A device used to provide a steady adjustable current between two electrodes. The device will vary the potential between the electrodes in such a way as to keep the current constant, as long as the operating tolerance of the machine isn't exceeded. This may be required if the resistance of the conducting medium between the electrodes varies with time. Because the potential drop across the electrodes relates current to resistance, an increased resistance must be offset by an increased potential in order for the current to remain constant1.
Galvanostats derive their name from Luigi Galvani (1737-1798), who made discoveries involving electricity and biological tissue.
These devices are used today in electrochemical cells in order to mediate chemical reactions which are facilitated by electricity, for example electrochemical etching. The yield and rates of some chemical reactions are goverened by the current flowing between electrodes, making galvanostats important in such applications. These machines are often programmable and may be computer controlled, allowing the user to precisely adjust the current over time, providing such functions as ramps and saw-tooth patterns, depending on application. Many galvanostats double as potentiostats, allowing precise control of electrode potential by instead varying current.
- vuo graciously points out that Ohm's Law doesn't hold for chemical solutions in all but limiting cases, since free charge carriers are not in abundant supply as with metals.