To improve precision in displacement detection by reducing or eliminating the influence of a change in the characteristics of a resonance circuit in a resonant displacement detecting device.
In a displacement detection system 10, a resonance frequency range allowed by the resonance circuit 21 is preestimated, fluctuation ranges f1-f2 in a drive frequency are determined so that the estimated resonance frequency range is included, the drive frequency is repeatedly changed between first and second frequencies f1 and f2 by a variable oscillator 30. Therefore, when the resonance frequency of the resonance circuit 21 is fr1, a resonance voltage Vgl1 when a gap G is large can be obtained, when the drive frequency changes to fr1. And when the resonance frequency of the resonance circuit 21 is fr2, a resonance voltage Vgl2 with the large gap G can be obtained when the drive frequency changes to fr2.
MORI AKIRA
HAYASHI ITSUKI
NAKABAYASHI MUNEHARU
