RD4000 Locating System User Manual
Page 29
Sweep and search
There are a number of techniques available for locating unknown lines in an area. Use of these techniques is
particularly important before digging to ensure that buried lines are not damaged during digging.
Passive Sweep
•
Switch the receiver to power mode.
•
Adjust the sensitivity to maximum; reduce the sensitivity to
keep the bargraph on scale when there is a response.
•
Traverse the area in a grid search, at a steady walk, and
hold the receiver comfortably with the antenna in line with
the direction of movement and at right angles to any lines
that may be crossed.
•
Stop when the receiver 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 receiver 5cm/2in from the
ground and continue the sweep.
Switch the receiver to ‘Radio’ if the receiver has a radio detect mode. Increase sensitivity to maximum and
repeat the above grid search procedure over the area, pinpointing, marking, and tracing out any lines that are
located.
In most, but not all areas, radio mode will locate lines that do not radiate power signals and a grid search should
be made in both power and radio modes.
Sweep and search (inductive search)
An inductive search procedure is the most certain technique for locating
unknown lines. This type of search requires a transmitter and receiver
and two people. This type of search is referred to as a ‘two person
sweep’. Before starting the sweep, define the area of search and the
probable direction of lines crossing the area. The transmitter is switched
on in induction mode.
The first person operates the transmitter and the second person
operates the receiver. The transmitter induces a signal onto lines as it
passes over them and the lines are then detected with the receiver 20
paces upstream or downstream of the transmitter. Hold the transmitter
with its length aligned with the assumed direction of any lines.
The second person holds the receiver at the start of the area to be searched and with the receiver antennas at
right angles to the probable direction of the buried lines. Set the receiver sensitivity level as high as possible
without the receiver picking up any airborne signal directly from the transmitter.
When the transmitter and receiver are in line both operators start to move forward in parallel. The operator with
the receiver sweeps it backwards and forwards, keeping the receiver vertical, as he proceeds in parallel with the
transmitter. This method allows for misalignment of the transmitter, receiver, and buried line.
