Potentiostatic frequency response analyser

Fig.II.5.1 Block diagram of a potentiostatic frequency response analyser...

AC impedance measurements were also made in bulk paints. A Model 1174 Solartron Frequency Response Analyser (FRA) with a Thompson potentiostat developed ac impedance data between 10 KHz and 0.1 Hz at the controlled corrosion potential The circuit has been described in the literature( ). 

Many applications of this strategy are based on extensions of the concepts of impedance developed earlier in this chapter (41-43). However, the excitation waveform is usually an impulse in potential (rather than a periodic perturbation), and a transient current is measured. One records both E t) and i t) as observed functions. Then both are subjected to transformations, and comparisons are made in the frequency domain between E s) and i s). Ratios of the form i s)IE s) are transient impedances, which can be interpreted in terms of equivalent circuits in exactly the fashion we have come to understand. The advantages of this approach are (a) that the analysis of data is often simpler in the frequency domain, (b) that the multiplex advantage applies, and (c) the waveform E(f) does not have to be ideal or even precisely predictable. The last point is especially useful in high-frequency regions, where potentiostat response is far from perfect. Laplace domain analyses have been carried out for frequency components above 10 MHz. 

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