AC Wheatsone bridge equivalent impedance at AC

[FvM]

The bridge circuit in post #19 can't be nulled due to phase shift between capacitive and resistive impedance. In so far it's unclear what you want to calculate.

 

[vitoa]

Hi, thank you very much for this simulation. It seems my circuit is not working as I expected. I only have square wave oscillator for this setup.
But I found alternative methood to do good measure of capacitive probe with good results.



Any one could help with the simulation of this circuit?
How can I maximize voltage across AD8307? Oscillator ouputs square wave 3Vpp at 500ohms load

Thanks

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I'm also testing this setup's with good results.



One difference from A to B is probe range. When probe is connected to ground there is no range detection arround probe. But in schematic A probe has detection range about few cm's.
Don't know why this happening, but more range better measure.

 

[BradtheRad]

View attachment 129388

Any one could help with the simulation of this circuit?

I adjusted some values. Current draw is 5-6 mA. The 'R' scope trace shows a response for both C values.



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View attachment 129389

Your latest schematics can be simplified. The righthand one brings out the basic RC time constant. It resembles a schematic you previously posted.

 

[vitoa]

Thanks for simulation. Bridge setup is not the best for this application ,so this circuit will fit better the propouses.