| 摘要 |
PROBLEM TO BE SOLVED: To detect a tube joint, provided in a hidden place of soil or the like, with high accuracy by connecting tube joint detecting impedance elements to both end parts of a heating wire in an electricfusion-welded tube joint provided with the heating wire inside or on the inner surface of a tube joint body made of thermoplastic synthetic resin. SOLUTION: When an oscillation start command signal is supplied to an oscillating circuit 28 from a control circuit 38 through a line 39, the oscillating circuit 28 generates burst wave, so that electromagnetic field energy from a transmitting coil 27 is supplied to a tube joint device 20 and also supplied to a receiving coil 35. Receive waveform can therefore be obtained from the output of the receiving coil 35. When the excitation driving of the transmitting coil 27 is suspended, the electromagnetic field energy decreases with the lapse of time, and at this time, output obtained from the receiving coil 35 also decreases. A plurality of peak-to-peak value are therefore obtained by a level detecting means 37, and a place where this peak-to-peak value becomes the maximum is detected as the buried place of the tube joint device. |
