Four Electrode Method for Impedacne measurement

Hello~

I'm complete a new for COMSOL, but I have to use this for simulation.

Right now I am trying to measure the impedance of the object with 4 electrode method.

I used AC/DC module, Electric Current.

Basically I made 2 separate regions that have different conductivity.

and Put 4 small lines (electrodes), and make one of them terminal of current and one of them ground.

there is a option that I can find the impedance based on the current I put on the terminal

but I want to measure the voltage on other two electrode and measure impedance between them.

NOT the electrode I assigned as the terminal and ground.

I'm attaching the file I'm working on. there are 4 small line on the middle of the object and the two of them on the middle

have not been assigned anything.

Please help me to solve this problem. I really need to figure out this.

One more thing, is this possible to do the same thing in 3D mode? I think I have to improve this simulation in 3D later.

*** now I have file size error.. can't upload file.. what should I do..
I upload the spectrum picture to give basic Idea for what I'm doing..