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Gamry Reference 620 Operator's Manual

Potentiostat/galvanostat/zra
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Reference 620
Potentiostat/Galvanostat/ZRA
Operator's Manual
Copyright © 2025 Gamry Instruments, Inc.
Revision 1.4
March 19, 2025
988-00086

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  • Page 1 Reference 620 Potentiostat/Galvanostat/ZRA Operator’s Manual Copyright © 2025 Gamry Instruments, Inc. Revision 1.4 March 19, 2025 988-00086...

  • Page 3: If You Have Problems

    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 620, please call from a phone next to your computer, where you can type and read the screen while talking to us.

  • Page 4: Disclaimers

    Gamry Framework, Echem Analyst 2, Echem ToolkitPy, Faraday Shield, and Gamry are trademarks of Gamry Instruments, Inc. Windows is a registered trademark of Microsoft Corporation. ® No part of this document may be copied or reproduced in any form without the prior written consent of Gamry Instruments, Inc.

  • Page 5: Table Of Contents

    Inspection ............................... 9 Product Safety ............................9 AC Mains Connection to the Power Brick ....................9 Grounding in the Reference 620 ......................10 Operation with Earth-Grounded Cells and Auxiliary Apparatus .............. 10 Temperature and Ventilation ......................... 11 Defects and Abnormal Stresses ......................11 Environmental Limits ..........................
  • Page 6 Blink Button ............................35 Changing the Label ..........................35 Introduction to the Reference 620 Customization Label ................. 36 Label Sheet Provided with Each Reference 620 ................36 Procedure to Change a Label ......................37 Chapter 5: Calibration ..........................39 Introduction ............................39 Factory Calibration ..........................
  • Page 7 Auxiliary A/D Input (see Appendix D) ....................77 Auxiliary D/A Output ..........................77 Environmental ............................77 General..............................77 Appendix B: Reference 620 Cell Connectors ....................81 Appendix C: Misc. I/O Connector ......................... 83 Appendix D: Auxiliary A/D Input Characteristics .................... 85 Overview .............................. 85 Aux A/D Specifications ..........................

  • Page 9: Chapter 1: Safety Considerations

    AC adapter (power brick), which outputs 24 V DC, which in turn powers the Reference 620. The Reference 620’s AC Adapter is rated for operation from 100 to 240 V AC, 47 to 63 Hz. It should therefore be useful throughout the world.

  • Page 10: Grounding In The Reference 620

    Grounding in the Reference 620 The circuitry and the metal case of the Reference 620 are not connected to an earth ground. If they were connected to earth ground, it would compromise the Reference 620’s ability to make measurements in electrochemical cells that contain earth grounded conductors.

  • Page 11: Temperature And Ventilation

    The User I/O connector can be connected to earth-grounded apparatus without earth-grounding the Reference 620, if the cable connections are done carefully. The metal shell on the Reference 620 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.

  • Page 12: Environmental Limits

    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 620 or any other apparatus if you think it could be hazardous. Have it checked by qualified service personnel. Environmental Limits There are environmental-limit conditions on the storage, shipping, and operation of this equipment.

  • Page 13: Rf Warning

    Reference 620 should not create an interference problem in most industrial laboratory environments. The Reference 620 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—...

  • Page 15: Chapter 2: Introduction

    It offers measurement capabilities similar to instruments that are more than ten times its size and weight and more than twice its price. The Reference 620 can operate as a potentiostat, a galvanostat, or a ZRA (zero-resistance ammeter).

  • Page 16: Notational Conventions

    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 are ® capitalized and placed within quotes, for example: “C:\MYGAMRYDATA\CV.DTA” and “GAMRY.INI”.

