Rotating electrode d.c. solution conductivity device

In an electrochemical cell with one electrode rotating asymmetrically with respect to a second fixed electrode, a constant current produces an a.c. component of the voltage between the pair at the rotational frequency. This a.c. signal arises from the varying iR drop between the extremes of rotational position and thus is a measure of the conductivity of the cell electrolyte. When such a rotating electrode is added to an operating two-electrode cell (e.g. a plating bath), the a.c. signal derived from the rotating element may be used additionally to map the spatial current distribution in the cell. The filtered and amplified signal in either system has also been used to trigger a counter for digital measurement of electrode rotational speed.