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Publication Number
US-11378712-B2
Publication Date
2022-07-05
Expiration Date
Abstract
An apparatus for detecting a moving ferromagnetic target object in a protected area comprises a first magnetic sensor adapted to measure a magnetic field within a first localised volume of space defined by a first zone of sensitivity of the first magnetic sensor and to produce a corresponding first measurement signal, and a second magnetic sensor adapted to measure a magnetic field within a second localised volume of space defined by a second zone of sensitivity of the second magnetic sensor and to produce a corresponding second measurement signal. The two magnetic sensors are separated spatially by a baseline such that the overlap between the two zones of sensitivity defines both a protected zone and a non-protected zone. A signal processing circuit is arranged in communication with the two magnetic sensors and is configured to process each of the first and second measurements signals to produce a respective first intermediate signal and a second intermediate signal which are each independent of the value of any non-changing background magnetic field that may be present in each zone of sensitivity, the value of the first and second intermediate signals thereby being dependent on the magnetic field associated with a target object moving in each zone of sensitivity. The first and second intermediate signals are proportional to the absolute change in magnetic field generated by the movement of the target object. The signal processing circuit also processes the two intermediate signals to provide an output signal that has a value that is indicative of whether the target object that caused the magnetic field is in the protected zone or in the non-protected zone.
Core Innovation
The invention provides an apparatus for detecting a moving ferromagnetic target object in a protected zone. It includes a first magnetic sensor and a second magnetic sensor that are spatially separated by a baseline, where overlap between their zones of sensitivity defines both a protected zone and a non-protected zone. Each sensor measures a magnetic field within its respective localised volume of space and produces corresponding first and second measurement signals.
A signal processing circuit processes the first and second measurement signals to produce respective first and second intermediate signals. Each intermediate signal is independent of the value of any non-changing background magnetic field present in the zone of sensitivity. The intermediate signals are proportional to the absolute change in magnetic field generated by the movement of the target object.
The signal processing circuit further processes the two intermediate signals to provide an output signal indicative of whether the target object that caused the magnetic field is in the protected zone or the non-protected zone. The signal processing circuit is configured to subtract the second intermediate signal from the first intermediate signal, and to use the resulting processed output to distinguish the two regions.
Claims Coverage
The document includes one independent claim directed to an apparatus, with dependent claims that refine sensing, signal processing, and system-level implementation. The independent claim contains three core inventive features: two spatially separated magnetic sensors with overlapping sensitivity defining protected/non-protected zones, intermediate signal generation independent of non-changing background magnetic field and proportional to absolute magnetic-field change, and region-indicative output based on subtraction of intermediate signals.
Overlapping zones of sensitivity defining protected and non-protected regions
A first magnetic sensor and a second magnetic sensor are separated spatially by a baseline such that the overlap between the two zones of sensitivity defines both a protected zone and a non-protected zone.
Background-independent intermediate signals proportional to absolute magnetic-field change
A signal processing circuit processes each of the first and second measurement signals to produce a respective first intermediate signal and second intermediate signal that are each independent of the value of any non-changing background magnetic field, with the value of the intermediate signals dependent on the magnetic field associated with a target object moving in each zone of sensitivity, and proportional to the absolute change in magnetic field generated by the movement of the target object.
Protected-zone vs non-protected-zone output based on subtraction of intermediate signals
The signal processing circuit processes the two intermediate signals to provide an output signal indicative of whether the target object is in the protected zone or in the non-protected zone, wherein the signal processing circuit subtracts the second intermediate signal from the first intermediate signal.
Overall, claim coverage centers on using two spatially separated magnetic sensors whose overlapping sensitivity zones define protected versus non-protected regions, generating intermediate signals that are independent of non-changing background magnetic field and proportional to absolute magnetic-field change from a moving ferromagnetic target, and determining the zone based on subtraction of the intermediate signals.
Stated Advantages
Documented Applications
Protecting an area using a protected-area system with a warning device that operates in response to alert signals indicating whether a target object is in the protected zone or the non-protected zone.
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