Distinguishing false signals in cable locating
AssigneeMerlin Technology, Inc.
InventorsJohn E. Mercer, Albert W. Chau
Life of this patent
Estimating the term…
Abstract
Discriminating between a cable locating signal and a false cable locating signal is described. A reference signal, which contains a locating signal frequency impressed on it, is transmitted in a way which provides for detection of a phase shift between the locating signal and the false locating signal. Based on the phase shift, a receiver is used to distinguish the locating signal from the false locating signal.
Claims13
A transmitter for use in a region which contains at least first and second in-ground cables, each of which cables includes an electrically conductive component such that, when the first cable is driven at a locating signal frequency to emit a locating signal in an electromagnetic form, the locating signal can be coupled to the second cable in a way which causes the second cable to generate a false locating signal in electromagnetic form, said transmitter comprising:
- a frequency generator configured to generate said locating signal frequency and to generate a reference signal, with said locating signal frequency impressed thereon;
- a telemetry transmitter configured to transmit the reference signal as an electromagnetic reference signal;
- and
- a coupler configured to couple the locating signal frequency onto the first cable such that detection of a phase shift between the locating signal and the false locating signal at a receiving location and based on the reference signal distinguishes the locating signal from the false locating signal.
In a region which contains at least first and second in-ground cables, each of which cables includes an electrically conductive component such that, when the first cable is driven at a locating signal frequency to emit a locating signal in an electromagnetic form, the locating signal can be coupled to the second cable in a way which causes the second cable to generate a false locating signal in electromagnetic form, an apparatus configured to discriminate between the locating signal and the false locating signal, said apparatus comprising:
- a transmitter configured to generate said locating signal frequency for coupling onto the first cable and to transmit a reference signal as an electromagnetic reference signal, which contains said locating signal frequency impressed thereon, in a way which provides for detection of a phase shift between the locating signal and the false locating signal;
- and
- a receiver configured to detect said phase shift and to distinguish the locating signal from the false locating signal based on the phase shift.
Dependencies are inferred from the claim text.