Completing The Circuit Path; Common Bond Conductors; Congested Areas - Metrotech 810 Line Tracer Operation Manual

1 When the Left/Right Guidance needle changes direction and the tone changes from broken to solid or solid to broken and the
Left/Right Guidance meter needle moves in the same direction as you are moving. (Normally, the Left/Right Guidance
needle moves in the opposite direction.)
2 The field strength reading will drop as you move toward the "ghost" conductor. (Normally, field strength would increase.)
3 If you take a depth measurement over a "ghost" conductor, you will get a random or illogical reading, or no reading at all.
The Receiver reads a "ghost" conductor when each coil on each side of the cross section of the antenna receives the same amount
of signal from two separate conductors.
The location of the "ghost" will vary, according to the soil conditions and the size, depth, and conductivity of any adjacent
conductors.
To re-establish the correct trace, backtrack and search the area in a 180-degree arc.

6.9 Completing the Circuit path

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 the jumper cable (refer to Figure 4-2). Attach each end of the jumper cable on opposite sides of the
insulator. (See Figure 6-1).
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. This makes it difficult to identify the target
conductor.
To verify you are tracing the targeted conductor, note the field strength and depth readings at a known location of the targeted
conductor. As you trace, any change in field strength or depth reading should be gradual. If either reading changes abruptly, you
are probably no longer over your targeted conductor.

6.11 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 and field strength 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:
Figure 6-1: Ground on Either Side of Trace Area
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