B. Impedance and Dissipated Power Characteristics
We determine the impedance characteristics of an electrode
at various voltage levels by plotting V versus I, both of which
are sampled periodically with a digital oscilloscope. From these
data, we determine the average total impedance modulus during
the phase when both current and voltage have stabilized (transients during times when either voltage or current are varying
rapidly are ascribed to capacitive effects and ignored). In Table I,
we tabulate various parameters for a multielectrode probe at various voltages, in addition to the power dissipated computed by
multiplying the instantaneous voltage and current and averaging
over a complete cycle. In Fig. 5, we show the impedance versus
voltage for a 0.9% NaCl saline solution (isotonic saline). At
low voltage, the impedance is rather low and has a slight positive slope. The increasing impedance as the voltage increases
is rather significant. The conductivity of most saline solutions,