| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a proximity sensor detecting and notifying disconnection of a detection coil. <P>SOLUTION: This proximity sensor includes an LC resonance circuit 1 including a detection coil 10 and a capacitor 11, an output circuit 4 to output a detecting signal indicating whether or not an object to be detected exists, and a disconnection detecting part 5 to detect disconnection of the detection coil 10. The disconnection detecting part 5 has a discriminating circuit 50 to determine the disconnection if an input voltage exceeds a prescribed threshold, a trigger circuit 51 to boost the input voltage only in a positive period in which a voltage (reference voltage) between both terminals of the capacitor 11 is not less than a positive prescribed voltage, and a trigger nullifying circuit 52 to drop the input voltage only in a negative period in which the reference voltage is less than the positive prescribed voltage. The threshold is set at a value exceeded by the input voltage when the positive period is continued for a prescribed period longer than a half cycle of the oscillation cycle of the LC resonance circuit 1, and the output circuit 4 outputs the disconnection signal indicating disconnection if the disconnection is determined by the disconnection determining part 5. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
