System and method for disk drive fly height measurement

A system for determining a fly height, comprising:

• a first head of a disk drive, the first head being adjacent to a first disk;
• a capacitive fly height sensor circuit coupled to the first head, wherein the capacitive fly height sensor circuit is configured to measure a first capacitance between the first head and the first disk;
• a second head of the disk drive, the second head being adjacent to a second disk;
• a reference capacitive sensor circuit coupled to the second head, wherein the reference capacitive sensor circuit is configured to measure a second capacitance between the first head and the first disk;
• and
• a logic device, the logic device being coupled to the capacitive fly height sensor circuit and the reference capacitive sensor circuit, wherein the logic device is configured to:
• remove noise to correct a measurement of the capacitive fly height sensor circuit using a measurement of the reference capacitive sensor circuit;
• and
• determine the fly height between the first head and the first disk using the corrected measurement of the capacitive fly height sensor circuit.

A method for operating a disk drive, the method comprising:

• selecting a first head for an operation on a first disk;
• moving the first head closer to the first disk;
• measuring a first capacitance between the first head and the first disk;
• correcting the measurement of the first capacitance using a second capacitance as a reference, the second capacitance being between a second head and a second disk;
• adjusting a fly height of the first head using the corrected measurement of the first capacitance;
• and
• performing the operation on the first disk with the first head.