| 摘要 |
PURPOSE:To measure the length of buried piping accurately by sending a sound wave into the buried piping from an entrance end and measuring the arrival time of the sound wave from the entrance end to the exit end. CONSTITUTION:A speaker 5 is connected to the entrance end 1a of the buried piping 1 and an oscillator 3 and an amplifier 4 are operated to send the sound wave into the piping from the speaker 5. Further, microphones 6 and 7 are installed at the entrance end 1a and exit end 1b and variation in sound pressure is detected and inputted to a time difference meter 10 through amplifiers 8 and 9 to knot the arrival time difference of the sound wave by the time difference meter 10. This time difference corresponds to the propagation time of the sound wave from the entrance end 1a to the exit end 1b and this time is multiplied by a sound velocity to find thelength of the piping. Even if there is a corrosion hole, different-diameter part, etc., in the middle of the buried piping 1, a secure, disturbance-free length measurement is taken with an about 1% error. |
