| 摘要 |
D.C. voltage gradient ground level survey equipment for detecting protective coating defects in an underground pipeline beneath high resistance ground (such as bitumen/asphalt surfaces) has a pair of hand-held probe poles (11) with non-polarizing electrodes for measuring in-ground signals created by an injected pulsed signal; the probe poles are placed on the ground above the pipeline and are electrically and operatively connected to a receiver (12) carried by an operant; the poles being connected to a water reservoir carried in a back pack (13) worn by the operant by a water path (14) so that water is conveyed to pole tips which also have a grounding spike of stainless steel attached to increase conductivity when the probes are in contact with the ground; the amount of water conveyed to the pole tips is regulated by a hand valve in a tubing below the back pack (13) reservoir; a microswitch is installed in spring loaded handles of the poles (11) so that a voltmeter is de-activated whenever the poles are lifted up off the ground. |
