Micromechanical Magnetic Sensor Based on Cylindrical Ferromagnets

In order to solve the problems of cantilever-based magnetic sensors and develop the simple and low-cost magnetic field sensors, novel sensors based on a cylindrical ferromagnet attached to a silicon diaphragm and piezoresistive membrane are proposed. The interaction between the magnetic field and the ferromagnet generates a deflection of the diaphragm, which changes the piezoresistance and unbalances a Wheatstone bridge. The sensitivity of the sensors is proportional to the permeability, supply voltage, and aspect ratio of the ferromagnet. These low-cost, low-power sensors are easily integrated with electronic circuits.