Detection System Of Heavy Metal Ions Based On Magnetoelastic Sensor

Magnetoelastic(ME) sensors made of magnetoelastic material thick-film strips, such as amorphous ferromagnetic alloys, are new sensors. ME sensors have gained a lot of attention because of their advantages, high detection sensitivity, low cost, wireless testing, and so on. They can be used in many fields, for example, environment monitoring, food safety and biological element detection.Firstly, the research status of ME sensors was investigated. Based on the vibration equation of ME sensor, the theoretical resonant frequency equation of the sensor is given. The mass load of the sensor which can affect the resonant frequency is discussed, the theoretical equation is given. Through building the theoretical model of ME sensor in liquid, the liquid viscosity and density that effect on the resonant frequency are discussed. Then, three principles for resonant frequency measurement and the commonly used measurement methods in laboratories are presented.Secondly, the impedance de-tuning method, a resonant frequency measurement system of ME sensor using AD5933 impedance converter chip is designed. The designs of hardware circuit and software program are presented, and then the system is tested to verify its measurement accuracy and reliability. Furthermore, a high frequency measurement system of ME sensor is designed, which can conquer the frequency sweeping limitation of AD5933. And the test results show that the frequency below 450 kHz can be measured.Finally, a new detection method for heavy metal ions in solution using bare Metglas 2826 MB resonator is proposed. Based on replacement reaction mechanism, the concentration of heavy metal ions in solution can be determined by bare Metglas 2826 MB resonator without any chemical or biological sensing membrane on its surface. Using Pb(NO3)2 solution, the experimental results prove the reliability of this method. The test results show that the shift rate of resonant frequency increases with the increase of Pb2+ concentration. The resonator with smaller size has better sensitivity. The resonant frequency shift of the resonator is linearly proportional to Pb2+ concentration, and the sensitivity of the resonator is about 24Hz/mg?ml-1.