Apparatus for detecting ferromagnetic objects and screeing people and equipment

Abstract

An apparatus for detecting a ferromagnetic object located on or in a person being screened includes a first magnetic sensor which measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal, a primary power supply provides power to the magnetic sensor, a signal processing circuit is in communication with the magnetic sensors identifies temporal variations in the measurement signal and from the identified temporal variations provides an output signal indicative of the presence of a ferromagnetic object within the volume of space, and a warning device operable by the output from the signal processing circuit provides in the vicinity of the apparatus an audible and a visible warning in response to the output signal from the signal processing circuit. The apparatus may include a user operable input means that disables the warning device without powering down the magnetic sensors.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . Apparatus for detecting a ferromagnetic object located on or in a person being screened, the apparatus comprising:
 At least a first magnetic sensor which in use measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal,   a primary power supply which provides power to the magnetic sensor,   a signal processing circuit arranged in communication with the magnetic sensors configured to identify temporal variations in the measurement signal and from the identified temporal variations provide an output signal indicative of the presence of a ferromagnetic object within the volume of space,   and   a warning device operable by the output from the signal processing circuit to provide within the vicinity the apparatus at least one of an audible and a visible warning in response to the output signal from the signal processing circuit,   and characterised in that the apparatus include a user operable input means which enables the warning device to be disabled by a user without powering down the magnetic sensors.   
     
     
         2 . Apparatus according to  claim 1  in which the signal processing circuit includes one or more filters and in which the output signal from the first sensor is passed through at least one of the filters. 
     
     
         3 . Apparatus according to  claim 2  in which the user operable input means enables the warning device to be disabled without powering down the filters. 
     
     
         4 . Apparatus according to any preceding claim in which the user operable input means alters the value of a relatively low current electrical signal, the apparatus disabling or enabling the warning device according to the value of that signal. 
     
     
         5 . Apparatus according to  claim 4  in which the signal is carried from the user operable input device along twisted pair cables. 
     
     
         6 . Apparatus according to  claim 4  or  claim 5  which includes a second power supply which provides at an output power for the warning device, the output of the second power supply being switchable between a level at which the power to the warning device is enabled and a level at which power to the warning device is disabled, the condition of the output being dependent on the value of the signal from the user operable input means. 
     
     
         7 . Apparatus according to any preceding claim in which the output of the power supply is connected to the signal processing means and warning device through a twisted pair cable. 
     
     
         8 . Apparatus according to any preceding claim which comprises a single housing within which the signal processing means, sensors and power supply are located. 
     
     
         9 . Apparatus according to  claim 8  whereby when in a position of use the user operable input means is located on the housing at a height where it can be pressed by a user of average height without having to stoop down. 
     
     
         10 . Apparatus according to  claim 8  or  9  which includes a mat which in use is positioned on the ground in front of the housing and which indicates where a person must stand to be within the volume of space. 
     
     
         11 . Apparatus according to  claim 8 ,  9  or  10  in which the housing comprises a pole, one of the magnetic sensors is located at, or close to the top of the pole and the other one at or close to the bottom of the pole, and the use operable input means is located conveniently at or close to the midpoint of the pole. 
     
     
         12 . Apparatus according to any preceding claim in which the user operable input means comprises a button or a switch. 
     
     
         13 . Apparatus according to any preceding claim which further includes a second magnetic sensor which in use measures an ambient magnetic field or gradient within a second volume of space that at least partially overlaps the first volume of space and produces a corresponding measurement signal
 and in which the signal processing circuit is configured such that the first and second sensors are configured as a gradiometer.   
     
     
         14 . Apparatus according to any preceding claim which includes a third sensor and the first, second and third sensors are configured as a second order gradiometer. 
     
     
         15 . A method of screening a person or object comprising:
 providing an apparatus comprising a first magnetic sensor which in use measures an ambient magnetic field or gradient within a first volume of space and produces a corresponding measurement signal,   a primary power supply which provides power to the magnetic sensors,   a signal processing circuit arranged in communication with the magnetic sensors configured to identify temporal variations in the measurement signal and from the identified temporal variations provide an output signal indicative of the presence of a ferromagnetic object within the volume of space,   and   a warning device operable by the output from the signal processing circuit to provide within the vicinity the apparatus at least one of an audible and a visible warning in response to the output signal from the signal processing circuit,   the method comprising the steps of:   (a) Positioning the person or object to be screened within the volume of space in a first orientation,   (b) Positioning the person or object in the volume of space in a second orientation which is at least 180 degrees out of alignment with the first position, and   (c) Observing any warning from the warning device.   
     
     
         16 . The method of  claim 15  which comprises a step of rotating the person or object through at least 180 degrees from the first orientation to the second orientation 
     
     
         17 . The method of  claim 16  in which the step of rotating the person comprises rotating them when they are positioned in the volume of space. 
     
     
         18 . The method of  claim 17  in which the step of rotating the patient comprises rotating the patient through at least 360 degrees within the volume of space. 
     
     
         19 . The method of  claim 17  or  claim 18  which includes providing a mat and positioning the patient on the mat, and rotating the person remains standing on the mat, the mat being positioned below the volume o space, and preferably wholly within the zone. 
     
     
         20 . The method of any one of  claims 15  to  18  in which the apparatus includes a user operable input which permits the warning device to be disabled without powering down the magnetic sensors and the method comprises an additional step (d) of powering up the display using the user operable input means. 
     
     
         21 . The method of  claim 20  which further comprises upon completion disabling the display without powering down the magnetic sensors or signal processing means using the user operable input means. 
     
     
         22 . The method of any one of  claims 15  to  21  which includes a step of introducing a magnetic object in front of the device after the display is powered up to test the display prior to position patient. 
     
     
         23 . The method of any one of  claims 15  to  22  whereby the patient is carried in a non ferromagnetic portering means past the apparatus first in one direction and then in the opposite direction in both cases close to the apparatus such that both sides of the patient are scanned. 
     
     
         24 . Apparatus for detecting a ferromagnetic object substantially as described herein with reference to and as illustrated in the accompanying drawings. 
     
     
         25 . A method of screening a person or object substantially as described herein with reference to and as illustrated in  FIG. 6  of the accompanying drawings.