Patent ID: 7570066

Claim:
An apparatus for simultaneously detecting in-plane and out-of-plane position displacement of a capacitive sensor in a data storage device, comprising: a capacitive sensor having a first electrode connected to a first AC supply voltage operating at a first frequency; a second electrode connected to a second AC supply voltage operating at the first frequency, wherein each of the first and second supply voltages includes an in-phase component and a quadrature component, and a third electrode; a sensing circuit for producing a sense voltage in response to current flowing between the first electrode and the third electrode, and between the second electrode and the third electrode; a first mixer for combining the sense voltage with a first AC reference voltage to produce a first signal representative of in-plane displacement of the first and second electrodes with respect to the third electrode of the capacitive sensor; and a second mixer for combining the sense voltage with a second AC reference voltage to produce a second signal representative of out-of-plane displacement of the first and second electrodes with respect to the third electrode of the capacitive sensor in the data storage device.