Re: gEDA-user: Tool to calculate Nyquist-plot or impedance?

[al davis <ad136@xxxxxxxxxxxxxxxx>]

On Sunday 18 March 2007 17:42, Wen wrote:
> Hi list,
> I am going to do Equivalent circuit fitting for a university
> project with impedance spectroscopy.
>
> I am looking for a tool that first allows  to define (via a
> graphic interface would be best) an electric circuit made of
> resistors, conductors, inductors and maybe constant phase and
> warburg elements.

I had to look up "warburg elements".  Gnucap has constant phase 
elements.  Just specify a complex value for a resistor or 
dependent source.  It looks like it would be easy to make a 
plugin for the warburg elements.  It will be even easier when I 
get the Verilog-AMS compiler working.  For now, you can make 
a "bm" function plugin, using the ones provided as a basis.  
Then a resistor or whatever could have a value that follows the 
warburg function.  Or, you could use the model compiler to make 
a new element, as a plugin.

gnucap plugins allow you to add or replace almost anything at 
run time using the "attach" command.  You write in C++, compile 
to a ".so" and attach it.  To get this functionality you need 
the latest development snapshot.

> What i need is a Nyquist-plot of that 
> circuit-> a plot that shows the imaginary (vert. axis) and
> the real (horiz. axis) part of the impedance of the defined
> circuit for a wide range of frequencies.

Gnucap has impedance probes, so it will give you that directly.  
You can ask for mag&phase, or real&imaginary.  Just ".print ac 
zreal(outnode) zimag(outnode)" or something like that.

You can plot it with octave, gnuplot, R, tcl-tk, or many other 
tools.  gwave doesn't do this kind of plot.


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