A novel resonance based magnetic field sensor using a magneto-rheological fluid

A new technique to measure the magnetic flux density based on the resonance principle using magneto-rheological (MR) fluid is proposed in this paper. The magnetic field sensor is designed using MR fluid placed between two piezo laminated circular disc resonators. The resonant frequency of the disc is changed by the magnetic field dependent viscosity of the MR fluid. The key enabling concept in this work is stiffening the circular metal disc using the rheological effect of MR fluid i.e., resonant frequency varies with respect to magnetic field strength. The change in resonant frequency is measured using simple closed loop electronics connected between the two piezo crystals. The analytical model of the vibrating circular discs with MR fluid placed at the center is derived and the results are validated with experimentation. The proposed magnetic flux density measurement concept is novel and it is found to have good sensitivity and also the input output characteristic is piecewise linear.