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.


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[…]

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

Potentiostat Stability

Contact Dr Bobs Buzz - Electrochemical Methods

A while ago I received an email from an electrochemist who lamented:

“We have some problems with the 173, which we still prefer to use occasionally  because of its analog nature. … (The) potentiostat goes into oscillations.”

Although the M173 has a reputation for ‘stability’ it has always had problems with oscillation! These problems tend to be most troublesome when the more sensitive current ranges are used and when the cell capacitance is large. PAR had a ‘noise filter’ in their catalog for a long time that was really a ‘stability aid’ more than a ‘noise filter.’ It consisted of a capacitor that was placed between the counter electrode lead and the input jack of the M178 electrometer. This acts as a shunt for the higher frequency, oscillation-producing signals. A capacitor value of 0.01 µF is a good place to start. I think this stands the best chance of stabilizing your system.


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