This circuit was originally designed to measure the volume of fluid inside a
medical syringe. As designed, it produces a zero to 5 volt output,
corresponding to a capacitance change of about 10 picofarads. With a digital
voltmeter, at its output, it can resolve a capacitance change of 0.002 picofarads
or 2 femtofarads.
Click on Drawing Below to view PDF version of Schematic