| Popis: |
Summary A study is presented of faradaic admittance versus frequency measurements based on Fourier analysis of the response to multiple-frequency test signal waveforms. The waveform types employed encompass both the discrete frequency and broadband categories, including stochastic and deterministic examples of the latter. More specifically, data are acquired using: (a) complex periodic signals; (b) almost periodic signals; (c) transient inputs; and (d) bandwidth-limited white noise. Data analysis is based on the highly-efficient fast Fourier transform algorithm which is implemented by an on-line minicomputer. An instrumental configuration is described which yields valid faradaic admittance data, regardless of the type of test signal waveform employed. Results are examined with regard to the effect of test signal properties on measurement efficiency, where measurement efficiency is defined in terms of the data dispersion observed after a particular number of replicate measurements. In this context the data show that a complex periodic waveform composed of a fundamental harmonic and a sufficient number of odd harmonics is superior to the others which were examined. This result, together with the overall empirical ordering of waveform types versus measurement efficiency, is rationalized in terms of the influences of extraneous noise, faradaic non-linearity, waveform frequency spectrum, and special measurement system characteristics. |
