Electron Tunneling Magnetic Field Sensor with Constant Tunneling Current Maintained Between Tunneling Tip and Rotatable Magnet.
Patent, Filed 7 Feb 94, patented 2 Jan 96,
DEPARTMENT OF THE NAVY WASHINGTON DC
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The magnetic sensor of this invention is characterized by a magnet suspended on a torsion bar or wire and by a tunneling tip separated from one end of the magnet, a gap between the tip and the magnet that is small enough to support a tunneling current, an electrical source for imposing a constant biasing voltage across the gap, an electrical force to maintain the magnet and the tip sufficiently close so that a constant tunneling current is maintained therebetween, a feedback circuit to monitor current changes in the gap that result from rotation of the magnet due to changes in the surrounding magnetic field and at least one recorder to record changes in the magnetic field. The method for detecting rotation of a magnet by a sensor caused by a change in the surrounding magnetic field includes the steps of biasing tunneling tip and a magnet with respect to each other, positioning the tip andor magnet so there is a tunneling current therebetween, adjusting width of the tunneling gap to establish a constant tunneling current therebetween, exposing the magnet to a magnetic field that causes the magnet to rotate and to change the width of the gap, adjusting the width of the gap to reestablish a constant tunneling current in the gap, and recording the change in the feedback control voltage which is proportional to the change in the magnetic field.
- Magnetic and Electric Field Detection and Detectors