Magnetic marker or tag

US6329916A · kind A · utility

Assignee

• Flying Null Limited · GB

Inventor

• Andrew Dames · Cambridge, GB

Key dates

• Filing date: Oct 10, 2000
• Grant date: Dec 11, 2001
• Expiry date: Oct 10, 2020

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/12465
• WIPO field: Control
• WIPO sector: Instruments

Abstract

Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterised by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag compromising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic null as herein defined. Applications of such techniques are described, inter alia, in relation to (a) identifying articled to which tags are attached; (b) accurate determination of position, as in the location of surgical probes; (c) totalisation of purchases, where each item carries a tag coded with data representing its n…