Electrochemical Impedance Spectroscopy (EIS) has become a standard technique in the
electrochemists’ toolbox providing detailed information over very wide time scales and
amplitudes. Commercial instruments are available that can measure impedances from mΩ to
TΩ and over frequencies from μHz to MHz.
Most commonly, EIS is measured using a “single-sine” method where individual frequencies
are measured sequentially. One disadvantage of single-sine EIS is the time it takes to
acquire a full spectrum. A complete sine wave cycle takes ~17 min at 1 mHz and ~27 hrs for
10 μHz. This disadvantage can be overcome by measuring multiple frequencies at the same
time (akin to Fourier transform spectroscopy techniques).
This application note discusses the use of multiple sine wave excitation in EIS and its
implementation in Gamry Instrument software. It does not cover the basics of EIS which are
described in our Basics of Electrochemical Impedance Spectroscopy application note.