7 Tracing Techniques and Helpful Information
The circuit path between the point at which the Transmitter signal couples to the
conductor and where the Receiver is being held over the conductor has to be
complete. Otherwise, very little Transmitter signal will reach the Receiver. If you
suspect a break in the circuit path, look for disconnected leads, circuit breakers
and open switches. It is essential to provide a good ground when setting up the
Transmitter.
Power lines and telephone sheaths are assumed to be grounded. If the conductor is a
pipe which has an insulated joint, such as a gas pipe with a meter, use a jumper cable.
Attach each end of the jumper cable on opposite sides of the insulator.
7.10 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. This makes it difficult to identify the
target conductor.
To verify you are tracing the targeted conductor, note the current readings at a known
location of the targeted conductor. As you trace, any change in current reading should
be gradual. If reading changes abruptly, you are probably no longer over your targeted
conductor or have passed an intermediate ground point or “T” connection.
7.11 Congested Areas
In an urban or otherwise congested locate area, it is not uncommon for water, gas,
power, or telephone utilities to use common trenching. Every congested situation is
different; there are too many variables for us to cover here. Use good judgment and
locating skills to carefully determine where other conductors are in your locate area,
and what effect they may be having on your tracing situation. Make use of comparison
depth, field strength and current readings to determine and confirm that you are tracing
your targeted conductor.
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 connects 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. Place the
transmitter, turned on its end with the bottom facing the targeted conductor, over
the interfering conductor as shown below.
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