Magnetometer operated at a self-resonant frequency by a sense winding

• US 4,626,782 A
• Filed: 09/26/1983
• Issued: 12/02/1986
• Est. Priority Date: 09/26/1983
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Lewis, Richard W.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US06/535,408
• Time in Patent Office: 1,163 Days
• Field of Search: 324/253-255, 324/260, 324/117 R, 33/361, 340/870.33
• US Class Current: 324/253
• CPC Class Codes: G01R 33/04 using the flux-gate principle

Abstract

A self-resonant magnetometer using the inductance and interwinding capacitance of a sense winding to establish the frequency of operation. A sense winding signal is amplified to provide a driver current for a driver winding. The driver winding current with the addition of a dc offset current causes the mu (permeability) of a ferrite core to vary in a non-linear region of its B/H curve. The change in the mu of the ferrite core produces a change in flux in the magnetic core if an external magnetic field is present. This change in flux induces a signal in the sense winding.

Claims

1. A self resonant magnetometer for effectively measuring an external magnetic field and eliminating ringing noise normally associated with a magnetometer when an external signal is received, the magnetometer comprising:

a ferrite core;

a driver winding wound on the ferrite core for magnetizing the core in its non-linear region near its saturation level;

a voltage source connected to a resistor, the resistor connected to and biasing the driver winding and providing a current which will bring the permeability of the ferrite core near its saturation level;

a sense winding wound over the core and the driver winding, through interwire capacitance inherent in the sense winding the sense winding is designed to operate at a self-resonant frequency, this frequency is the same as the operating frequency of the magnetometer for eliminating noise related therewith;

an operational amplifier having its input connected to the sense winding and its output coupled to a dc blocking capacitor, the capacitor connected to the driver winding; and

an output signal detector via a lead connected to the sense winding for receiving a signal therefrom, the signal proportioned to the external magnetic field sensed by the sense winding;

the sense winding indirectly connected to the driver winding via the amplifer and capacitor, any additional current, as sensed by the sense winding due to the external field, is amplified by the amplifier to the capacitor to the driver winding for driving the core into its non-linear region near saturation thereby changing the permeability rapidly and at the same time the sense winding providing the output signal during the permeability change.

2. The magnetometer as described in claim 1 wherein the ferrite core is a toroidal core with the driver winding wound thereon.