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In this study, electrode contact impedances and their effects on the measurement have been studied
in a fruit impedance measurement system using Electrical Impedance Spectroscopy (EIS). The EIS study has
been conducted on the banana samples during their ripening and the variation of contact impedance with
frequency at different ripening state has been observed. The contact impedance under each electrode has been
calculated by using compound electrodes developed from stainless steel sheets and the effect of the contact
impedance on the measurement accuracy has been studied. The total contact impedance has been computed
by comparing electrical impedance of banana obtained with two terminal and four terminal method using the
compound electrodes consisting of current and voltage electrodes concentrically placed on banana surface.
It is found that banana impedance obtained with two terminal method is higher in magnitude than the four
terminal method with compound electrodes. It is also found that the contact impedance under each electrode
is maximum at low frequency and minimum at high frequency.
