Of Digital The Gmi Weak Magnetic Sensor Technology Research

Since the Giant Magneto-impedance (GMI) effect was found, GMI magnetic sensor has shown wide application prospects to measure weak magnetic field with its high sensitivity and rapid response. In this dissertation, the characteristics of GMI materials are investigated with assistance of the theory of the GMI effect. On that basis, a digital GMI micro-magnetic sensor is designed.First, Fe-based amorphous ribbon is chosen to be the sensing material after researching on different kinds of GMI materials. A sensing element is designed with Fe-based amorphous ribbon based on the longitudinal excitation. The parameters of the element are decided by a series of experiment to make sure the impedance of the element can change observably with the variation of external magnetic fields. Then, a multivibrator is constructed using the sensing element as an inductive element. Both a frequency-modulation-type and a PWM-type GMI sensor are designed. The frequency-modulation-type sensor is designed as key task with regard to the design of the multivibrator circuit, the data acquisition circuit and the communication interface. At the same time, the software is designed to realize the function required. At last, the static and dynamic characteristics of the sensor designed are analyzed. A nonlinear correction by software is designed to improve the performance of the sensor.With the experiment results, it is concluded that the sensor designed has good performance with the external magnetic field strength range of±2Oe. More than that, the output of the multivibrator can be acquired by MCU directly without an A/D converter. Compared with conventional magnetic sensors, the digital GMI sensor designed is promising to have smaller size, more rapid response, higher stability and lower cost.