7.16) AC impedance/immittance spectroscopy fitting program (LEVM)
Description
This article is from the Electrochemistry FAQ, by Zoltan Nagy nagy@anl.gov with numerous contributions by others.
7.16) AC impedance/immittance spectroscopy fitting program (LEVM)
Program and manual are available for downloading from:
http://www.physics.unc.edu/~macd/
The newest version, V.7.1, allows weighted, complex nonlinear least squares
fitting of some detailed microscopic relaxation models and of millions of
equivalent circuit possibilities.
SOME FEATURES OF CNLS PROGRAM LEVM
Millions of built-in circuit possibilities available. New fitting models
can be easily added since all source code is included
> 10 different weighting choices are available, and weighting parameters
may be free parameters of the fit
> 20 different distributed circuit elements (DCE's) available for circuits
Complex-, real-, or imaginary-part fitting is possible
A complex-fit optimization procedure is available
Input data may be in Z, Y, E (complex epsilon), or M form
Fitting or simulation may be at Z, Y, E, or M level
Input/output may be in rectangular, polar, or log-polar form
Applicable for conductive, dielectric, or mixed systems, including
semiconductors, electrolytes, polymers, etc. Allows simultaneous fitting
of data involving separate conductive-system and dielectric-system
dispersions
Fitting of transient-response data is possible for many response models
Powerful 2- and 3-D plotting program included
Subtraction of the effects of selected circuit elements possible
"Measurement-model" fitting and Kronig-Kramers-type testing available
Estimation of distributions is possible by powerful methods of inversion
of frequency or transient response data. This allows accurate
transformation of wide-range data from time-to-frequency or vice versa
without the need for Fourier transformation
Two types of conductive-system dispersion models available for fitting
Accurate stretched-exponential (KWW) fitting model included
New generalized-exponential-distribution fitting model available
Many of the fitting models may be used with or without adjustable
small-tau cutoff of the distribution of relaxation times (tau) associated
with the response, and the cutoff point may be a free parameter of the fit
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This program is courtesy of J. Ross Macdonald, Department of Physics and
Astronomy, University of North Carolina, Chapel Hill, NC, and Solartron, Inc.
For problems/questions, contact: MACD@EMAIL.UNC.EDU
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