Experimental error analysis of measuring the magnetic self-levitation force experienced by a permanent magnet suspended in magnetic fluid with a nonmagnetic rod

The self-levitation of permanent magnet in magnetic fluid has been widely used in sensors, actuators, dampers, bearings, and lubrication in micromechanical systems. In this paper, the magnetic self-levitation force (MSLF) experienced by a permanent immersed in magnetic fluid is studied, and the formula for calculating the MSLF is derived. To measure MSLF experimentally, a nonmagnetic rod is used to connect the magnet and dynamometer. The experimental error caused by the nonmagnetic rod is studied theoretically, and nonmagnetic Cu rods with different radii are used in the experiments to verify the theoretical analysis. With nonmagnetic Cu rod sticking on the top surface of the magnet, the experimental error caused by the nonmagnetic rod is negligible when the magnet moves down from center of the container. However, the experimental error can't be ignored when the magnet moves up. In addition, the simulation results are in good agreement with the experimental results when the magnet moves down.