Advanced Magnetoresistance Sensing of Rotation Rate for Biomedical Applications

We propose the use of a magnetoresistive sensor with a non-contacting transduction mechanism to transform the rotor rotation rate into an electrical signal. The rotor is fabricated from polysilicon and coated with a soft magnetic material, such Permalloy, with an in-plane uniaxial magnetization. As the rotor turns, the field from this microscopic magnet modulates the resistance of a bar of a low coercitivity material such as Permalloy placed nearby, close to the rotor flanges. The change in resistivity provides an electrical signal with frequency proportional to the rotation rate, and hence the fluid velocity