Any study of the electrical properties of electrodeelectrolyte systems is rendered difficult by their
dependance on, amongst other things, electrode history,
electrode surface finish, electrode geometry, electrode
area, electrolyte composition and the frequency and
amplitude of the applied signal.
Distinguished scientists in this field have recently
concluded that "there appears to be, so far, no model
available which would account for both the linear and
non-linear behaviour of the electrodes in the frequency
and time domain" (Fischler and Schwan, 1981).
Such a model has, however, been developed in this
thesis, which, it is believed, successfully interprets
and models the wealth of empirical observations
reported in the literature.
The source of the observed frequency dependence of the
inter-electrode impedance is traced to the electrodeelectrolyte interface impedance and is approximated by a "constant phase angle impedance", ZCpA. It is established that the form of this impedance is largely
due to electrode surface effects and to a lesser degree
by those of specific adsorption.
It is demonstrated that the observed non-linearities of
the electrode system are largely due to a charge
transfer "resistance", RCT, which shunts ZcpA .
Empirical expressions of the system's non-linearity
found in the literature are physically interpreted and
similar expressions are derived based on the model.
The changes in inter-electrode impedance due to
electrode failures are investigated, modelled and
interpreted. Such alterations in loading are found to
give rise to changes in pacemaker output and current
response waveform. For certain pacers these externally
observable parameters can enable the detection and
classification of electrode failure, sometimes in a
latent stage before failure to pace.