| 摘要 |
<p>PURPOSE:To enable a position of a joint to be detected in a short time by emitting a continuous wave which is frequency-modulated into a pipe which is buried under ground, receiving the reflection wave, and then receiving that reflection wave, mixing the continuous wave and the received reflection wave, and then detecting a beat frequency of both. CONSTITUTION:A continuous wave which is emitted from a ground surface 5 into a pipe which is buried under ground 4 is propagated under ground 6, is reflected by the pipe which is buried under ground 4, is received by a reception antenna 8, and is sent to a mixer 9. A beat frequency component of the continuous wave and the reflection wave is extracted from an output of this mixer 9 by a low-pass filter 10 and is converted into voltage signal. Then, while moving a ground surface 5 at an upper position (directly above) of the pipe which is buried under ground 4 along the pipe which is buried under ground 4, continuous wave is emitted, the reflection wave is received, a beat frequency of both is detected, and that beat frequency is converted into voltage signal and a reference signal is compared, thus enabling a position of a joint 4a of the pipe which is buried under ground where the distance from a ground surface 7 becomes shorter as compared with other parts.</p> |
