http://www.gamry.com/application-notes/EIS/equivalent-circuit-modeling-using-the-gamry-eis300-electrochemical-impedance-spectroscopy-software/

Equivalent Circuit Modeling Using the Gamry EIS300 Electrochemical Impedance Spectroscopy Software

I have successfully used DigiELch.

Thanks a lot !!!

You can also try Autolab Potentiostat

It depends on the file format of your data. If  the format is Zview you can use Zplot software from scribner associates or Ivium potentiostat both are highly recommend. 

Regards

Hi Philipi,

there are different possibilites. I would recommend to use the software that your potentiostat uses.

Nevertheless, you can use Zplot from Scribners:

http://www.scribner.com/software/scribner-associates-software-downloads/160-zplot-and-zview-for-windows-software-downloads

Unfornutately, you need a license to use the full version.

While all these are true, that particular calculation is not really something you need software for (if you don't have it).  On the Nyquist plot go to the peak of the semi-circle, get the value from the real axis, then subtract the uncompensated resistance and multiply by 2.  Better than trying to trace the circle out...I will grant that most people just fit the plot to an equivalent circuit, but if that is all you want it's likely quicker to do it manually.

whatever is the potentiostat/galvanostat  you have used, you can use the software Zview to calculate Rct. Take care you have to take only the part of the nyquist with a semi-circle shape (randles circuit) and avoid the part concerning the warburg impedance.

Thanks a lot to everbody!!! I'll try all this alternatives to calculate the Rct that I need.

Ok, obrigado Leandro Pocrifka. Entrarei em contato com o senhor!

I used EC-Lab software to fit Nyquist curves.