An on-line impedance measuring system based on the fast Fourier transform algorithm was constructed by application of only commercially available interfaces and the FORTRAN language available for an OKITAC System 50/10. A modification of the sampling system is effective for reducing two kinds of errors: the aliasing effect is greatly reduced because of the Nyquist freuency being doubled; the leakage effect is diminished because of the truncation interval being adjusted properly. The above modification enables the authors to acquire high-accuracy data with quite a small number of averagings processed during one measurement, that is, errors may greatly be reduced and the measurement time to get frequency spectra may be made extremely shorter. The modified impedance measurement using the FFT algorithm is applicable to electrochemical systems.
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