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

Posted on August 8, 2014May 29, 2018 by Dr.Bob

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

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.

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Potentiostats for Battery Research Testing

Posted on July 29, 2014June 26, 2015 by Dr.Bob

Take two different metals, place an ion transporting medium between them, wire them up to be connected outside the electrolyte solution (perhaps to a voltmeter or potentiostat) and you’ve made a battery. With the ever-increasing demand for portable power, batteries are becoming more and more important. As demands on battery performance increase, so do demands Read more about Potentiostats for Battery Research Testing[…]

The Working electrode is not at Virtual Ground

Potentiostat Architectures – Passive I/E Converters

Posted on July 7, 2014May 29, 2018 by Dr.Bob

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 Design amperes. 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

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Even if the I/E circuit is not overloaded, it can have severe influence on potentiostat stability.

Potentiostat Architectures – Active I/E Converters

Posted on July 7, 2014May 29, 2018 by Dr.Bob

The Classical Potentiostat The schematic at the right is the classical potentiostat design shown in nearly every modern electrochemistry textbook. It has three basic features. The Working electrode is at Virtual Ground. The working electrode is at the same potential as the potentiostat’s electronic ground. This ground is often connected to Earth Ground. The electrometer Read more about Potentiostat Architectures – Active I/E Converters[…]

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

How Fast Can My Potentiostat Scan?

Posted on July 3, 2014June 25, 2015 by Dr.Bob

Several times I have been asked a question about whether potentiostat Model XYZZY can scan at xyz V/s. Rarely is the answer in the data sheet for the instrument. Often, however, enough information is given to assess the limits. The path I follow to arrive at an answer is outlined here. An important fact about Read more about How Fast Can My Potentiostat Scan?[…]

Gamry Interface - Reference Potentiostats

Potentiostat Fundamentals

Posted on June 30, 2014May 29, 2018 by Dr.Bob

Introduction

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

Prerequisites

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.

Electrodes

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 […]

Potentiostat Stability

Posted on June 26, 2014June 25, 2015 by Dr.Bob

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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