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If the pole axis is parallel to the switching reeds

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Unformatted text preview: .2.3 Detecting a magnetic field The most simple and usual method of detecting a magnetic field is to use a reed switch. Two soft magnetic metal reeds are brought into contact by means of an external magnetic field and an electrical contact is established. Closing of this contact is however not bounce-free. Fig. 11.2.4 illustrates the switching behaviour of this contact. ON OFF t1 t2 t Fig. 11.2.4: Switching characteristic of bouncing mechanical contacts © Festo Didactic GmbH & Co. KG • FP 1110 169 11. Physical fundamentals Furthermore, it should be noted that this switch has two or three switching zones depending on the direction of the magnetic pole axis. If the pole axis points vertically in the plane of the switching reeds, then two switching zones will always be obtained (Fig. 11.2.5). This is due to the shape of the magnetic flux pattern. When the magnet passes, the field strength which is required to trigger the switch is obtained twice. If the pole axis is parallel to the switching reeds, t...
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