Ferrous target identification system with magnetic field polarity and gradient indication
First Claim
1. A target identification system for a gradiometer for detecting a desired ferrous object concealed beneath a surface, said system comprising:
- (a) a first sensor for detecting a magnetic field at a first point above the surface;
(b) a second sensor for detecting said magnetic field at a second point above the surface, said second point located above said first point;
(c) means for providing drive signals for the sensors, connected the first and second sensors, to generate sensor output signals proportional to the magnetic fields sensed by the sensors;
(d) circuit means connected to the first and second sensors and including means for generating a difference signal at an output thereof, said difference signal being the difference between the output signals of the sensors and being proportional to the detected gradient of the magnetic field between said first point and said second point, the circuit means also generating a polarity signal indicative of the magnetic field polarity at the first sensor; and
(e) interface means for producing an indication signal when both said polarity signal has a selected value, indicative that said magnetic field has a selected polarity and when said difference signal has a magnitude that exceeds a set value, indicative that the magnitude of the detected magnetic field gradient exceeds a set value, the interface means being connected to the circuit means.
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Accused Products
Abstract
A target identification system for detecting a desired ferrous object concealed beneath a surface is provided for a gradiometer. The system has first and second sensors for detecting a magnetic field at a first and second points above the surface. A device for providing drive signals for the sensors is connected to the sensors, to generate sensor output signals proportional to the magnetic fields sensed by the sensors. The outputs of the sensors are connected to means for generating a difference signal at an output thereof, the difference signal being the difference between the output signals of the sensors and being proportional to the detected gradient of the magnetic field between the first and second points. An interface receives the difference signal for producing an indication signal when said magnetic field has a selected polarity and when the magnitude of the detected magnetic field gradient exceeds a set value. For example, the interface can comprise a pair of LEDs, for the two different polarities, which are only activated if a threshold is exceeded. This enables a user to distinguish unwanted objects which typically will show an opposite polarity from target objects.
18 Citations
22 Claims
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1. A target identification system for a gradiometer for detecting a desired ferrous object concealed beneath a surface, said system comprising:
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(a) a first sensor for detecting a magnetic field at a first point above the surface; (b) a second sensor for detecting said magnetic field at a second point above the surface, said second point located above said first point; (c) means for providing drive signals for the sensors, connected the first and second sensors, to generate sensor output signals proportional to the magnetic fields sensed by the sensors; (d) circuit means connected to the first and second sensors and including means for generating a difference signal at an output thereof, said difference signal being the difference between the output signals of the sensors and being proportional to the detected gradient of the magnetic field between said first point and said second point, the circuit means also generating a polarity signal indicative of the magnetic field polarity at the first sensor; and (e) interface means for producing an indication signal when both said polarity signal has a selected value, indicative that said magnetic field has a selected polarity and when said difference signal has a magnitude that exceeds a set value, indicative that the magnitude of the detected magnetic field gradient exceeds a set value, the interface means being connected to the circuit means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification