18
6
If the needle is at or close to the end of the meter scale, adjust the SENSITIVITY knob to bring
the needle back to the middle of the meter. (Decreasing the SENSITIVITY will give a sharper
Receiver response as you move closer to the target conductor.) Then move to a new position and
note the meter response. The meter reading will increase if the signal gets stronger (closer to the
conductor), or decrease is the signal gets weaker (further from the conductor).
7
Keep adjusting the SENSITIVITY knob and the position of the Receiver until you find a place
that gives a maximum reading. (This will occur when the Receiver forms an angle of 90 degrees
with the target conductor.)
4.5 Estimating the Depth of a Conductor
Follow this procedure to estimate the depth of a buried conductor:
1 Using the NULL method, find the exact location of the conductor. At a minimum distance of 35 feet
from the transmitter (to prevent air coupling between the transmitter and receiver), locate and mark the
conductor.
2 Then, still in the same mode of operation (NULL), tilt the Receiver to 45 degrees (aligning the bubble),
and move off to the side of the conductor. See Figure 4-5.
Figure 4-5: Estimating the Depth of a Conductor
3 When you "locate" the conductor a second time, with the Receiver at a 45 degree angle, mark the spot on
the ground. The distance between this second spot and the true location of the conductor (A), less the
distance between the center of the Receiver and the ground (B), is equal to the depth of the conductor (C).
See Figure 4-5.
4 Measurement accuracy is affected by the ratio of the conductor diameter compared to how deep the
conductor is buried. (The larger the pipe the less accurate the depth measurement.) Depth measurements
are also affected by soil conditions, overhead lines, and adjacent conductors.
