Design Of Pressure Sensor Based On Giant Magneto Impedance Effect

In this paper,based on the theoretical study of giant magnetoimpedance effect of amorphous alloy materials,the magnetic properties of cobalt based amorphous ribbons are experimentally studied,and a pressure sensor is developed using the amorphous ribbons.The main research content is as follows:By modeling the amorphous belt,and using the Landau-Lifshitz dynamic equation and Maxwell equations of magnetization under the action of stable magnetic field and alternating magnetic field,the expressions of permeability tensor and impedance of the amorphous belt under the action of high-frequency AC signal excitation and external DC magnetic field are solved.And two experiments were designed to lay the foundation for the development of pressure sensors.A pulse annealing circuit was designed to heat treat the amorphous strip,and the annealing effect of the amorphous strip under different annealing parameters was studied.The experiment shows that when the pulse current density is 100A/mm2 and the pulse frequency is 1Hz,the optimal annealing effect is achieved;Maintain the pulse frequency at 1Hz and change the density of the pulse current.When the pulse current density is 127A/mm~2,the output voltage change rate of the amorphous strip is the highest.Finally,the optimal annealing parameters for the amorphous strip used in this experiment are determined.Exploring the relationship between the change rate of output voltage of amorphous ribbons and the excitation signal parameters,the experimental results show that when the amplitude of the signal source excitation signal remains unchanged and the excitation signal frequency is at 1MHz,the output voltage change rate of amorphous ribbons is the highest;Maintain the excitation signal frequency at 1MHz and change the amplitude of the excitation signal.The larger the amplitude,the greater the rate of change of the output voltage of the amorphous ribbon.Using the displacement platform design experiment,the relationship between the displacement of the magnetic needle and the output signal of the amorphous belt is studied.The experimental results and the theory of the equivalent current model of the magnetic field of the cylinder permanent magnet show that the displacement of the magnetic needle in a certain displacement is linearly related to the output signal of the amorphous belt.From this,the basic principle of the pressure sensor based on the giant magnetoimpedance effect is determined.The distance between the magnetic needle and the amorphous belt is changed by pressure,Convert the pressure signal into the output voltage signal of the sensor.The overall design of the sensor includes four parts:a corrugated diaphragm,sensitive components,excitation signal generation circuit,and signal processing circuit.During the testing of sensors,due to limited experimental conditions,ANSYS finite element analysis software was used to perform mechanical analysis on the corrugated membrane,providing corresponding data and curves of pressure and center displacement of the corrugated membrane.The simulated displacement of the membrane center was converted into the displacement of the magnetic needle on the displacement platform.Through the displacement platform,the displacement of the magnetic needle and the output voltage of the sensor were tested,and the pressure value was corresponding to the output voltage of the sensor,And use the least squares method to obtain the fitting curve expression between pressure and sensor output voltage.The final pressure sensor designed for this project has a range of approximately 0-0.55MPa and a sensitivity of approximately 0.545V/MPa.