Schematic for capacimeter project

Sorry, only down Argentine way.

I have an interest in this area to to measure anodized layer thickness. Guessing at Techniques.....

1) RC voltage divider driven by an audio oscillator. 2) Ctest is part of an LC oscillator, phase shift or hysteresis oscillator. 3) Constant Iout. Time is measured to determine Ctest. 4) C measurement chip?? 5) Maybe some method of phase measurement

I'd probably go for the voltage divider technique.. D from BC

Well, there's lots of ways to do that. Simple way #1, just connect line current (this presumes constant power voltage) to one side of the capacitor, and rectify the current through the capacitor and run it through a moving-needle meter movement.

This only requires two diodes, a meter, and a known AC source. Downside: high voltages blow up some capacitors, and other capacitors will blow up your meter movement. Also, don't touch it with the power on!

Better solutions require other (safer) AC sources, and use amplifiers with range settings.

For practical purposes, digital C-meters are easy to build; it turns out that the usual voltmeter (dual-slope converter) operates in two phases, first charging a capacitor with an unknown, then timing the discharge with an accurate known discharge current source. If you give the capacitor a known voltage in the first phase, the discharge time (and thus the digital readout) is proportional to the capacitor value.