AC impedance of a dipole

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Anthony Lethuillier

Anthony Lethuillier

December 3, 2013 1:02pm UTC

AC impedance of a dipole

Hello,

I am at the moment trying to simulate a simple system and I am having a few problems.

I am trying to calculate the self impedance of a dipole located inside a full space of conductivity 0 and permittivity 80.

The dipole is composed of two electrodes represented by two spheres, one is at a potential of 1V and the other is set at the ground. I put the spheres in a rectangle representing the full space.

I would like to plot the self impedance of the dipole as a function of frequency. The self impedance can be expressed as :

Z = (Vt2 - Vt1)/i

Where Vt2 and Vt1 are the potential of the two electrodes and i is the current fed to an electrode. I do a study with in frequency domain : range(1,10,1000).

I then attempt to plot a 1D plot -> Global with frequency in x axis and impedance in y axis.

I do not know what to put in the expression for the Y axis, indeed i would like to plot the formula above but I am unable to find how to express Vt1, Vt2 and i. Is it possible ?

Is there a way to plot directly the self impedance of the dipole with Comsol ?

Thank you very much for your help

Anthony

Attachments:   permittivity_only_2D_test.mph  

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Edgar J. Kaiser

Edgar J. Kaiser
Certified Consultant
emPhys Physical Technology

December 3, 2013 3:26pm UTC in response to Anthony Lethuillier

Re: AC impedance of a dipole


Anthony,

one way to measure the current is to use terminal BC and a circuit physics node that connects to the terminals.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com

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Anthony Lethuillier

Anthony Lethuillier

December 4, 2013 10:05am UTC in response to Edgar J. Kaiser

Re: AC impedance of a dipole

Hello following your advice I made a few changes to the model :

- I put a Terminal at the receiving electrodes (Electric Currents -> Terminal 1 -> I0 = 1A)
- I put an electric potential on the transmitting electrode (Electric Currents -> Electric Potential 1 -> V0 = 1V)
- I put the boundaries of the rectangle at the ground potential as the condition at infinity.

I then complete the study and try to plot the impedance (ec.Z11) as a function of frequency. The plot gives me a constant Impedance not varying depending on frequency (which is unexpected) . I feel I am still doing something wrong.

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Edgar J. Kaiser

Edgar J. Kaiser
Certified Consultant
emPhys Physical Technology

December 4, 2013 11:30am UTC in response to Anthony Lethuillier

Re: AC impedance of a dipole


Anthony,

the reference impedance is a predefined value. That's not what you need. Look at some examples using circuit physics. Search on the forum and the knowledge base.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com

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