Theoretical And Experimental Study On Magnetic Fluid Level Sensor

Magnetic fluid which is characterized by the unique combination of fluidity and the capability of interacting with a magnetic field have been used as a sensitive element of magnetic fluid level sensor which is a novel research field in current. Depending on magnetic fluid is flowing with a small inclination attitude of the measured body, the inclination angles should be transferred into electric signal as output voltage through transition elements by inducing the variation of self-inductance. While the magnetism properties of magnetic fluid impact directly on the application character of magnetic fluid level sensor, the research on the principle of magnetic fluid level sensor is the theoretical laws and the practical foundation for the research of selection and preparation of magnetic fluid, of parameter design, and of the properties of output signal and sensitivity of this level sensor.Based on analysis of magnetism properties of magnetic fluid which is coherent to the application of magnetic fluid level sensor, appropriate magnetic fluid were selected and prepared and the mathematic model for the principle of magnetic fluid level sensor was established. Meanwhile, influencing factors and regularity on the output signal and sensitivity of this level sensor were disclosed. In succession, numerical simulation and experimental research of magnetic fluid level sensor were put up for further analysis of experimental and structural parameters, while the method and laws which the parameter design determined by were proposed.By analysis on the principle of magnetic fluid level sensor, the linearity relationship between output voltage and the level inclination angle was deduced and the expression of sensitivity of this sensor was put forward. After three kinds of kerosene based magnetic fluid with different magnetism properties were prepared, an experimental model was designed for experimental research on this magnetic fluid level sensor. And then, the influence regularity on output voltage and sensitivity of magnetic fluid level sensor caused by magnetism properties of magnetic fluid, by structure parameter of experimental model, and by input voltage and pumping frequency and so on was analyzed. It was known that the measurable level inclination angle of one-dimension magnetic fluid level sensor could reach to the maximum when the half-volume magnetic fluid was filled into the vessel of experimental model. The maximal measuring range of this magnetic fluid level sensor would determined by the ratio between internal diameter and inwall length of the vessel of experimental model, that is to say, it would decided by the tangent of maximal level inclination angle. According to the maximal measurable level inclination angle, the physical dimension of the vessel which contained the magnetic fluid should be settled. In response to sensor sensitivity demand, the structural parameters as well as winding and arranging manner of exciting and inducing coils should be selected. When the structural parameters was defined, the sensitivity of magnetic fluid level sensor was linear to the susceptibility of magnetic fluid, to the effective value of input voltage, and to the pumping frequency of exciting signal, but was independent with the measured inclination angle.In the basement of analysis and research on the principle of magnetic fluid level sensor, the numerical simulation on the working situation of the experimental model was approached by analysis of electromagnetic coupling using ANSYS software. A useful method utilized in the situation without actual test was provided for emulation of working condition and output signals of this sensor. An estimation approach of output signal and sensitivity of this sensor was proposed as well as the experience data was given for parameter design of this magnetic fluid level sensor.