Harmonic distortion caused by electrode polarisation.

Steady-state measurements of the electrical properties of electrodes immersed in physiological saline were taken with small- and large-amplitude sinusoidal voltages (30 m V-1 V) in the frequency range 0.2 mHz-2 Hz. Impedance magnitude and phase, and the first four Fourier series coefficients of the polarised current were measured. The dependence of the polarisation admittance on input current intensity was modelled with the linear relationship proposed by Schwan. This model predicts harmonics in the non-linear range for AC overpotentials up to several hundred millivolts. Observed values deviated from theoretical values. Reasons for such deviations are discussed. The study of harmonic distortion appears to be a useful tool to monitor and predict the non-linear behaviour of the interface and other dielectric phenomena.