Thanks for the suggestion, Joe.

I'm afraid presets in place of fixed resistors would mean I'd have to calibrate each channel individually; also, I should have mentioned, the capacitor is actually a string of 10 capacitors that get successively shorted by a fluid. So, having unequal fixed resistors in each string would affect the overall linearity.

I intend to try out my 2nd idea, but perhaps with CMOS switches instead of separate mosfets.

Regards,

Anand