Method and circuit for compensating barkhausen signal measurements in magnetic materials having a variable geometry

Claim 2

In a system for deriving and displaying the Barkhausen signal generated within a body of magnetic material responsive to a variable magnetic field having an electromagnet, a power source connected to the electromagnet for passing a time-varying current therethrough, detecting means within the magnetic field created by the electromagnet adapted for response to Barkhausen noise, and signal processing means connected to the detecting means for deriving a useful Barkhausen signal, the improvement comprising magnetic flux density detecting means for detecting the magnetic flux density of the body in the area of the Barkhausen noise measurement and generating a signal representative thereof, and gain control means for receiving said magnetic flux density signal and controlling the gain of the power source for controlling the time-varying current applied to the electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent the magnetic flux density detecting means at predetermined value for reducing variations in the measured Barkhausen signal due to the geometry of the magnetic body.

Claim 3

A circuit for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, first detecting means within the magnetic field created by said electromagnet and adapted for response to Barkhausen noise, signal processing means connected to said detecting means for deriving a Barkhausen signal response, second detecting means within the magnetic field for detecting the magnetic flux density of the body in the area of the Barkhausen noise measurement and generating a signal representative thereof, and feedback means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said second detecting means at a predetermined value.

Claim 4

A circuit for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, first detecting means within the magnetic field created by said electromagnet and adapted for response to Barkhausen noise, signal processing means connected to said detecting means for deriving a Barkhausen signal response, second detecting means within the magnetic field for detecting the magnetic flux density of the body in the area of the Barkhausen noise measurement and generating a signal representative thereof, and feedback means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said second detecting means at a predetermined value.

Claim 5

The circuit as described in claim 2, wherein said controllable power generating means comprises a power source for generating a time-varying current, and a variable gain control disposed between said power source and said electromagnet.

Claim 6

The circuit as described in claim 2, wherein said controllable power generating means comprises a variable gain power source for generating a time-varying current.

Claim 7

The circuit as described iN claim 2, wherein said feedback means may include, an amplifier, and a filter for filtering noise detected by said second detecting means.

Claim 8

A circuit for reducing variations in the Barkhausen signal in a body of magnetic material due to the geometry of the magnetic body, the Barkhausen signal being generated within the body responsive to a variable magnetic field, comprising an electromagnet, a power source connected to said electromagnet for passing a time-varying current therethrough, first detecting means disposed within the magnetic field created by the electromagnet and adapted for generating a first signal in response to variations in Barkhausen noise, signal processing means connected to said first detecting means for deriving a Barkhausen signal from said first signal, second detecting means disposed within the magnetic field adjacent said first detecting means for detecting the magnetic flux density of the body in the area of said first detecting means and generating a second signal representative thereof, an amplifier receiving said second signal for amplifying said signal, a filter receiving said amplified second signal and filtering noise detected by said second detecting means, and an operational amplifier connected between said power source and said electromagnet, the power source input being applied as one input to a summing junction, said second signal received from said filter being applied as a second input to said summing junction, the net input signal from said summing junction causing said operational amplifier to control the magnitude of said time-varying current applied to said electromagnet for maintaining the rate of change of the magnetic flux of the body adjacent said second detecting means at a predetermined value.

Claim 9

A circuit for reducing variations in the Barkhausen signal in a body of magnetic material due to the geometry of the magnetic body, the Barkhausen signal being generated within the body responsive to a variable magnetic field, comprising an electromagnet, a power source connected to said electromagnet for passing a time-varying current therethrough, first detecting means disposed within the magnetic field created by the electromagnet and adapted for generating a first signal in response to variations in Barkhausen noise, signal processing means connected to said first detecting means for deriving a Barkhausen signal from said first signal, second detecting means disposed within the magnetic field adjacent said first detecting means for detecting the magnetic flux density of the body in the area of said first detecting means and generating a second signal representative thereof, an amplifier receiving said second signal for amplifying said signal, a filter receiving said amplified second signal and filtering noise detected by said second detecting means, and an operational amplifier connected between said power source and said electromagnet, the power source input being applied as one input to a summing junction, said second signal received from said filter being applied as a second input to said summing junction, the net input signal from said summing junction causing said operational amplifier to control the magnitude of said time-varying current applied to said electromagnet for maintaining the rate of change of the magnetic flux of the body adjacent said second detecting means at a predetermined value.

