A resonant magnetic sensor

Abstract

The invention provides a resonant magnetic sensor which includes a three-beam structured resonant tuning fork, a piezoelectric drive unit, a piezoelectric detection unit and a phase-locked oscillator. The three-beam structured resonant turning fork is made from a magnetostrictive material and has three oscillation beams each having two ends fixed. The piezoelectric drive unit and the piezoelectric detection unit are composite at the two ends of a middle beam of the three-beam structured resonant turning fork. The piezoelectric drive unit and the piezoelectric detection unit are in respective connection to an input end and an output end of the phase-locked oscillator through electrodes thereof. The phase-locked oscillator is intended for exciting and keeping the three-beam structured resonant turning fork to oscillate in an optimized oscillation mode, and outputting an electric signal which represents the resonant frequency of the three-beam structured resonant turning fork. Since the elasticity modulus of the magnetostrictive material varies along with the static magnetic field, the resonance frequency of the three-beam structured resonant turning fork also changes. Therefore, according to the invention, the resonant magnetic sensor can be used for high-sensitivity detection of static and quasi-static magnetic fields, and has small volume and low cost.

Description

technical field [0001] The invention relates to a resonant magnetic sensor, in particular to a coilless magnetic sensor which uses magnetostrictive materials to form a three-beam tuning fork resonator. Background technique [0002] The traditional types of magnetic sensors mainly include superconducting quantum interference magnetometer (SQUID), Hall sensor, fluxgate magnetic sensor, magnetic sensitive diode magnetic sensor, magnetic sensitive triode magnetic sensor, nuclear magnetic resonance magnetic sensor, optical pump magnetic sensor , giant magneto-impedance sensor, electromagnetic induction magnetic sensor, etc. SQUID is the highest-precision low-frequency magnetic sensor, but it needs to work at low temperature, and it is bulky and expensive; the structures of fluxgate magnetic sensors, nuclear magnetic resonance magnetic sensors and optical pump magnetic sensors are complex, bulky, expensive, and expensive. High consumption; giant magneto-impedance sensors have hig...

AI Technical Summary

Problems solved by technology

This method does not need to use coils, and the circuit construction is simple, but its sensor resonant unit adopts a cantilever beam structure, and the combination of magnetostriction and piezoelectric lamination reduces the detectable sensitivity

The reasons for the decrease in detectable sensitivity are as follows: Under the condition of ideal coupling between layers, the average elastic modulus of the laminated composite structure is: E=n m E. m +(1-n m )E p , where n m is the volume ratio of the composite structure occupied by the magnetostrictive layer, E m and E p are the elastic modulus of the magnetostrictive laminated piezoelectric layer, thus the average elastic modulus change of the laminated structure under the action of a magnetic field is ΔE=n m ΔE m , so the sensitivity of the frequency response is reduced; on the other hand, due to the vibration coupling loss at the fixed end of the cantilever beam structure, the quality factor (Q value) of the cantilever beam resonator is not high enough, which limits the high precision of the magnetic field frequency change detection

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