to problems if you are using the PC3 in a floating mode.

The auxiliary analog output, derived from a D/A converter, is on this connector. The scaling is normally 2.5 mV per bit, for a ± 5 volt full scale range.

The pinout of this connector is shown in Table D-3.

Table D-3 Miscellaneous I/O Connector

Pin Name Use 1 Digital In 0 A TTL digital input- 2.2 kΩ input impedance 2 Digital In 1 A TTL digital input- 2.2 kΩ input impedance 3 Digital In 2 A TTL digital input- 2.2 kΩ input impedance 4 Digital In 3 A TTL digital input- 2.2 kΩ input impedance 5 Digital Out 0 A CMOS digital output- 330 Ω output impedance 6 End Of Point* A 1 µsec TTL pulse at the end of each data point 7 Start of Point* A TTL pulse before the start of a data point 8 Analog Output Low The auxiliary output ground connection. 9 Analog Output High The auxiliary output signal. 10 No connect 11 Digital Out 1 A CMOS digital output- 330Ω output impedance 12 Digital Out 2 A CMOS digital output- 330Ω output impedance 13 Digital Out 3 A CMOS digital output- 330Ω output impedance 14 Ground Digital ground 15 +5 Volts Power- 100 mA maximum current

* These signals only present on Interface Board revisions C or higher. They can be used for oscilloscope triggering when troubleshooting.

Comprehensive Index --

6-1

Comprehensive Index [Framework] Section in GAMRY.INI, 5-6 0x for Hexadecimal Numbers, 1-3 alligator clip, 3-3 analog monitor connector, 5-20 Analog Monitor Connector, 2-4 anti-static, 2-2 Aux A/D

ZRA Mode, 3-4 aux A/D input, 5-19 auxiliary electrode, 3-3 BaseAddress, 5-7 black banana

longer, 3-3 blue cell lead, 3-2 board number, 2-3, 5-9 BoardNo, 5-7 calibration, 2-7

data, 5-7 capacitive cells, 4-1 CE Compliance, 1-1, 3-1 cell cable, 3-1

connections, 5-19 replacements and specials, 3-3 ZRA connections, 3-3

cell connector pinout, 2-6, 5-17

Gamry Framework, 1-1 CMSDriver, 5-7 common mode, 1-3 computer requirements, 2-1 conventions

notational, 1-3 positional, 2-2

counter electrode, 3-2, 3-3 Counter Sense lead, 3-2 DeviceList, 5-6 DIP switches, 2-3, 5-5, 5-9, 5-11, 5-12, 5-13, 5-14 earth ground, 3-3 EMI, 3-1 external control, 5-18 Faraday shield, 3-3 floating card, 1-1

floating ground, 3-2, 3-3 Fra, 5-7 GAMRY.INI, 2-7, 5-5, 5-6, 5-10, 5-11, 5-12 green cell lead, 3-2 grounds, 5-16 hexadecimal numbers, 1-3 high frequency shunt, 4-3 I/O address, 2-3, 5-13 I/O connections, 5-16 installation

card set, 2-4, 5-9 interface card, 1-2 interrupt level, 2-3, 5-12

changing, 5-11 InterruptList, 5-6 IRQLevel, 5-7, 5-12 longer black banana plug, 3-3 Lugin capillary, 4-2 membrane cell connections, 3-5 miscellaneous I/O connector, 5-21 Notepad, 5-6, 5-9 orange lead, 3-3 Orange lead, 3-2 oscillation, 4-1 PC3, 1-1, 5-9

floating ground, 5-16 installing, 5-9

PC3 Specifications, 5-1 PC3/750, 1-1 PC3/750 Specifications, 5-3 positions, 2-2 Potentiostat Stability, 4-2 Pstat.SetSpeed function, 4-2 Pstat.SetStability, 4-2 PstatClass, 5-7 red cell lead, 3-3 reference, 3-2 reference electrode, 3-3 removing a card set, 5-11 ribbon cables, 2-6 ringing, 4-1 schematic, 1-2

Comprehensive Index --

6-2

shorter black lead, 3-3 Software installation, 2-7 stability, 4-1 Stability, 4-1 static discharges, 2-2 stress apparatus, 5-16 system checkout, 2-7 turn-key system, 2-1 twinaxial, 3-1 Warranty, i white cell lead, 3-3 working electrode, 3-2 working sense, 3-2 ZRA

cell connections, 3-3

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