Study Of New Giant Magnetoimpedance Effect Sensor Characteristics

In this thesis, I will summarize the base situation of the magnetic sensor, including coil sensor, fluxgate sensor, Hall sensor, magnetoresistance sensor, giant magneto resistance sensor, SQUID sensor, and giant magneto-impedance sensor. I will put the emphasis on the principles of the giant magneto-impedance effect. Applying this effect, I have designed a new type magnetic sensor. Finally, I can draw the following conclusions.1. In a non-linear non-diagonal GMI sensor, the pickup coil parameters, including the length, the diameter of coil tube, the number of turns as well as the diameter of the coil wire, in relation to the sensor sensitivity are investigated. The results showed that the sensitivity is directly proportional to the ac driving frequency, and the number of turn density of the pick-up coil. With smaller wire diameter, smaller coil diameter and smaller coil length, the sensor sensitivity improves. Using Co-based glass-coated amorphous microwires 23 μm in diameter as sensing element, the sensitivity is up to 2.3mV/mGs(28.9mV/Am^-1).2. Using the phase sensitive detection method, the output signal in variation with the external magnetic field was converted to a DC signal. The measuring range of the field is ±400 mGs (±31.83 Am^-1). The linearity coefficient is 0.9999, the sensitivityis 5.46 mV/mGs (68.6mV/Am^-1), the resolution response is up to 10^-8 T. By using a digit circuit, the signal can be converted to the digital signal.3. Using high permeability magnetic materials, I have designed a seven layers shielding cylinder with an inside coil to compensate demagnetization and give an offset magnetic field. The DC magnetic shielding factor η7dc is 180 and ac shielding factor is 20 at 0.1 -100Hz.