A Low-Noise Contact for Rotating Electrodes

A contact method for providing a constant, low-resistance connection to rotating electrodes is discussed. It is based upon the use of a consistent, solid/liquid contact between a stationary copper wire and a small mercury pool which rotates with the electrode. The des.ign is shown to reduce the noise of electrochemical data. This is particularly important for experiments on oscillations and chaos in which analysis methods from nonlinear dynamics are employed. A second advantage of this design compared to a silver-carbon brush is that there is less change or drift in the measured signal during a long-term experiment. Rotating electrodes have been used for many years in electro-chemical studies due to the well-defined hydrodynamics, ease of construction, and large mass-transport egime that can be explored with them. 13 Electrical contact to the rotating specimen is usually made via a spring-loaded, silver-carbon brush which provides a low-friction, low-resistance contact. 2However, this contact method can lead to noise in the measured current due to slight inhomo-geneities in the contacting surfaces and their evolution during the experiment. This is particularly true at high rotation rate