EIS is foremost a measurement technique and not a modeling technique. A stimulus is applied and a response measured. Each response can be described with three variables, either CRn or LRn.
- Using a Gaussian equation fit parameters can be displayed as a line graph of multiple peaks in Bode form.
- As a separate exercise, values of the fit parameters are used to support a physical model of the system.
- The approach is applicable to both high and low impedance applications.
The Bode Plot below is a single response, ECM, in series with an inductor. The right Log y-axis can be used for both capacitance and inductance (mirrored by using the absolute values). The left y-axis is the ratio of Zimag/Zreal (dashed line), emphasising impedance dominance along a current path rather than more obscure phase angle, ArcTan(Zimag/Zreal). Impedance curves are Zimag in blue, Zreal in red, Zmag is green. The different portions of the curve are identified by the annotations.
The y-axis of the Bode plot can also be changed to line graph ‘SpecView’ presentation using a Gaussian equation. This allows graphic overlaying multiple data sets. The Gaussian peak height can represent either capacitance (left) or thickness, d =ee*A/C, (right) , peak position as either Log Frequency (left) or Log Resistance (right), and peak width is proportional to the power law parameter n. Below are shown results for high impedance anodic films on Zirconium.
