High Q-value resonance magnetic sensor employing frequency conversion output

A magnetic sensor and frequency conversion technology, which is applied in the direction of magnetic field measurement and magnetic field size/direction by using electromagnetic devices, can solve the problem of high-precision detection of limited magnetic field frequency changes, high mechanical damage of magnetostrictive materials, and low frequency response sensitivity and other issues to achieve the effect of low cost, small size and fast response

Inactive Publication Date: 2017-06-20
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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 high mechanical damage of the magnetostrictive material itself, the quality factor (Q value) of the cantilever beam resonator is limited, which limits the frequency change of the magnetic field. High-precision detection

Method used

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  • High Q-value resonance magnetic sensor employing frequency conversion output
  • High Q-value resonance magnetic sensor employing frequency conversion output
  • High Q-value resonance magnetic sensor employing frequency conversion output

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Embodiment 1

[0023] combine figure 1 , in this embodiment, the high-Q resonator in the magnetic sensitive unit 5 is a three-beam resonator, and the magnetic sensitive unit 5 shown includes a three-beam resonant structure 1-1, a piezoelectric drive unit 2-1, a piezoelectric detection Unit 2-2, resonator holder 3 and magnetostrictive unit 4.

[0024] The three-beam resonant structure 1-1 shown is essentially a tuning fork, which is an integrated sheet structure and can be made of low-loss elastic materials such as Si and elastic steel. The three-beam resonant structure 1 has three vibrating beams fixed at both ends, such as figure 1In the middle beam 1-10 and the two side beams 1-20, the width of the middle beam 1-10 is approximately twice the width of the side beams 1-20. In the optimized vibration mode, the vibration direction of the middle beam 1-10 is opposite to that of the two side beams 1-20, so that the bending moments and shear forces of the middle beam 1-10 and the two side beams...

Embodiment 2

[0027] combine figure 2 , in this embodiment, the high-Q resonator in the magnetic sensitive unit 5 is a single beam resonator, and the magnetic sensitive unit 5 shown includes a single beam resonant structure 1-2, a piezoelectric drive unit 2-1, a piezoelectric detection unit Unit 2-2 and magnetostrictive unit 4. The single-beam resonant structure 1-2 has only one vibrating beam, the piezoelectric drive unit 2-1 and the piezoelectric detection unit 2-2 are compounded at both ends of the beam, and the upper and lower surfaces have electrodes, and the lower electrode is the electrode in contact with the beam . In this embodiment, the magnetostrictive unit 4 is a hollow structure, and the two ends of the vibration beam of the single-beam resonant structure 1-2 are directly compounded on the magnetostrictive unit 4 of the hollow structure, and the position of the vibration beam corresponds to the hollow structure, forming a vibration The beam is fixed at both ends and suspende...

Embodiment 3

[0029] combine image 3 , in this embodiment, the high-Q resonator in the magnetic sensitive unit 5 is a quartz resonator, and the magnetic sensitive unit 5 shown includes a quartz resonant structure 1-3 and a magnetostrictive unit 4 . The quartz resonant structure 1-3 is a rectangular quartz crystal sheet, and electrodes 6 are symmetrically plated in the middle of its upper and lower surfaces (the electrodes on the lower surface are not shown). When voltage excitation is applied to the electrodes 6 on the upper and lower surfaces, the quartz crystal resonates, and due to the energy limit theory, the vibration of the quartz crystal is limited within the range of the electrodes and has a high Q value. For example, if the quartz crystal adopts an AT cut shape, the electrodes 6 on the upper and lower surfaces will vibrate in thickness shear under voltage excitation, and the resonant frequency in this vibration mode is sensitive to the longitudinal magnetostrictive stress. In thi...

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Abstract

The invention discloses a high Q-value resonance magnetic sensor employing frequency conversion output. The high Q-value resonance magnetic sensor includes a magnetic sensing unit, an oscillating circuit and a frequency detecting circuit. The magnetic sensing unit includes a magnetostriction unit and a high Q-value resonator integrated to the magnetostriction unit. The magnetostriction unit loads magnetostriction stress to the high Q-value resonator due to the effect of a magnetic field. The oscillating circuit excites the high Q-value resonator to oscillate and outputs electric signals carrying resonance frequency of the high Q-value resonator. The frequency detecting circuit detects the resonance frequency. The high Q-value resonance magnetic sensor provided by the invention can be used for high-flexibility detection of static, quasi-static and low frequency magnetic fields and is small in size and low in cost.

Description

technical field [0001] The invention relates to a resonant magnetic sensor, in particular to a resonant magnetic sensor using a frequency conversion method. Background technique [0002] The development of magnetostrictive materials with large magnetostriction coefficients has brought new opportunities for the development of magnetic sensors. Combining magnetostrictive materials with piezoelectric materials will produce magnetoelectric effects due to the "product effect", which can be directly used for dynamic magnetic field detection with a sensitivity of up to 10 -11 T(Shuxiang Dong,Jie-Fang Li,and D.Viehland,Ultrahigh magneticfield sensitivity in laminates of TERFENOL-D and Pb(Mg 1 / 3 Nb 2 / 3 o 3 –bUltO 3 crystals, Appl. Phys. Lett., vol.83, no.11, 2003). However, due to the capacitive characteristics of the piezoelectric material layer, the piezoelectric layer and the input impedance of the measurement circuit form a high-pass filter during measurement, and the magnet...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R33/06
CPCG01R33/06
Inventor 卞雷祥文玉梅李平
Owner NANJING UNIV OF SCI & TECH
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