Optimization Design Of Detecting System For Magnetoelastic Resonance Sensors

Magnetoelastic(ME) sensor is a new resonant sensor based the amorphous alloys. The excitation and transmission of its signals are carried out by magnetic field. When placed to an external alternating magnetic field, the ME sensor is excited and mechanically vibrate along its length. When the frequency of the AC field is equal to the mechanical resonance frequency of the sensor, the sensor vibrates at its characteristic resonance frequency, which shifts in response to mass loading, and the vibration amplitude is maximal. The vibration of the sensor in turn generates a time varying magnetic flux, which can be measured with a pick-up coil. According to above, the resonance frequency is detected. The ME sensor is completely passive, and there is no physical connection between the sensor and the detection circuit. The wireless, passive features make ME sensor great application prospects in no-destructive detection, in situ and in vivo analysis.In allusion to the insufficient of the present detection system for ME sensor,such as large volume, complex operation and so on. Our research group implemented an integrated detection system for the resonance characteristic of ME sensor based on the impedance method. In order to optimize this system, the working magnet field of ME sensor has been simulated and analyzed by Ansoft Maxwell 3D. Based on this, the new solutions to the magnetic field for ME sensors was advanced, and the new spiral coil was designed to provide the excitation magnet field. All of the above is theory reference for the optimization.Meanwhile, the parameters of detection coils and excitation coils were optimized, and the test of sensors’ optimal electromagnetic excitation parameters on the impedance analyzer was carried out with the new coils. According to the requirement of the testing parameter, a detecting system for ME resonance sensors based on the idea of function modularization. The system hardware has been divided into several functional modules to give priority to the function correlation analysis. The modules are connected to the base-circuit-board by standardized interface in accordance with the different situation, so the feasible methods, including impedance de-tuning method and frequency-domain measurement, can be integrated in the same system perfectly. According to the principle of frequency sweeping and impedance method, a variety of function modules have been designed, including MCU module, communication module, coil module, DC bias module(DC current and DC voltage), AC excitation module(AC current and AC voltage), response signal(Amplitude and Frequency) detection module and power supply module.The detecting systems for ME resonance sensors based on frequency sweeping and impedance method have been set up by taking advantage of the function module. Besides, the functional verification and the performance test also were carried out on the both systems, including repeatability of the systems, test of different length sensor and test in different medium. The results indicate that the systems can detect the resonance characteristic accurately, and the systems have better flexibility and operability under the premise that guarantees the good stability and repeatability. The systems can be better applied to detect objects through the combination and matching of modules. In addition, the double coil difference detection system has been set up with the spiral coil on the basis of frequency sweeping. The results indicate that the system not only removes the limitation of detect objects’ volume, also can eliminate the interference of excitation signal and some background noise.Finally, the preliminary research on the ME p H sensors has been carried out on the impedance detection system. The sensors coated with p H sensitive polymer have been prepared successfully, and the sensitivity and linear range of the sensor were tested. The influence of different preparation methods and distractions also was analyzed.