Claim 12

A circuit for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, detecting means within the magnetic field created by said electromagnet for responding to Barkhausen noise and for detecting the magnetic flux density of the body and generating signals representative thereof, signal processing means connected to said detecting means for deriving a Barkhausen signal response, and feedback means connected to said detecting means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said detecting means at a predetermined value.

Claim 13

A circuit for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, detecting means within the magnetic field created by said electromagnet for responding to Barkhausen noise and for detecting the magnetic flux density of the body and generating signals representative thereof, signal processing means connected to said detecting means for deriving a Barkhausen signal response, and feedback means connected to said detecting means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said detecting means at a predetermined value.

Claim 14

The circuit as described in claim 8, wherein said controllable power generating means comprises a power source for generating a time-varying current, and a variable gain control diSposed between said power source and said electromagnet.

Claim 15

The circuit as described in claim 8, wherein said controllable power generating means comprises a variable gain power source for generating a time-varying current.

Claim 16

The circuit as described in claim 8, wherein said feedback means may include, an amplifier, and a filter for filtering noise detected by said detecting means.

Claim 17

Apparatus for reducing variations in the Barkhausen signal in a body of magnetic material due to the geometry of the magnetic body, the Barkhausen signal being generated within the body responsive to a variable magnetic field, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, a plurality of first detecting means within the magnetic field created by said electromagnet and adapted for response to Barkhausen noise, signal processing means connected to said detecting means for deriving a Barkhausen signal response, a plurality of second detecting means within the magnetic field for detecting the magnetic flux density of the body in the area of the Barkhausen noise measurement and generating a signal representative thereof, and feedback means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said plurality of second detecting means at a predetermined value.

Claim 18

Apparatus for reducing variations in the Barkhausen signal in a body of magnetic material due to the geometry of the magnetic body, the Barkhausen signal being generated within the body responsive to a variable magnetic field, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, a plurality of first detecting means within the magnetic field created by said electromagnet and adapted for response to Barkhausen noise, signal processing means connected to said detecting means for deriving a Barkhausen signal response, a plurality of second detecting means within the magnetic field for detecting the magnetic flux density of the body in the area of the Barkhausen noise measurement and generating a signal representative thereof, and feedback means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said plurality of second detecting means at a predetermined value.

Claim 19

Apparatus for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, a plurality of detecting means within the magnetic field created by said electromagnet for responding to Barkhausen noise and for detecting the magnetic flux density of the body and generating signals representative thereof, signal processing means connected to said plurality of detecting means for deriving a Barkhausen signal response, and feedback means connected to said plurality of detecting means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said plurality of detecting means at a predetermined value.

Claim 20

Apparatus for reducing variations in the Barkhausen signal, generated within a body of magnetic material responsive to a variable magnetic field, due to the geometry of the magnetic body, comprising an electromagnet, controllable power generating means connected to the electromagnet for passing a time-varying current therethrough, a plurality of detecting means within the magnetic field created by said electromagnet for responding to Barkhausen noise and for detecting the magnetic flux density of the body and generating signals representative thereof, signal processing means connected to said plurality of detecting means for deriving a Barkhausen signal response, and feedback means connected to said plurality of detecting means for applying said magnetic flux density signal to said controllable power generating means for controlling the magnitude of the time-varying current applied to said electromagnet and maintaining the rate of change of the magnetic flux of the body adjacent said plurality of detecting means at a predetermined value.