| 摘要 |
<p>A two-wire coil, comprising substantially two coil conductors with one each end thereof commonly connected to and stranded with each other, with one coil conductor used as a coil (L1) for a resonance circuit and the other coil conductor as a coil (L2) for compensating copper resistance, is used for a detection coil (11). A high frequency oscillation type proximity sensor capable of improving the detection sensitivity thereof, comprises an oscillation drive circuit (12) for oscillating the detection coil by feeding the drive current to the commonly connected end of this two-wire coil, a buffer (13) for taking out the oscillation output voltage generated on one end of the two-wire coil, and a phase-shift circuit (15) for canceling the copper resistance component of the two-wire coil by turning the phase of the oscillation output voltage taken out by the buffer by a predetermined angle to be fed back to the coil for compensating copper resistance. The oscillation drive circuit comprises a non-linear amplifier (21), and the soft oscillation characteristic is given to the high frequency oscillation circuit comprising the non-linear amplifier and the two-wire coil by changing the amplitude of the oscillation voltage generated in the two-wire coil in multiple stages.</p> |
