Research On Magnetic Induction Detection Technology Based On Magnetoelectric Sensors

Magnetic induction detection technology has received widespread attention for its ability to detect and analyze passive electromagnetic properties of conductive objects in a non-contact and non-invasive manner,and is widely used in fields such as non-destructive testing and biomedical engineering.By analyzing the phase difference between the induced and excited magnetic fields,it is possible to detect information such as conductivity and geometric parameters of the detecting objects.Currently,most magnetic induction detection techniques use coils for magnetic field detection,and the coils need to operate at high excitation frequencies(MHz),but high excitation frequencies can lead to insufficient detection depth due to the skin effect.But the magnetoelectric(ME)sensor has extremely good performance at kilohertz resonant frequency,not only to reduce the excitation frequency to kilohertz,but also to increase the detection depth while ensuring the detection sensitivity,which can effectively solve the problem of high excitation frequency and insufficient detection depth.Therefore,this thesis conducts research on ME sensor-based magnetic induction detection technology:First,the magnetic induction detection simulation is performed using finite element simulation software.After comparative analysis,the Helmholtz coil,which can make the detection sensitivity more uniformly distributed,was selected as the excitation coil.Then,after the feasibility analysis of the kilohertz excitation frequency,the 20 kHz frequency was chosen to simulate the magnetic induction detection of copper and brine balls in terms of volume and distance,and the results showed that the phase difference increased with the volume and decreased with the distance,and the functional relationship between the phase difference and the volume and distance was obtained by function fitting.In addition,a cranial simulation model was established to simulate the occurrence of bleeding inside the skull,and the results showed that the phase difference increased with the amount of bleeding.The simulation results of magnetic induction detection can provide guidance and basis for the subsequent magnetic induction detection experiments.Secondly,a ME sensor-based magnetic induction detection system was designed and built,including a direct-reading ME sensor composed of a ME composite material and a pre-charge amplifier,an excitation module composed of a signal source,a power amplifier and a Helmholtz coil,an acquisition module composed of an acquisition card and an acquisition program,and a phase discriminator.The Metglas/PZT/Metglas-based direct-reading ME sensor has an equivalent magnetic noise of 218 fT/√Hz at the resonant frequency of 20.576 kHz and a magnetic field detection limit of 250 pT in the time domain,a performance that is at the top international level.Combined with the acquisition module,the phase detection accuracy of the AD8302 discriminator reaches0.002°,a performance that is comparable to existing high-precision phase detection systems.Finally,the experiment is conducted using the built ME sensor-based magnetic induction detection system.The phase stability experimental results show that the phase drift of AD8302 discriminator,power amplifier and direct-reading ME sensor are0.005°,0.008°and 0.167°respectively within 1 h,which confirms the good phase stability of the system.In addition,the volume,axial distance,radial distance and conductivity detection experiments were performed on brass balls and brine,and the experimental results were in good agreement with the simulation results in terms of variation trends.The system has a volume detection limit of 1.77 cm~3,a distance detection limit of 4.5 cm,and a conductivity detection limit of 21 S/m for brine,indicating that the constructed magnetic induction detection system has reliable magnetic induction detection capability and has important application potential in the field of biomedical engineering.In this paper,a ME sensor-based magnetic induction detection system is established under the guidance of the simulation results of magnetic induction detection.Then the detection experiments were conducted using brass balls and brine,and the experimental and simulation results were in good agreement,which verified the reliability of the detection system.The proposed detection system provides a new candidate technology in the field of magnetic induction detection,which has important application prospects in the fields of nondestructive testing and biomedical engineering,and is expected to promote the application of magnetic induction detection technology in industry.