From help-request at octave dot org Mon Dec 20 09:35:00 2004 Subject: invfreqs and Warburg impedance From: "Pascal A. Dupuis" To: help at octave dot org Date: Mon, 20 Dec 2004 09:22:57 -0600 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 ) 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 -------------------------------------------------------------