Magnet structure

A proximity sensor comprising:

• a housing;
• a magnetic field sensor disposed within said housing;
• and
• a magnet structure disposed within said housing in proximity to said magnetic field sensor, comprising:
• a magnetically permeable concentrator;
• and
• a magnetic element securely affixed to said concentrator by an interference fit between said concentrator and said magnetic element.

A magnetic-field sensor for detecting passing ferromagnetic articles comprising:

• (a) a magnetic-field sensor element for generating an output voltage that is proportional to the ambient magnetic field;
• and
• (b) a magnet structure comprising:
• (i) a magnetically permeable concentrator;
• and
• (ii) a magnetic element integral with said concentrator and positioned adjacent to said concentrator so that an end of each of said concentrator and said magnetic element define a front face of said magnet structure, said concentrator presenting a magnetic field of one polarity at said front face and said magnetic element presenting a magnetic field of the opposite polarity at said front face, said sensor element being positioned adjacent to said front face, wherein an interference fit between said concentrator and said magnetic element prevents said concentrator from being separated from said magnetic element;
• wherein the absolute value of magnetic flux sensed by said sensor element is low when there is no passing ferromagnetic article in the vicinity of said sensor element, high when a ferromagnetic article is proximate said sensor element and low when the valley between two passing ferromagnetic articles is proximate said sensor element substantially independent of the air gap dimension between said sensor element and said passing article.

A proximity sensor comprising:

• a housing;
• a magnetic field sensor disposed within said housing;
• and
• a magnet structure disposed within said housing in proximity to said magnetic field sensor, comprising:
• a ring magnet having an outer diameter and an inner diameter defining a central aperture;
• and
• a magnetically permeable concentrator disposed within said central aperture and having a diameter substantially equal to said inner diameter of said ring magnet.

A magnet structure comprising:

• a magnetically permeable concentrator;
• a magnetic element integral with said concentrator;
• and
• an interface layer disposed between said concentrator and said magnetic element and comprising a chemically bonded portion of said concentrator and said magnetic element.