Apparatus for detecting ferromagnetic objects and screening people and equipment

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.

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, wherein the apparatus includes a user operable input device which enables the warning device to be disabled by a user without powering down the magnetic sensors.