Cole impedance extractions from the step-response of a current excited fruit sample

• Presents indirect measurement of single and double dispersion Cole impedance parameters from step response.
• Simple test circuit presented.
• Reduces the hardware requirements by removing need for sinusoidal signal generation and measurement of phase and magnitude.
• Impact of noise on extracted parameter accuracy studied.
• Experimentally validated from the step response using apples as the Cole impedances.

In the field of bioimpedance measurements the Cole impedance model is widely used for characterizing biological tissues and biochemical materials describing the impedance behaviour as a function of frequency. These measurements give information about the electrochemical processes in tissues and can be used to characterize the tissue or monitor for physiological changes. Traditionally these parameters are extracted using fitting routines on direct measurements of the impedance. Here, a method of non-linear least squares fitting (NLSF) is applied to extract the single and double-dispersion Cole impedance parameters from collected current-excited step response datasets without requiring direct impedance measurements. The impedance parameters are extracted from MATLAB simulations showing less than 1% and 5.5% for the single and double dispersion parameters, respectively, when a 0.5% random noise component is present. This extraction is verified experimentally using apples as Cole impedances showing less than 2% relative error between simulated responses (using the extracted impedance parameters) and the experimental results over the entire dataset.