| 摘要 |
<p>An inductive proximity switch for detecting the presence of an object in a monitored area, comprising a coil (2), a pulse source (4) for supplying said coil (2) with transmitting current pulses (S1, S2, S3) at a period (T) larger than the duration (Ts) of said transmitting current pulses, and a processing circuit (6) for generating an output signal (9) based on received voltages (Ui1, Ui2, Ui3) varying in dependence of a change of position of the object, said received voltages being induced in said coil (2) after the duration (Ts) of a transmitting current pulse by the decaying current which previously flows in the object due to the voltage induced therein by said coil. An output signal that is less sensitive to external perturbing fields can be provided by equipping the proximity switch with a suppression circuit (13, 13a, 13b, 13c) for suppressing a signal duration lower than a predetermined perturbation time (Tc1, Tc2) in said output signal (9) such that the minimum time interval between two variations of said output signal does not go below said perturbation time (Tc1, Tc2).</p> |
