ompliance voltage is the voltage available at the counter electrode that can be used to force current to flow and still maintain control of the working electrode voltage.

How to Speak Potentiostat Compliance

Dr. Bobs Speaking Potentiosta ComplianceWhat’s important in the selection of a potentiostat? That depends greatly on its intended use. This page addresses an often misunderstood term.

Compliance voltagePotentiostat: Compliance Voltage

Compliance voltage is the voltage available at the counter electrode that can be used to force current to flow and still maintain control of the working electrode voltage. The compliance should be specified in conjunction with a current value: “20V @ 250mA” or “20V @ full rated current”. An amplifier’s output voltage decreases at higher currents due to the output impedance of the amplifier.


Favorite Electrochemistry EIS Books Availalbe

Selecting a Reference Electrode

My favorite My favorite reference electrode is the Ag/AgCl reference.electrode. Due to its simplicity, it is quite robust, and can be easily and effectively ‘revived’ if it should dry out. Moderately high temperatures ( 100 °C ) can be tolerated, as long as the AgCl does not completely dissolve and the construction materials are suitably Read more about Selecting a Reference Electrode[…]

The Working electrode is not at Virtual Ground

Potentiostat Architectures – Passive I/E Converters

A Common Potentiostat Design

This style of I/E Converter is well suited to potentiostats with output currents of a few tenths of an ampere up to several A Common Potentiostat Designamperes. This scheme has been used by Gamry, PAR, Solartron, and perhaps others.

The I/E Converter is a “passive” design

The current path through the I/E converter only traverses passive components such as wires and resistors. No active components (such as op amps or transistors) are in the current path. The current measurement resistor is connected between the Working electrode and the potentiostat’s power supply ground (or “current return”).

The Working electrode is not at Virtual Ground

This is a consequence of the passive design. The working electrode voltage (vs the potentiostat’s internal ground) depends on the current flowing. In the sketch shown to the right, the working electrode will be at (i*Rm) volts. The actual voltage may be higher due to the resistance of the cell cable connecting the potentiostat to the working electrode!

Potentiostat with differential electrometer


Reference Electrodes


This Application Note presumes that you have a basic understanding of potentiostat operation. If you are not that knowledgeable concerning electrochemical instrumentation, please read Potentiostat Fundamentals before continuing. Experienced potentiostat users may skip the primer and read on.

It’s only natural that electrochemists concentrate on the working electrode. After all, reactions at the working electrode are Silver Chloride Reference Electrodewhat they study. However, the reference electrode shouldn’t be ignored. Its characteristics can greatly influence electrochemical measurements. In some cases, an apparently “good” reference electrode can cause a complete failure of the system.

For reliable reference electrode performance, you should assign a “Lab Master” and treat it very, very carefully so it can serve as a standard for your other reference electrodes. Never use the Lab Master in an actual experiment. The only purpose of the Lab Master is to serve as a check for the other reference electrodes. If a reference electrode is suspected to be bad, you can check the potential versus the Lab Master. You can do that with a voltmeter, or with your Gamry Potentiostat by running and open circuit potential. If the potential difference is less than 2-3 mV, it’s OK. If it’s higher than 5 mV, it needs to be refreshed or discarded.


Gamry Interface - Reference Potentiostats

Potentiostat Fundamentals


A potentiostat is an electronic instrument that controls the voltage difference between a Working Electrode and a Reference Electrode. Both electrodes are contained in an electrochemical cell. The potentiostat implements this control by injecting current into the cell through an Auxiliary or Counter electrode.

In almost all applications, the potentiostat measures the current flow between the Working and Counter electrodes. The controlled variable in a potentiostat is the cell potential and the measured variable is the cell current.

Gamry Potentiostat


This Application Note may be difficult to follow unless you have some familiarity with electrical terms such as voltage, current, resistance, frequency, and capacitance. If you feel your knowledge in this area is lacking, we suggest review of a very basic electronics or physics book.


A potentiostat requires an electrochemical cell with three electrodes as shown below. W/WS denote the working and working sense. R denotes the reference electrode and C denotes the counter electrode.

Potentiosta: Electrochemical cell-3 electrodes […]

There is a description of potentiostat stability (written by DK Roe) in the Kissinger & Heineman book (

Converting Potentials to Another Reference Electrode

Often we find a potential listed in the literature quoted against a different reference electrode than the one we favor, or we would like to convert the potential to a more commonly used reference electrode for publication. A student emailed me: “My experiments involve measuring the redox potential relative to a saturated Ag/AgCl reference electrode. Read more about Converting Potentials to Another Reference Electrode[…]

Gamry Reference Electrodes

Potentials of Common Reference Electrodes

The following tables give the potentials of several commonly used reference electrodes. Various filling solutions are listed where data was available. Note that the nature and concentration of the filling solution can dramatically change the potential! When you look through the scientific literature, be sure the author has specified the filling solution! If you are Read more about Potentials of Common Reference Electrodes[…]

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