Hi everyone,

I am working on a part of my project that is essentially a capacitance meter. So far it works well for capacitances from 2 nano Farads upwards.

I have a 10 M Ohm resistor in series with the unknown capacitor and the code measures the time taken for the voltage across the capacitor to reach 63% of its final value.

This is the RC time constant, and is equal to RC, from which C can then be determined.

However, I need it to go down to measure values lower that a few nano Farads. Ideally it needs to be able to measure a capacitance of a few pico Farads.

Of course at the moment the RC time constant would be undetectable (a few nano seconds). So I would need to either increase the resistance, or find a new way to measure.

Is increasing the resistance into the Giga-Ohm range viable?

If not, does any one have any suggestions of how to measure small values of capacitance using Arduino microcontrollers?

Thanks guys, would appreciate any help.