  • Page 17: Chapter 3: Instrument Circuitry

    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 620. The following figures are partly schematic diagrams and partly block diagrams. They are intended to show the basic principles of the Reference 620 circuitry without the confusion of the full circuitry details.
  • Page 18 The programmable attenuator on Esig prior to the ADC channel scales Esig so that it is compatible with the A/D channel’s ±3 V input range. The 0.25 gain setting allows the Reference 620 to measure potential signals slightly in excess of 10 V (on a 12 V full-scale range). Isig is gained to be 3 V full-scale so it does not require a similar attenuation function.
  • Page 19 • The DDS can generate fixed-amplitude sine waves with frequencies between 5 MHz and 1 mHz. In practice, Gamry’s electrochemical-impedance spectroscopy software uses the Scan DAC to generate sine signals if the frequency is below 20 Hz. The low-pass filter removes high-frequency distortion in the “raw” DDS output.
  • Page 20 Figure 3-3 One A/D Signal Chain in the Reference 620 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.
  • Page 21 ZSIG is the voltage of the cell cable’s counter sense lead minus the voltage on the Work Sense lead. It is called Zsig because this is the feedback voltage used in ZRA (zero resistance ammeter) mode. • Connection of the potentiostat’s CA input voltage to the Aux channel is reserved for use in future Gamry Instruments’ software and/or hardware projects.
  • Page 22 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 620 section of the Instrument Manager. Time-critical sections of the Power PC code are kept in the processor’s fast-cache memory.
  • Page 23 Notes for Figure 3-6: • Note the ground isolation between the input power and the Reference 620 circuitry. The Reference 620 chassis is connected to the Floating Instrument Ground. Transformers and isolators are the only components connected between the grounds.

  • Page 25: Chapter 4: Installation

    Front View of a Reference 620 Initial Visual Inspection After you remove your Reference 620 from its shipping carton, check it for any signs of shipping damage. If you find any damage, please notify Gamry Instruments, Inc., and the shipping carrier immediately. Save the shipping...

  • Page 26: Physical Location

    Physical Location Normally you place your Reference 620 on a flat workbench surface. You need access to the rear of the instrument because some cable connections are made from the rear. The Reference 620 is generally operated in an upright position (see Figure 4-1).

  • Page 27: Quick-Start Guide For System Installation

    Plug & Play configuration system. Like most Plug & Play hardware, it is best if you install the software for the Reference 620 before you install the potentiostat hardware. The latest Gamry software is not provided on a DVD anymore but is now available for download as *.exe or *.iso file on Gamry Instruments' Client Portal after creating an account and registering your instrument:...

  • Page 28: Power Cord And Power Connection

    Power Cord and Power Connection The Reference 620 does not plug directly in the AC mains supply. Instead, the mains are connected to an external power supply, which supplies a regulated 24-V DC output. This regulated DC is then connected to the DC Power In jack on the rear of the Reference 620 (see Figure 4-2).

  • Page 29: Power-Up Test

    620 (see Figure 4-2). One quick test is to power up the Reference 620 and watch the blue Power LED indicator on the front panel of the Reference 620 (see Figure 4-1). The Power LED should illuminate for a second or so, flash three times, then remain on.

  • Page 30: Front Panel Usb Led

    The D-type connector end of the cable is connected to the Cell Cable connector on the front of the Reference 620. Always use the knurled screws on this cable to hold the cable in place.

  • Page 31: Running The Framework

    Framework Device Status Bar By default, the Gamry Framework shows a Device Status Bar under its main menu (see Figure 4-3). If you don’t see the Device Status Bar when you run the Gamry Framework, it has been disabled in the Framework Options menu.

  • Page 32: Gamry Instrument Manager

    Framework with Three Potentiostats and One Running Test The Reference 620 (REF620-46052) in this system is shown with a green indicator because it is installed and ready to run. The Interface 1010 labeled IFC1010-01860 has a yellow indicator because it is recording the EIS spectrum shown on the screen.

  • Page 33: Change Tier Button

    Selecting an instrument that is connected and idle blinks its Power LED. After a moment, your potentiostat should appear next to Devices Present along with a green virtual LED. Repeat for additional potentiostats. Though no Reference 620 was used in this example, its functions apply in the same manner as described in this chapter.

  • Page 34: Firmware Update

    Firmware Update Your Reference 620 was shipped with the latest version of all its firmware. From time to time, Gamry makes changes to the instrument’s firmware code, and a firmware update is required to make use of the new or im- proved code.

  • Page 35: Select And Update

    Select And Update The Select And Update button is available at all times, even if an update is not required. Gamry recommends not altering the firmware if it is not necessary. This tool allows you to change individual firmware (instrument, PLD, Comm).

