A marker for use in a system for inspection of articles, method of manufacturing the same.Method and system for detecting the presence of an article in a zone of interrogacao and method of desativacao one marker of inspection of articles

摘要

A magnetic marker is formed from a magnetic material having a hysteresis characteristic which is such that upon subjecting the material to an applied alternating magnetic field, the magnetic flux of the material undergoes a regenerative step change in flux at a threshold value when the field increases to the threshold value from substantially zero and undergoes a gradual change in flux when the field decreases from the threshold value to substantially zero. For increasing values of applied field below the threshold, there is substantially no change in the magnetic flux of the material. The aforesaid hysteresis characteristic of the marker is achieved by causing the material to have domains with a pinned wall configuration. Deactivation of the marker is realized by disabling the pinned walls from returning to their pinned condition via application of a deactivation field of high frequency and/or amplitude.