Design of resonance based DC current sensor using BAW quartz resonators

A novel approach is attempted to measure DC current in the range of 0-0.7 A in this paper. The proposed current sensing system is designed using an AT-cut BAW quartz resonator sandwiched at the center of the rectangular beam. The SMA wire bonded over the rectangular beam changes its shape with the change in input current. The quartz crystal resonator is maintained at first mode resonance frequency using a closed loop resonator electronics. The electric current change in the SMA wire contracts its length which bends the beam and produces an axial force on the quartz resonator which changes the resonance frequency of the BAW crystal placed in between the beam. The shift in quartz crystal resonant frequency is related to the input electrical current in the SMA wire. The analytical model of the entire current sensing system is derived, and the proposed concept is verified experimentally. It is observed that the experimentation results are highly linear, and it has the sensitivity of 350 Hz/A DC current.