Rotating machine component clearance sensing systems and methods

A method for measuring a clearance of a rotating machine component, the method comprising:

• providing a sensor oriented to detect the rotating machine component as the rotating machine component rotates past the sensor, the sensor comprising:
• a split pole piece that comprises a leading pole on a first leg of the split pole piece and a trailing pole on a second leg of the split pole piece, such that the leading pole is spaced apart from the trailing pole in a direction of rotation of the rotating machine component, wherein the split pole piece comprises a base that extends between and connects together the first and second legs;
• a first sensing element, which comprises the leading pole and a leading sensing coil extending around the leading pole;
• and
• a second sensing element, which comprises the trailing pole and a trailing sensing coil extending around the trailing pole;
• and
• a permanent magnet;
• wherein the first leg of the split pole piece comprises ferrous material and is configured to direct magnetic flux of the permanent magnet along a length of the first leg;
• and
• wherein the second leg of the split pole piece comprises ferrous material and is configured to direct magnetic flux of the permanent magnet along a length of the second leg;
• and
• receiving a first waveform from the first sensing element;
• receiving a second waveform from the second sensing element;
• determining, using a sensor processor in electrical communication with the sensor to compare the first waveform and the second waveform, a distance between the rotating machine component and the sensor.

A system for measuring a clearance of a rotating machine component, the system comprising:

• a sensor oriented to detect the rotating machine component as the rotating machine component rotates past the sensor, the sensor comprising:
• a first sensing element that comprises a first pole piece, a first sensing coil wrapped around a first end of the first pole piece, and a first permanent magnet at a second end of the first pole piece, the first and second ends of the first pole piece being opposite each other;
• and
• a second sensing element that comprises a second pole piece, a second sensing coil wrapped around a first end of the second pole piece, and a second permanent magnet at a second end of the second pole piece, the first and second ends of the second pole piece being opposite each other;
• wherein the first sensing element is spaced apart from the second sensing element in a direction of rotation of the rotating machine;
• wherein the first pole piece comprises ferrous material and is configured to direct magnetic flux of the first permanent magnet along a length of the first pole piece;
• wherein the second pole piece comprises ferrous material and is configured to direct magnetic flux of the second permanent magnet along a length of the second pole piece;
• and
• a sensor processor in electrical communication with the sensor and configured for:
• receiving a first waveform from the first sensing element;
• receiving a second waveform from the second sensing element;
• and
• determining, based on a comparison between the first waveform and the second waveform, a distance between the rotating machine component and the sensor.