| 摘要 |
PURPOSE:To easily measure the length of various linear or coil-like tubular bodies with high accuracy by measuring the propagation time required for a fact that an acoustic wave passes through air in the tube and arrives at the other end from one end. CONSTITUTION:An oscillator 2 consisting of a loudspeaker of a wide band, etc., is provided on one side of a tubular body 1, converts an electric signal from a frequency setting device 8, which has passed through a transmission strength amplifier 9, to an acoustic wave having prescribed transmission strength, and transmits it into the tubular body 1 for a prescribed time. A receiver 3 consisting of a microphone or the like is provided on the other side of the tubular body 1, receives an acoustic wave which has been propagated through air in the tubular body 1 and converts it to an electric signal and outputs it. The acoustic wave which has flowed into a tubular wall 1b does not become a noise in the other end of the tubular body 1, against the acoustic wave which has been propagated through air in the tubular body 1. A time counter 4 measures the propagation time required for a fact that the acoustic wave reaches the other end from one end of the tubular body 1, based on an amplified 10 receiving signal, and an acoustic wave generation timing signal from a controller 6, inputs it to a length computing element 5 and derives length of the tubular body 1.
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