Potentiostats and galvanostats are electrochemical instruments used in electrochemistry, battery and fuel cell testing, corrosion control, voltammetry, biomedical research, surface imaging, and related applications. Potentiostats are used to keep the potential (voltage) between a working electrode and a reference electrode at a constant value. Galvanostats are used to maintain a constant flow of current through an electrolytic cell. With potentiostats, the signal from the reference electrode is fed through an impedance transformer which amplifies the input current, but leaves the voltage unchanged. An input resistor protects the buffer from static loads, and a capacitor reduces the intrinsic noise. Like potentiostats, galvanostats function as electronic amplifiers with low feedback. A simple galvanostat produces a constant voltage with a resistor connected in series. To force the flow of a near-constant current through a load, this resistor needs to function at considerably higher levels than the load resistor. A more complex galvanostat can feed a constant current ranging from a few picoamperes (pA) to several amperes (A).
Selecting potentiostats and galvanostats requires an analysis of product specifications and features. Key parameters include maximum current, maximum voltage, current resolution, capacitance, and input impedance. Additional considerations include interface type, number of inputs per channel, and average sampling time. Some potentiometers and galvanometers include low-current and high-current options. Others feature automatic current ranging, simultaneous measurements of voltage and current, and booster options. Single-channel potentiostats and galvanostats are designed for applications such as basic electrochemical research. Multiple-channel products are complete electrochemical workstations that are suitable for electrochemical impedance spectroscopy (EIS) and square-wave voltammetry. With a multi-channel potentiometer or galvanometer, each channel can operate independently or on a synchronized basis. Rotating electrode control is available with some potentiostats.
Potentiostats and galvanostats differ in terms of form factor and may include integral software that runs under the Microsoft Windows operating system (OS). Both Microsoft and Windows are registered trademarks of Microsoft. Software features may include cyclic and linear voltammetry, normal and differential pulse voltammetry, user-definable programming, and chronoamperometry and chronopotentiometry. Potentiostat software with potentiostatic polarization, galvanostatic polarization, and potentiodynamic polarization is also available. Galvanostat software may provide linear polarization resistance (LPR) and zero resistance ammetry (ZRA).