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6.8
Locating a Bend or Dead End
While tracing a line, you may find that the meter reading drops off suddenly, and that there is no
distinct reading when the receiver antenna is moved left or right. Stand in place and continue
sweeping the antenna from side to side but at the same time slowly pivot your body.
If you find a pivot angle at which the meter reading picks up again, it means you've located a
bend and can resume tracing in the new direction.
If you pivot all the way around (360 degrees), without getting any noticeable meter reading, it
means you've reached a dead end.
6.9
Valves, Manhole Covers, Tees and Risers
If the meter reading suddenly increases and then falls back while tracing a pipe you have
probably passed over a buried valve, manhole cover, tee, or riser.
6.10 Common Bonded Conductors
Telephone, power, and CATV sometimes use a common ground bond. If other conductors are
connected to your target conductor, putting a signal on the target can cause all the conductors to
carry the same signal, making it difficult to identify the target conductor.
To verify that you are tracing the targeted conductor, note the field strength at a known location
of the conductor. As you trace, any change in field strength should be gradual. If either reading
changes abruptly you are probably no longer over your targeted conductor.
6.11 Congested Areas
If you suspect that coupling from adjacent conductors is causing interference in the signal picked
up by the receiver try increasing the strength of the signal received from the transmitter and
decreasing the strength of signal from the interfering conductors by:
1. Changing to a different transmitter coupling point or coupling mode.
2. Improving the grounding connection or moving the grounding point.
3. Determine the location of the adjacent conductors. Then check to be sure that neither the
direct connect cable or the ground cable cross over any of the adjacent conductors. Re-
position them if necessary.
4. If you are using the Inductive (Indirect) mode, you may be able to decrease the amount of
interfering signal by changing the orientation of the transmitter to the targeted conductor.
Determine the location of the interfering conductor.
6.12 Pipes with Insulated Junctions
The high radio frequency signal of the VM-480B Pipe and Cable Locator will jump pipe insulators,
however, the signal will proportionately decrease each time it crosses an insulator. When
possible, such as when tracing a pipe with a meter, bypass the meter (insulator) by using a
jumper cable. Attach each end of the jumper cable on opposite sides of the insulator.
6 Tracing Factors and Helpful Information
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