From help-request at octave dot org Tue Dec 21 05:37:43 2004 Subject: RE: invfreqs and Warburg impedance - use LEVM From: "Harbinson, Jeremy" To: Cc: "Pascal A. Dupuis" Date: Tue, 21 Dec 2004 12:39:04 +0100 Hi, There is free fitting and simulation package for bioimpedance and other = specialised impedance application. This has pre-built models for various = CPEs such as Cole-Cole, Havriliak-Negami, Warburg etc. The package is a = little bit awkward to use - you will need to read the manual carefully, = but the package does work nicely once you have got to know it. You can = download it from the Solartron web site http://www.solartronanalytical.com/downloads/software.html All the best, Jeremy Harbinson -----Original Message----- From: Pascal A. Dupuis [mailto:Pascal dot Dupuis at esat dot kuleuven dot ac dot be]=20 Sent: maandag 20 december 2004 16:23 To: help at octave dot org Subject: invfreqs and Warburg impedance Hello, I'm trying to describe an Impedance measured over a few frequencies = points as a combination of resistors/capacitors, using the invfreqs = function. But the underlying system is comprised of a pair of = electrodes, and some biological medium, so the impedance contains a = so-called Warburg element, that is, a capacitor in parallel with a = resistor, where the phase angle is constant (45 =81=B0) and the product = of R and C is equal to 1/f. When I plot the impedance locus (real part, imaginary part), it is = obvious that there is something going wrong with the approximation using = constant R and C. Did someone already coped with this, coming to some = iterative method permitting to extract the Warburg element and = progressively come to a good approximation of the measured impedance. TIA Pascal Dupuis -- Dr. ir. Pascal Dupuis K. U. Leuven, ESAT/ELECTA (formerly ELEN): = http://www.esat.kuleuven.ac.be/ Kasteelpark Arenberg, 10; B-3001 = Leuven-Heverlee, Belgium Tel. +32-16-32 10 21 -- Fax +32-16-32 19 85 ------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html ------------------------------------------------------------- ------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html -------------------------------------------------------------