Magnetoelastic Vibration Sensors

In this work, we explore the application of magnetoelasticity towards the realization of vibration transducers. Such sensors have unique and complementary properties when compared against more conventional transduction schemes. The sensors can be constructed to have a native response to jerk, the time derivative of acceleration. Acceleration causes force on an internal mass, the force induces strain on a magnetoelastic material, and the strain produces a magnetic field. The time derivative of magnetic flux through a voice coil results in a measurable voltage, consistent with Faraday’s law. Taken together, the generated voltage is directly proportional to applied jerk. Because of this native jerk response, the transducer’s frequency response has a 6 dB/octave slope compared to accelerometers and a 12 dB/octave slope compared to geophones. A second noteworthy feature is that, like geophones, magnetoelastic sensors have low output impedance and can, therefore, be used without amplification electronics in many applications. This may be ideal for applications requiring large networks of sensors.