The traditional way to measure impedance using single-sine (monochromatic) excitation is the most transparent and robust way to find reliable EIS data. Compared to the time saving polychromatic (i.e. multi-sine) excitation, the advantage of single-sine excitation is the unequivocal assignment of harmonic content in the response signal to unwanted interference. Systematic analysis of these harmonics allows for the determination of a reliable measurement variance for every single data sample immediately after raw data collection is complete. For decades, such a procedure named “Weighted Harmonics Autocorrelation” has proven its benefit for the EIS instruments of the authors group [1]. Another helpful feature is owed to the periodicity of the monochromatic excitation: unwanted time drift contributions can be calculated from succeeding periods of the response signal for the reconstruction of the drift-free response. This allows for an automatic drift correction [2].

These valuable features are hardly achievable using standard multi sine techniques. Here, even in the absence of interference, the response signals are neither periodic nor free of harmonics. In spite of the fact that monochromatic techniques have the better relationship between information density and time effort [3], it is sometimes preferable to use multi-sine whenever the total measurement time is crucial for practical reasons.

In this poster, a novel multi-sine excitation method will be presented that keeps the advantages of automatic drift correction and online error determination analogous to the monochromatic single-sine procedure.

Keywords: EIS, error determination, drift correction, multi-sine, single-sine

References:

[1] C.-A. Schiller, R. Kaus; Impedance Contributions Online 2008, 6, P4.1 - P4.13 http://accessimpedance.eu/images/stories/ICO6_P4.pdf

[2] C. A. Schiller, F. Richter, E. Gülzow, N. Wagner; J. Phys. Chem. Chem. Phys. 2001, 3, 374-378

[3] Ruben H. Milocco, Minimal measurement time in electrochemical impedance identification, Electrochim. Acta 1994, 39, 1433-1439