US Patent 7710205 Capacitor detection by phase shift

A method and apparatus for detecting capacitive devices are disclosed. A circuit including two circuit paths is connected to an oscillator voltage source. Connecting a test capacitive device to a path of the circuit modifies the electric potential waveform at a point along the path. Passing the first circuit path through a reference comparator and the second circuit path through a phase-shifting comparator produces two output signals that are phase-shifted with respect to each other when the test capacitive device is functional. Analysis of the output signals allows detection or measurement of the test capacitive device.