| 摘要 |
<p>An inductive proximity switch is provided which comprises a coil, means for supplying the coil with periodic transmitting current pulses, and means for processing the signals which correspond to voltages induced in said coil after the end of a transmitting current pulse by the decaying current which previously flows in the detected body due to the voltage induced therein by the transmitting current pulse. In order to improve the properties of the proximity switch, the supply means are adapted to supply the coil (11) with transmitting current pulses whose direction alternates periodically, the current flow pattern being such that in the first half of a period (T21) of the current supplied to the coil (11) by the supply means, the transmitting current delivered to said coil (11) by the supply means flows in a first direction and substantially only during a first interval (T1) which is shorter than one half of the period (T21) of the transmitted pulses, said transmitted current subsequently decays during a time interval (T11'), and is negligibly small during the remaining time (T12-T11') of the first half of the period, and in the second half of the period (T21), the transmitting current delivered to the coil (11) by the supply means flows in a direction opposite to the first one and substantially only during a second interval (T13) which is shorter than one half of the period (T21) of the transmitted pulses, said transmitted current subsequently decays during a time interval (T13'), and is negligibly small during the remaining time (T14-T13') of the second half of the period.</p> |
