A new measuring method of displacement by means of variations of sound frequency and the length of air column in a small pipe. A resonant method by using speaker and electric feedback loop.

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  • 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　スピーカと電気的フィードバックループによる共鳴法
  • カンナイ クウキチュウ ノ オンキョウ シュウハスウ ヘンカ オ リヨウシタ

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A new measuring method of displacement by means of variations of sound frequency and length of air column in a closed resonant pipe has been investigated. In this paper, a speaker is used as a sound generating source in stead of air jet for the feedback excitation mechanism on the edge instrument. This paper deals with a new kind of displacement sensor using a electric feedback circuit. A sweep signal is radiated from the speaker through the small hole at one end of the closed resonant pipe toward inside of the air column. The sound pressure takes the largest value at the resonant frequency. The displacement of the plunger which is inserted from other end of the pipe, corresponds to the length of the air column. So, the displacement of the plunger makes good correspondence to the resonant frequency of the air column. The phase locked loop devise is adopted for stability of the resonation and frequency.

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