Hi,
This Thread describes how to measure the capacitance of a capacitor using only 2 components and an Arduino. The whole thing functions by calculating the capacitance of the capacitor trough measuring the frequency generated by a Schmitt trigger oscillator.
It uses the formula:
f=1/T=1/(KRC)
K… you have to play around with this value to make your measurements accurate. When using a 185k resistor it is about 1.7
R… resistance in Ohms
C… capacitance in Farad
Download and install the library from FreqMeasure Library, for Measuring Frequencies in the 0.1 to 1000 Hz range, or RPM Tachometer Applications
open my attached (dirty) code.
build the circuit shown in the schematic
connect the circuit to the Arduino.
Input Pins to use:
Teensy 3.1: 3
Teensy 3.0: 3
Teensy 2.0:10
Teensy 1.0: 16
Teensy++ 2.0: 17
Teensy++ 1.0: 17
Arduino Uno: 8
Arduino Leonardo: 13
Arduino Mega: 49
Sanguino: 14
Have fun! 
Capacity_measuring.ino (813 Bytes)
