High ferrous shielding ratio for magnetic proximity switch applications

Ferrous shielding is commonly used for magnetic proximity (vane) switches. In such systems a movable ferro-magnetic object is detected when it resides between a static magnet/sensor assembly as the field of the magnet is shielded. A crucial factor with respect to robustness and also the achievable distance is the ratio of the magnetic field for the unshielded and the shielded situation. This is of particular interest when the shielding object is small. In this paper we present a magnetic multipolar configuration for the field generation and demonstrate the increase of the shielding ratio by means of 3D-FEM simulations as well as experimental investigations. The new approach permits the use of various source/sensor combinations, which opens up a wide range of applications.