| 摘要 |
PROBLEM TO BE SOLVED: To provide a proximity sensor which easily detects whether a displacing body approaches or not by excluding environmental variation like variation in ambient temperature.SOLUTION: The proximity sensor includes: a first resonance circuit 1 including a detection coil L1 whose electric or magnetic characteristics are varied in accordance with displacement in a direction to be detected of a displacing body M1; a second resonance circuit 2 including a reference coil L2 more hardly affected by an influence of displacement of the displacing body M1 than the detection coil L1; a first oscillation circuit 3 connected to the first resonance circuit 1; a second oscillation circuit 3' connected to the second resonance circuit 2; a detection circuit 4 which detects whether the displacing body M1 approaches or not on the basis of an oscillation voltage V1 of the first resonance circuit 1; and a feedback control circuit 5 which controls conductance G0' of the second oscillation circuit 3' so as to fix an amplitude of an oscillation voltage V2 of the second resonance circuit 2. The feedback control circuit 5 controls conductance G0 of the first oscillation circuit 3 also in linkage. |
