A potentiostat is used to set and control the potential of a working electrode. A schematic diagram for a manual potentiostat is shown here where W is the working electrode, A is the auxiliary electrode, R is the reference electrode, SW is a slide-wire resistor, E is a high-impendance potentiometer, and i is an ammeter.
The potential of the working electrode is set relative to a constant-potential reference electrode connected to the working electrode through a high-impedance potentiometer. To set the working electrode’s potential we adjust the slide wire resistor, which also is connected to the auxiliary electrode. If the working electrode’s potential begins to drift, we can adjust the slide wire resistor to return the potential to its initial value. The current flowing between the auxiliary electrode and the working electrode is measured with an ammeter. A modern potentiostat replaces the slide wire resistor with an operational amplifier that automatically maintains the working electrode’s potential; in addition, they often include waveform generators that allow us to apply a time-dependent potential profile, such as a series of potential pulses, to the working electrode
