Fractional-Order Equivalent Circuit Representation of Kohlrabi Tissue Samples

In an effort to investigate the electrical impedance properties of kohlrabi (Brassica oleracea var. gongylodes L.) plants, the range/variability of kohlrabi impedance from a collection of 16 similarly sized samples were explored. The impedance data was collected in a bipolar configuration interfacing copper wires into discs of sliced kohlrabi plants. An optimization algorithm was used to fit the collected data to a fractional-order equivalent circuit model. The model used to represent the approximated data consisted of a fractional-order capacitor in series with a parallel CPE-R. The electrical impedance of all samples represented by this model had less than 10% deviation in the band from 40 Hz to 1 MHz. Despite having similar dimensions and electrode configurations (material, insertion depth, spacing), there was a high variability (up to 70%) between fractional-order model parameters of the samples.