  • Page 36: Introduction To The Reference 620 Customization Label

    “Is the potentiostat to the left of my host computer the second or third potentiostat in the system? The Reference 620 includes a customization label that makes each unit visually unique. This allows you to know exactly which potentiostat will be used for each test. You can easily place other labels in the instrument’s Customization Label area.

  • Page 37: Procedure To Change A Label

    You can cut any of these labels from the sheet and insert as the Reference 620 Customization Label. The white labels are provided to allow you to handwrite a label. Procedure to Change a Label If you are making a custom-printed label, we recommend you edit the Excel® file available on www.gamry.com.
  • Page 38 8) Replace the black bezel. Reattach the four screws to fix the bezel in place. 9) Rename the Reference 620 in the Gamry Framework software to match the new label. Use the Framework Options > Instrument Manager... dialog box. In the resulting dialog box, select the device...

  • Page 39: Chapter 5: Calibration

    To maintain this traceability, you must return your instrument to a Gamry calibration site every one or two years. Gamry recommends User Calibration of the Reference 620 at least once per year, or when the quality of your data is in question.

  • Page 40: Calibrate Instrument

    User Calibration measures DC Offsets in the Reference 620 and corrects for them. It is most useful in eliminating current drift on the sensitive IE Converter ranges. User experiments and Calibrate Instrument run under similar environmental conditions will minimize errors.

  • Page 41: Calibrate Cable Capacitance

    3) You notice breaks or discontinuities in the data curves recorded with your system. 4) The system is being run in an environment that is very different from the previous operating environment. For example, if the Reference 620 was calibrated at 15°C and you are now operating it at 30°C, you should recalibrate.

  • Page 42: Procedure To Calibrate The Cable

    Figure 5-3 20 kΩ Calibration Cell The Reference 620 cable calibration calls for an external resistive dummy cell. Your Reference 620 was shipped with a 20 kΩ Calibration Cell including a 20 kΩ, 0.05% accurate resistor. After calibration, please place this Calibration Cell in a safe place where you can find it if your unit requires recalibration.
  • Page 43 Shield’s grounding post. (Note that the photograph below left is of a 200 Ω cell, so is only a general representation of the procedure.) 4) Open Gamry Framework™ software. Select Experiment > Named Script... The Select a script to run window appears.
  • Page 44 The Cable Capacitance Calibration window appears. 6) In the Cable Tag field, enter a unique name for the cable you are calibrating. Choose the desired Action radio button: To calibrate the cable, choose Cal Cable. To reset the vales to zero (if, say, the calibration doesn’t work), choose Zero Values. Click the OK button.

  • Page 45: Low I Range Dc Calibration

    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 620 current ranges: the 60 pA and 600 pA ranges. 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.
  • Page 46 Most corrosion experiments or macro-electrode measurements involve currents much too large to be affected by this difference. The Gamry Framework includes a special “Low I DC Current” calibration procedure that corrects the Reference 620 offsets to minimize this problem. The procedure uses a script that: 1.

  • Page 47: Chapter 6: Cell Connections

    ZRA mode, this lead may be left open as long as you ensure that it will not short against any other electrode. The black pin jack is connected on the Reference 620 end to Floating Ground. This is the circuitry ground for the analog circuits in the Reference 620.

  • Page 48: Zra Mode Cell Connections

    If any electrode in your cell is at earth ground, never connect the Reference 620 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 620 is provided for this purpose.

  • Page 49: Membrane Cell Connections

    Membrane Cell Connections The Reference 620 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 Reference 620 controls the potential across the membrane. Table 6-3 shows the cell connections used with a membrane type cell.

  • Page 51: Chapter 7: Panel Indicators And Connectors

    It is normally used with a Gamry Instruments-supplied cell cable. In addition to the pins used for cell connections, the Reference 620 Cell Connector also uses five pins to read a cell cable ID. Gamry’s software compensates for the cell-cable characteristics for optimal system performance, especially in EIS (Electrochemical Impedance Spectroscopy).

  • Page 52: Usb Led

    USB LED When the Reference 620 is first turned on, the Power LED glows 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.

