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Unformatted text preview: Resistor strips (e.g. Wi- or InSb, Wi=Wismut, In=Indium, Sb=Antimon) change their electrical resistance in magnetic fields. This effect, i.e. magnetoresistive, can be used for various sensor types. Hall proximity sensors If a semiconductor (e.g. InSb) is exposed to a magnetic field, a voltage is created perpendicular to the direction of the current, i.e. the so-called Hall voltage. Certain physical dimensions apply in this particular case, i.e. the thickness of the plate must be small in comparison with the dimensions of length and width. Voltages of up to 1.5 V can be created. The underlying physical effect is described as the Hall effect after the American physicist, E. Hall. 42 © Festo Didactic GmbH & Co. KG • FP 1110 3. Magnetic proximity sensors Wiegand proximity sensors The Wiegand sensors consist of a wire which is made from a ferromagnetic alloy of vanadium, cobalt and iron. The direction of magnetisation of this wire changes spontaneously when an approaching magnetic field exceeds a certain value. If a coil is wound around this Wiegand wire, a voltage pulse of up to 3 V is induced. In principle, Wiegand sensors do not require any external voltage supply. 3.2.2 Technic...
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This note was uploaded on 11/01/2012 for the course CHEMICAL 102 taught by Professor Jamesrodriguez during the Spring '12 term at Universidad Politécnica de Cartagena.

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