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4.3 Route location methods
1.The Maximum method
This method consists of positioning the electromagnetic sensor in the direction of the magnetic
field created by the utility radiation (fig.4.3). EMD antenna must be positioned horizontally and
the sensor placed in a plane perpendicular to the cable route. In this case the maximum signal
level is observed when the sensor antenna
passes directly above the utility line. The
maximum method is intended for a quick
route location. Flat peaks of the signal
level curve do not allow for high location
accuracy, but enables a quick route
location.
The Maximum method
2. The Minimum method
When the EMD antenna in a vertical (transport) position is placed directly above the route
the signal is at its lowest level fig. 4.4. As the distance from the point directly above the pipeline
increases, the signal level first rises sharply then slowly decreases. This is the minimum method,
which is used to determine a more precise
route location (after quick route tracing
using maximum method.
The Minimum method
8. Set the required gain factor of filtered signal to
«×1/2/4/8», by pressing buttons ▲/▼
9. Commence detection or tracing according to the
method set in p.4.3, avoiding prolonged input/output
overloads
Horizontal
position
Vertical
position
7
Fig. 4.3
Fig. 4.4
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