| 摘要 |
PROBLEM TO BE SOLVED: To make the displacement of a moving object detectable with resolution from micrometer to nanometer by using a simple structure. SOLUTION: An excitation coil 23 and a detection coil 25 are disposed side by side and a conical magnetic-body probe 27 having a cross-sectional area longitudinally changed is disposed in a form inserted into an air core part of the excitation coil 23. The output terminals from the detection coil 25 are connected to an amplifier 33, and a phase shift circuit 35 is formed between the amplifier 33 and the input terminals of the excitation coil 23. When the magnetic-body probe 27 moves in the air-core part of the excitation coil 23, the inductance of the excitation coil 23 is varied, a phase difference is generated between the input signal of the excitation coil 23 and the output signal from the detection coil 25, and the phase shift circuit 35 changes frequency so as to zero the phase difference. The displacement is detected from the frequency deviation at that time.
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