Capacitance meter using the Photon

[rocksetta]

@peekay123

should add a unity gain op-amp buffer! This will provide the impedance isolation needed

Looking how to do that. Finding info here:

Sudden Photon Death

That will work, assuming your sensor can drive some current! The resistors can be much higher in resistance, particularly if you’re using a unity gain op-amp buffer. And my bad for not thinking ahead quite far enough. I understand the concern about loss of resolution; you probably could get away with a series resistor and a switching diode (i.e. 1N914–or pretty much anything!) to the 3.3v rail. (And one to the ground rail, just to be safe!) Basically, you’re trying to ensure that a spike o…

and here:

https://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/OpAmps/OpAmp3Note1Buffer.html

So the basic circuit looks fairly easy

https://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/OpAmps/OpAmp3A01.gif

Using @Ric slightly changed Capacitor test circuit where would this unity gain op-amp buffer go and what chip would you suggest if it isn't just a simple transistor.