Reply to Comments on the Article 'An Electrochemical Impedance MeasurementTechniques Employing Fourier Transform'

摘要

In his comments on our newly developed impedance measurement technique using Fourier Transform, Lasia states that the technique does not contain any information in a low-frequency region, because it is obtained from an extrapolation of the data obtained up to (n_(0)+1)Δt, where n_(0)+1 is the number of points sampled, and Δt is the sampling time. This is not true, because the technique is based on a principle in which a Dirac δ function, which is composed of AC voltages of all of frequenies ranging from infinitely high to infinitely low frequencies (almost dc level) of the same magnitude and phase, is applied to the electrode/electrolyte interface as an excitation source, and the response current resulting thereof is detected and decomposed back into each frequency component by means of Fourier transform (FT). It is similar to a concept used in today's spectrophotometers in which a white light source is used for a sample, followed by decomposing the response signal into each wavelength component using a grating, and detecting them with a photodiode array or a charge-coupled detector. In our measurements, however, an integrated form of the Dirac δ function is applied instead, and the derivative current signal is obtained before decomposing it into each AC current component, because it is very difficult to generate and directly apply the Dirac δ function by known electronic circuits. In doing so, we took advantage of another theorem, which states that for a linear system responding with a function y for an input function x, an input of an integrated or derivative form of the function x gives a response function of integrated or derivative form of y.