You can model impedance spectra various equivalent circuits. For example, a spectrum displaying two time constants can be modeled by a number of different equivalent circuits. You cannot assume that… read more →
Modern EIS analysis uses a computer to find the model parameters that give the best agreement between a model’s impedance spectrum and a measured spectrum. A non-linear least squares fitting… read more →
The impedance behavior of a purely capacitive coating was discussed in Model 1. Most coatings degrade with time, resulting in more complex behavior. After a certain amount of time, water… read more →
EIS data are generally analyzed in terms of an equivalent-circuit model. The analyst tries to find a model whose impedance matches the measured data. The type of electrical components in… read more →
A metal covered with an undamaged coating generally has a very high impedance. The equivalent circuit for a scenario like this includes a resistor (primarily caused by the electrolyte) and… read more →
The Randles cell is one of the simplest and most common cell models. It includes a solution resistance, a double-layer capacitor and a charge-transfer or polarization resistance. In addition to… read more →
First consider a cell where semi-infinite diffusion is the rate-determining step, with a series solution resistance as the only other cell impedance. A Nyquist plot for this cell is shown… read more →
In the following help sessions we show some common models for equivalent circuits. These models can be used to interpret simple EIS data. Many of these models have been included… read more →
The equivalent-circuit elements that can be used in the Modeler are shown below. Equations for both the admittance and impedance are given for each element. Symbol Circuit Element (alphabetical symbol)… read more →
Solution resistance is often a significant factor in the impedance of an electrochemical cell. A modern three-electrode potentiostat compensates for the solution resistance between the counter and reference electrodes. However,… read more →