Patent ID: 7253631

Claim:
A method for determining the complex impedance Z(f m ) of a non-stationary electrochemical system, characterized in that it comprises the steps of: setting the system to a selected voltage state and applying a sinusoidal signal of frequency f m thereto, measuring, immediately after, successive values of the voltage and of the current at regular time intervals ΔT, calculating the discrete Fourier transforms of the voltage (E(f)) and of the current (I(f)), the voltage transform being calculated for the sole frequency f m of the sinusoidal signal and the current transform being calculated for frequency f m and for two adjacent frequencies f m−1 and f m+1 on either side of frequency f m , and calculating the impedance according to the following formula: Z ( f m )= E ( f m )/ I* ( f m ) where I* designates a corrected current such that: Re[I* ( f m )]= Re[I ( f m )]−{ Re[I ( f m+1 )]+ Re[I ( f m−1 )]}/2 Im[I* ( f m )]= Im[I ( f m )]−{ Im[I ( f m+1 )]+Im[ I ( f m−1 )]}/2.