Documentation EISfit 1.0.6
Loading data
Data can be loaded in the usual way. At the moment only data saved from the FRA software
from Ecochemie (Version 7 or 8) can be loaded, impedance data from Ivium (e.g.,
CompactStat, software version 1639) or ASCII text files generated by the CH Instrument
software or by software controlling EC-lab potentiostats. Please contact me if you like other
‘ASCII’ files to be included in this list.
View
The program usually shows a graph in the EIS representation you have selected to fit.
However, you can select All graphs if you like four different representations to be shown
simultaneously.
Data to fit
Here you can select which data representation to fit. Of course you always fit the same data,
but the representation dictates how the weighting is performed. For instance in the Nerquist
plot, the weighting of a R(RC) element will be very sensitive to the parallel Resistor element,
and less sensitive to the serial Resistor. You can also select ‘absolute weighting’ or ‘relative
weighting’. In absolute weighting all points are treated the same, but in relative weighting,
data points with lower values will get a higher weighting. Note that in relative weighting,
fitting in Cole-Cole and in Admittance will give the same results as the Cole-Cole
representation is a normalised Admittance plot.
Circuit
In the circuit ‘field’ you can enter a circuit in a line representation. The following elements
are possible:
R - Resistance (1 parameter)
C - Capacitance (1 parameter)
Q - Constant phase element (Z = 1/((iω)αQ)) (2 parameter)
W - Warburg (see http://www.consultrsr.com/resources/eis/index.htm, 1 parameter)
G - Gerischer impedance (see http://www.consultrsr.com/resources/eis/index.htm, 2
parameters)
T - Hyperbolic tangent (see http://www.consultrsr.com/resources/eis/index.htm, 2
parameters)
O - Hyperbolic co-tangent (see http://www.consultrsr.com/resources/eis/index.htm, 2
parameters)
H - Havriliak–Negami function (5 parameters)
Z Cdl =
1
⎡
⎤
ΔC
+ C inf ⎥
⎢
α β
⎣ (1 + (iωτ ) )
⎦
D – Dispersive Capacitance Function (5 parameters)
1
Z Cdl =
⎡ ΔC
⎤
+ C inf ⎥
(iω ) β ω 01− β ⎢
α
⎣1 + (iωτ )
⎦
Note that only circuits can be used that give up to 15 parameters.
Monte Carlo Simulations
Errors can be calculated using a Bootstrap method and Monte Carlo Simulations. If you want
errors to be calculated please fill in the number of Monte Carlo Simulations you want
performed. Usually, between 200-500 simulations are sufficient.
Saving data
The data will be saved in several EIS representations. If a simulation or fit has been
performed the circuit and parameters, as well as the fit, are also saved.