Theoretical And Experimental Study On Magnetic Fluid Micro Differential Pressure Sensor

ABSTRACT:Magnetic fluid is steady colloidal suspensions which is composed by ultrafine (10nm) single-domain magnetic particles coated with surfactant and base carrier. It possesses both ferromagnetism of solid and flow property of liquid. The application of this new kind function material to sensors would improve their performance, such as increasing the linearity and sensitivity, decreasing the volume of sensors and so on.In this paper, a new magnetic fluid micro differential pressure sensor based on Hall elements is proposed, including the structure model of the sensor. Equations of anti-pressure of the sensor are given along with sensitivity equations. What’s more, the structure parameters and materials of sensor components are also determined. In addition, numerical analysis of magnetic restoring force and magnetic field intensity based on ANSYS software are proceeded. Then magnetic fluid micro pressure sensor prototypes are provided, and some preliminary input-output experiments are carried out on the experimental apparatus. Conclusions are shown as follows:(1)The moving magnetic core of Hall magnetic fluid micro differential pressure sensor is permanent magnet absorbing magnetic fluid, and the detecting elements is Hall elements, whose volume is only half than traditional U-type inductance magnetic fluid micro differential pressure sensor.(2)The output experimental values of magnetic fluid micro differential pressure sensor are identical with the theoretical values if the length/diameter radio of the permanent magnet is in an appropriate range, and there is also a fine linearity (linear error less than3.89%). Within certain limits, the larger the initial distance xo of the permanent magnet is, the bigger the sensitivity will be.(3) After optimization to magnetic fluid micro differential pressure sensor, the optimum length/diameter radio of the permanent magnet is1.66(l=10mm), and the optimum initial size xo of the permanent magnet is15mm.(4) After optimization to the magnetic fluid micro differential pressure sensor, the sensitivity is Sen=2.20×10-4V/Pa, the linearity is ef=0.58%, the repeatability error is ez=1.51%, the max stability error is es=2.62%.(5) With in certain limits, the influence of magnetic fluid with different saturation magnetizations and different viscosities to magnetic fluid micro differential pressure sensor is small.