  • Page 53: Cell On Led

    • The computer has disabled the USB port going to the Reference 620. The USB LED glows a steady green if a valid USB connection is made and the Reference 620’s communication processor is receiving power through the USB cable.
  • Page 54 Transient (temporary) overloads during an experiment in which the cell voltage or current is being stepped or swept are often normal. In most cases, they do not indicate a system or instrument malfunction. Consider the case of an infinitely fast voltage step into a perfect capacitor. In theory, charging the capacitor requires an infinite current.

  • Page 55: Rear Panel

    While a Reference 620 may work with other power sources, we cannot guarantee it will work to its full specifications. If you have to use the Reference 620 with a different supply, make sure that the supply is regulated, has an output between 22 and 26 V, and supplies 3 A of load current.

  • Page 56: Power Switch

    Power input voltages less than 20 V or greater than 32 V can damage the Reference 620’s power supply. Chassis Ground Power In jack Power Switch 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 620’s DC-DC converter.

  • Page 57: Chassis Ground

    USB Port The USB port on the rear panel of the Reference 620 is a Type B connector as defined in Revision 1.1 and 2.0 of the USB Specification. 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).

  • Page 58: Thermocouple Input

    A suitable USB cable was included with your Reference 620 shipment. If this cable is lost, replace it with a cable from your local computer retailer. The Reference 620 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...

  • Page 59: I Monitor Bnc

    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 de-aeration gas, and formation of mercury drops on a mercury drop electrode. •...

  • Page 60: E Monitor Bnc

    BNC. Its output impedance is approximately 200 Ω in parallel with 220 pF. E Monitor BNC The E Monitor BNC connector is the output of the Reference 620’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.

  • Page 61: Ext. Sig. In Bnc

    Ext. Sig. In BNC The Ext. Sig. In BNC connector allows you to add a voltage to the Reference 620’s signal generator. This signal is summed with the other signal-generator sources, including the IR DAC, the Scan DAC, and the DDS output.
  • Page 62 Consult Appendix D for additional information concerning this connector.

  • Page 63: Chapter 8: Stability In Potentiostat Mode

    The Reference 620 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.
  • Page 64 Figure 8-1 Fast Combination Reference Electrode White Cell Lead 100 pF to 10 nF Platinum Electrolyte • 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’s value is generally determined by trial and error.
  • Page 65 Figure 8-3 Resistor Added for Stability Resistor White Reference Counter Green Working...

  • Page 67: Chapter 9: Measurement Of Small Signals

    Chapter 9: Measurement of Small Signals Overview The Reference 620 is a very sensitive scientific instrument. It can theoretically resolve current changes as small as 1 femtoampere (1 × 10 A). To place this current in perspective, 1 fA represents the flow of about 6400 –15...

  • Page 68: Johnson Noise In Z Cell

    Figure 9-1 Equivalent Measurement Circuit R shunt C shunt Icell R in C in Unfortunately, technology limits high-impedance measurements because: • Current measurement circuits always have non-zero input capacitance, i.e., C > 0. • Infinite R cannot be achieved with real circuits and materials. •...

  • Page 69: Finite Input Capacitance

    AC signal by more than a factor of 10. The Reference 620 uses an input amplifier with an input current of around 1 pA. Other circuit components may also contribute leakage currents. You therefore cannot make absolute current measurements of very low pA currents with the Reference 620.

  • Page 70: Voltage Noise And Dc Measurements

    Water films can be a real problem, especially on glass. Shunt capacitance and resistance also occur in the potentiostat itself. The Reference 620 Potentiostat mode specifications in Appendix A contain equivalent values for the potentiostat’s R and C .

  • Page 71: Faraday Shield

    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 620’s floating-ground terminal. An additional connection of both the shield and the Reference 620 floating ground to an earth ground may also prove helpful.

  • Page 72: Cell Construction

    Z · f < 10 ·Hz Ancillary Apparatus Do not use the Reference 620 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 620 cell leads.

  • Page 73: Floating Operation

    Floating Operation The Reference 620 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 620’s internal ground is allowed to float with respect to earth ground when it works with these cells, hence the name “floating operation”.

