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I need to design a flow-through cell but I don't know how to calculate the cell constant for such a cell. It needs to have 2 ring electrodes within an insulating tube (see pic below). One of the electrodes will have a voltage applied while the other will measure the current. I know that the cell constant for a parallel plate cell is L/A while the cell constant for a concentric cylinder cell is ln(r2/r1)/2(pi)L as explained in another forum post: How to calculate resistivity from this cell design?. I think it's difficult to calculate the cell constant for the flow-through case as all parts of the surfaces of the electrodes will not be the same distance apart. I would appreciate any help.

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J. Doe
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  • This might be better suited for the physics stack exchange. – DKNguyen Apr 13 '20 at 15:14
  • The highest rated answer (not the selected one) is that "you don't, you calibrate it with a standard solution". My second choice would be to do it numerically with a finite element analysis (assuming this is a real problem and not a homework assignment). – Spehro Pefhany Apr 13 '20 at 15:26
  • @SpehroPefhany Hi, this is not a homework assignment, it's a project for my phd. I need to first design it before i can construct it and calibrate it. It's best to first have a theoretical approximation of the cell constant so i can design it. I was wondering if you explain how i would go about solving this numerically with FEA? thank you. – J. Doe Apr 13 '20 at 15:36
  • Do you have access to something like Comsol or ANSYS? I mean you could do it from scratch (I did back in University), but there are modern tools available now. – Spehro Pefhany Apr 13 '20 at 15:39
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    @SpehroPefhany Yh i have comsol. I didn't know you could use it to do this though. Thank you. – J. Doe Apr 13 '20 at 15:44
  • A general note- it would be nice sometimes if people filled in at least a bit of their profile, makes it easier many times to tailor a response. – Spehro Pefhany Apr 13 '20 at 15:46

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Here is a webinar on using Comsol to model electrochemical systems.

I think in practice you'll get close making some simplifying assumptions and then calibrate it with a reference solution.

I did some commercial conductivity instrumentation for RO systems used in hospital medical dialysis installations, and the conductivity cell response has some 'interesting' dependencies on both measuring voltage and frequency.

Spehro Pefhany
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