Galvanostat

A galvanostat is a control and measuring device capable to keep constant the current flowing through an electrolytic cell in coulometric titrations, disregarding changes in the load itself. Synonym is "amperostat".

Additional recommended knowledge

Weighing the right way

Daily Sensitivity Test

Safe Weighing Range Ensures Accurate Results

Its main feature is its nearly "infinite" (i.e. extremely high respect to common loads) internal resistance.

The designation "galvanostat" is mainly used in electrochemistry: this device differs from common constant current sources by its ability to supply and measure a wide range of currents (from picoamperes to amperes) of both polarities.

Technical Realization

The simpler galvanostat consists of a high-voltage source producing a constant voltage U with a resistor R_x connected in series: in order to force the flow of an almost constant current through a load, this resistor shall be much higher than the load resistor R_load. As a matter of fact, the current I flowingh through the load is given by

and if R_x>>R_load, the current I is approximately determined by R_x as follows

This simple realization requires rather high voltages (~100 V) to keep the load current constant with sufficient approximation for all practical purposes. Therefore, more complex versions of galvanostats, using electronic amplifiers with feedback and lower voltages, have been developed and produced. This instruments are capable to feed constant currents in the ranges from few picoamperes (pA) to several amperes (A): typical construction for use in the lower range of feed currents uses operational amplifiers.

See also

• Amperostat
• Current source
• Potentiostat

External links

• Pierre R. Roberge (Webmaster) "Galvanostat", corrosion-doctors.org Electrochemistry Dictionary.