The Magnetostatic Simulation and Determination of Magnetic Components for an External Ventricular Drainage Device

The switch-type Hall sensor is a magnetic sensor based on the Hall effect, which can accurately detect the separation of the two ends of the permanent magnets in a new external ventricular drainage (EVD) device by detecting the change of the magnetic field. The structure of a permanent magnet assembly includes two permanent magnets and a Hall sensor. A finite element model is established to visualize the distribution of the magnetic field, and the simulation is carried out based on Ansys Maxwell 3D. The simulation shows that the magnetic flux density at their junction plane between two permanent magnets reaches the local minimum and that on the edge of each permanent magnet pole reaches the maximum in the pull-in state, and the magnetic induction lines are regular closed curves. In the pull-out state with air gap of 1mm, the magnetic flux density reaches the lowest at the central plane, and the magnetic induction lines intersect. According to the results of simulation analysis, the best detection location of the magnetic flux density is about 2mm away from the permanent magnet lateral surface and -2mm to 2mm away from the junction plane, which is the best range of placement location for the Hall sensor.