US Patent 7915890 High sensitivity magnetic sensor

A sensor device comprising a base substrate and first and second flux concentrator fixedly attached to the base substrate. The first flux concentrator and the second flux concentrator are positioned with their proximal end regions facing and spaced apart, defining a gap therebetween. A magnetic sensor element is positioned in the gap, the sensor element moveable towards and away from the base substrate. The sensor device has a first system to offset stray magnetic fields, a second system to modulate the sensor element to detect KHz frequency, and a third system to dither noise from the first and second flux concentrators.