Lorentz force magnetometer having a resonator

• US 5,959,452 A
• Filed: 10/03/1997
• Issued: 09/28/1999
• Est. Priority Date: 10/03/1997
• Status: Expired due to Fees

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Givens, Robert B., Kistenmacher, Thomas J., Murphy, John C., Osiander, Robert, Wickenden, Dennis K.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/943,735
• Time in Patent Office: 725 Days
• Field of Search: 324/244, 324/260, 331/65, 331/96, 331/154, 331/155, 331/156, 331/157, 334/4
• US Class Current: 324/260
• CPC Class Codes: G01R 33/028 Electrodynamic magnetometers

Abstract

The invention consists, in one embodiment, of a resonator such as a conductive bar supported by two wires placed at the nodal points of the fundamental resonance frequency. The wires also supply current of this frequency to the resonator. In the presence of a magnetic field, the Lorentz force causes the resonator to vibrate. The amplitude of this vibration is proportional to a vector component of the magnetic field. The motion of the resonator is detected using one of a number of possible methods including optical beam deflection. The invention has a sensitivity of at least 1 nT, comparable to that of a commercial fluxgate magnetometer, and a dynamic range exceeding 80 dB.

Claims

1. A magnetometer comprising:

a resonator containing first and second nodes of fundamental resonance; and

first and second support wires supporting the resonator at the first and second nodes of fundamental resonance for inserting a current at the first node and extracting the current at the second node, the magnetometer being placed in a magnetic field to be detected, the magnetic field being normal to the direction of the current in the plane of the resonator and producing a Lorentz force normal to the resonator, the Lorentz force causing deflection in the resonator that can be detected.

2. The magnetometer as recited in claim 1, wherein the resonator is a bar.

3. The magnetometer as recited in claim 2, wherein the current inserted onto the bar is at the resonant frequency of the bar.

4. The magnetometer as recited in claim 1, further comprising a means for detecting the deflection of the resonator.

5. A method for detecting a vector magnetic field comprising the steps of:

supporting a resonator at first and second nodes of fundamental resonance;

inserting a current at the first node and extracting the current at the second node;

placing the resonator in a magnetic field normal to the direction of the current in the plane of the resonator, thereby producing a Lorentz force normal to the resonator, the Lorentz force causing deflection in the resonator; and

detecting the deflection in the resonator.

6. The method as recited in claim 5, wherein the resonator comprises a bar.

7. The method as recited in claim 6, wherein the current inserted onto the bar is at the resonant frequency of the bar.