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schematic

simulate this circuit – Schematic created using CircuitLab

I am using several analog multiplexers to switch signals from a potentiostat to various electrodes. I am powering the MUXs with 0V and 5V and the impedance spectroscopy output from the potentiostat signal sits at 1.6 V +/- 10 mV. I need to make it so that the electrodes don't float significantly far from the signal so I would like to fix the open MUX outputs to the same voltage as the potentiostat.

Is there a good way to do this? An idea I have is to extract the potentiostat signal (Vref) using a sample and hold circuit, and then using a bunch of 1:1 MUX to short Vref to the open outputs. Then I could use decoders to close all the 1:1 MUX channels except for the currently active electrode that is being measured by the potentiostat.

An issue I foresee with this method is that if Vref changes, my electrode potentials will change which could affect the measured results. I am open to tips or better ideas of how to go about this.

Edit:

I added a schematic of my idea. Importantly the electrodes are patterned on a chip that sits in an electrolyte, so there is no electrical connection between them.

I am currently using a MAX396 16:1 MUX because it has fairly low channel capacitances and moderate on resistance. I need to make sure I don't have excess parasitic capacitance or else I will be unable to take impedance measurements. The on resistance is less important for my application, but lower is better.

I just started looking at 1:1 analog switches, so I don't know what component I would use. I'm sure I need something with very low leakage current though.

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    \$\begingroup\$ This all sounds a bit wrong to me so, to clear this up draw a schematic proposal. \$\endgroup\$ Commented Oct 24 at 20:35
  • \$\begingroup\$ yeah, there's multiple "no that can't be right" as I read your question. Without a schematic, there's too much guessing what you really mean. Please add a schematic to your question, make sure to name your parts, and clearly mark the parts that you want to float or not float, specifically. You should probably also explain why you chose the type of MUX you chose! (there's many different muxes with different io characteristics, and I'd guess that matters here, a lot) \$\endgroup\$ Commented Oct 24 at 21:33
  • \$\begingroup\$ I made a schematic and described the 16:1 MUX I am currently using. Please let me know if anything is unclear (or if this idea just won't work). \$\endgroup\$ Commented Oct 24 at 22:47
  • \$\begingroup\$ Do you measure AC or DC impedance? How is this done? \$\endgroup\$ Commented Oct 24 at 23:18
  • \$\begingroup\$ I use a potentiostat to run an Electrochemical Impedance Spectroscopy measurement from 10 Hz to 100 kHz using V_DC at 0 V vs the reference (which is about 1.6 V vs. ground) and a 10 mV V_AC signal \$\endgroup\$ Commented Oct 24 at 23:30

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