Development of Magnetic Fluid Acceleration Sensor Operating in an Ultra-Low Frequency Range

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To transport the human body more comfortably on the vehicle or to handle it more flexibly using medical instruments, an novel magnetic fluid acceleration sensor was investigated for stable operation at a frequency as low as a human body resonant.Two-types of mechanism were given consideration : one was the subtraction of the signal owing to the parallel shift of a floating core, the other is the detection of the signal generatedt by a rotating floating core. Finally, the rotating core type was selected for the manufacturing. Experiments were performed with core driving method, core magnetization direction, core radial clearance, rotational speed and environmental temperature as parameters. Performances in the sensitivity and the bandwidth were evaluated using the Bode chart obtained from vibrating the sensor.Excellent linearity and nearly constant sensitivity were confirmed in the range of 0-1 5 Hz. Useful guiding principles in designing the sensor were achieved, such as, thinner core thickness, axial magnetization direction, lower clearance and higher resonant frequency are desirable.