管内空気柱の音響周波数変化を利用した変位の精密測定 : スピーカによる共鳴法における理論解析

概要

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A new measuring method of displacement by means of variations of sound frequency and length of an air column in a closed resonant pipe has been investigated. This displacement sensor is oscillated by the feedback loop which is composed of a speaker, microphone and phase-locked loop instead of an air jet for the feedback excitation mechanism on the edge instrument. The sound pressure takes the largest value at the resonant frequency. The displacement of the plunger corresponds to the length of the air column. Thus the displacement of the plunger has good correspondence to the resonant frequency of the air column. However the oscillating frequency shifts from the original resonant frequency at the end of the range due to the use of the filter and simple circuit. Thus, the original resonant point is measured by transfer function from the FFT analyzer. An electrical analogy is adopted for theoretical analysis of the acoustic system. The results of the calculations and experiments coincide significantly.
一般社団法人日本機械学会の論文
1991-03-25