Patent ID: 7146282

Claim:
A method or device for detecting the magnitude of an alternating magnetic field B_signal at a frequency ω_signal, comprising: (a) providing a conductive loop on a vibratable member, wherein the vibratable member has a mechanical resonant frequency ω_mech; (b) driving an alternating current at a frequency ω_loop through the loop, wherein ω_loop≈ω_signal+ω_mech or ω_loop≈ω_signal−ω_mech, thereby creating an alternating magnetic field B_loop in the loop at the frequency ω_loop which interacts with the alternating magnetic field B_signal to exert alternating mechanical force at frequency ω_mech on the loop and vibratable member; (c) detecting a magnitude of vibration of the vibratable member at the mechanical resonant frequency ω_mech and providing an output signal reflecting the magnitude of the vibration of the vibratable member; whereby the magnitude of the alternating magnetic field B_signal at the frequency ω_signal is reflected in the magnitude of vibration of the vibratable member at frequency ω_mech.