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Wiegand effect

Wiegand effectIn 1975 an American researcher John Richard Wiegand was studying the influence of electromagnetic fields on various types of conductors when he discovered a bright physical effect.He discovered that if a ferromagnetic wire of a special chemical composition and physical structure enters a magnetic field then a spontaneous change of its polarization happens as soon as field density exceeds a definite threshold.This is a threshold of ignition. And if a magnetic field has one direction -- this produces a big positive inductive current step. If it has the opposite direction -- a big negative current step.Wire change of state can be registered by means of a winding around the wire or near it.The Wiegand effect can be used in many spheres. For example, the Wiegand sensors are used in measuring and control systems.The simplest Wiegand sensor consists of a special ferromagnetic wire and winding. The Wiegand wire presented a ferromagnetic body consisting of a soft magnetic core and hard magnetic external cover of the core. Such sensor responses to magnetic fields and produces signals within the range of several volts on condition that the controlling magnetic field density exceeds the density of ignition field. It doesn't require any power supply, its output signal is almost independent from field alteration frequency, and it can be used in a wide range of operating temperatures.