© 2023 Radiodetection Ltd 35
and its position is approximately known. Start with
medium output power from the transmitter, medium
frequency on the transmitter and locator, and Peak or
Peak+ mode on the locator.
Set the locator sensitivity to approximately 50% by
pressing the or key
NOTE: it may be necessary to adjust the sensitivity level
throughout the pinpointing to keep the bar graph on scale.
1 With the antenna perpendicular to the line, make
traverses across the line. Define the point of
maximum response.
2 Without moving the locator, turn it round as if it is on
a pivot. Stop at the point of maximum response.
3 Hold the locator vertical with the antenna just above
the ground and move the locator from side to side
across the line. Stop at the point of maximum
response.
4 With the end of the antenna close to the ground,
repeat steps 2 and 3.
5 Mark the position and direction of the line.
Repeat the steps of the procedure to increase pinpoint
accuracy.
If using Peak+ mode, switch to null arrows by pressing
and holding the key. Alternatively switch to Null
antenna mode.
Move the locator to find the Null position. If the position of
the Peak and the Null pinpoints correspond, it can be
assumed that the pinpoint is accurate. The pinpoint is not
precise if the marks do not correspond, but both marks will
show an error to the same side. True line position will be
close to the Peak position.
The line lies half the distance to the other side of the Peak
position as the distance between the Peak and the Null
positions.
6.7 Sweep and search
There are a number of techniques available for locating
unknown lines in an area. Using these techniques is
particularly important before conducting any excavation
work to help ensure that buried lines are not damaged.
Passive sweep
A passive sweep is used to locate Power, Radio, CATV or
CPS signals that may radiate from buried conductors.
To perform a passive sweep:
1 Press the key to select the passive frequency you
wish to locate. You can select from the following
passive frequencies:
Power
Radio
CATV (Cable TV)
CPS (Cathodic Protection System)
PASSIV (simultaneously detects Power and
Radio signals where present)
2 Adjust the sensitivity to maximum; reduce the
sensitivity to keep the bar graph on scale when there
is a response.
3 Traverse the area in a grid search, at a steady walk,
and hold the locator comfortably with the antenna in
line with the direction of movement and at right angles
to any lines that may be crossed.
Figure 6.4: Passive sweep
Stop when the locator response rises to indicate the
presence of a line. Pinpoint the line and mark its position.
Trace the line out of the area being searched. Resume
grid search in the area.
In some areas there may be a confusing amount of 50 /
60Hz power signals. Lift the locator 50mm / 2” from the
ground and continue the sweep, or use the key to
Figure 5.3: Pinpointing with Peak and Null indicators
Figure 5.2: Pinpointing a target line
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