  • Page 75: Appendix A: Reference 620 Specifications

    Appendix A: Reference 620 Specifications All specifications are at an ambient temperature of 25°C, with the Reference 620 powered using the external power supply shipped with the unit, a standard shielded 60 cm cell cable, and the cell enclosed in a Faraday shield.

  • Page 76: Current To Voltage Converter

    Reference 620 Specifications Current to Voltage Converter Maximum Full Scale Range Note 11 Minimum Full Scale Range Note 11 600 (after ×100 gain) mV (at Voltage across Rm Note 12 full scale) Output Voltage (at BNC and ADC in) (full scale)

  • Page 77: Galvanostatic Mode

    Reference 620 Specifications Galvanostatic Mode 600 Maximum Full Scale Current Note 11 60 Minimum Full Scale Current Note 11 Dominated by current-to-voltage Accuracy converter accuracy shown above Sig Gen Voltage for Full Scale Current 3.0 Auxiliary A/D Input (see Appendix D) 3...
  • Page 78 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 620. 9. CMRR is common-mode rejection ratio. It specifies the ability of the differential electrometer to reject signals connected to both inputs.
  • Page 79 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.

  • Page 81: Appendix B: Reference 620 Cell Connectors

    Multiple pins assigned to the same signal are connected together on the Reference 620’s Potentiostat board. If you need to connect this signal outside the Reference 620, you need a wire connected to any one of the D-connector pins.
  • Page 82 Reference 620 Cell Connectors Designing cell cabling for a 5 MHz potentiostat is not a trivial task. Gamry Instruments does not recommend user-designed cables (except as a last resort). In many cases we can build a custom cable to meet your specific needs. We’ll also be happy to discuss your cabling...

  • Page 83: Appendix C: Misc. I/O Connector

    Misc. I/O Connector Appendix C: Misc. I/O Connector This connector contains a number of signals; it connects the Reference 620 to external apparatus. It is the miniature 15-pin female D-shaped connector on the rear panel of the Reference 620. The ground pins on this connector are isolated from both the Reference 620 floating ground and earth ground.

  • Page 85: Appendix D: Auxiliary A/D Input Characteristics

    Appendix D: Auxiliary A/D Input Characteristics Overview The controller board used in the Gamry Instruments Reference 620 Potentiostat has software switches that configure the input circuitry used for the Aux A/D function. 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.

  • Page 87: Appendix E: Power Led Blink Codes

    If there are multiple problems, the communications board takes code priority over the memory module. Severe problem The red LED, which normally switches off after a rapid boot-up, remains illuminated. If you receive one of the above codes, please call Gamry Instruments Service Department for assistance.

  • Page 89: Appendix F: Certifications

    According to ISO/IEC Guide 22 and CEN/CENELEC EN 45014 Manufacturer's Name and Location: Gamry Instruments 734 Louis Drive Warminster, PA 18974 This declaration is for the Gamry Instruments product model: Reference 620 Potentiostat/Galvanostat/ZRA The declaration is based upon compliance with the following directives: • EMC Directive 2014/30/EU •...

  • Page 90: Certificate Of Conformance

    Certifications Certificate of Conformance...

  • Page 91: Declaration Of Conformity: No. Doc-2022-Ukca-Ref620

    Manufacturer's Name and Location: Gamry Instruments 734 Louis Drive Warminster, PA 18974 This declaration is for the Gamry Instruments product model: Reference 620 Potentiostat/Galvanostat/ZRA The declaration is based upon compliance with the following directives: • Electromagnetic Compatibility Regulations 2016 •...

  • Page 93: Appendix G: Index

    71 Blink, 35 Framework software, 31 blink codes, 87 Gamry Framework, 15 blue cell lead, 47 Gamry Instrument Manager, 31 Cable calibration, 39, 40 GIM, 32 Cable Capacitance Calibration, 44 green cell lead, 47 calcable.exp, 43 ground, 81...
  • Page 94 Power switch, 56 power-up self-test, 29 Quick Start Guide, 40 radio frequency, 13 radio transmitters, 71 red cell lead, 47 Reference 620 - about, 15 Reference Electrode, 47, 72, 81 reference electrode impedance, 72 Reference Shield, 81 RFI, 13 ringing, 63...

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