7
Bad Signal:
Rotate the receiver
until it aligns
Good, Aligned
Absolute Signal
Locating a Sonde
Hold the receiver antenna directly above and in line with the Sonde, as shown
below. The receiver sensitivity needs to be adjusted for a meter reading indica-
tion between 60% to 80%.
The radiation pattern of the Sonde is shown below. The PEAK signal is when
the receiver is held directly over the Sonde with the antenna in line with the
Sonde. Both Ghost signals can be located behind and in front of the Sonde. By
locating the ghost signals, the user is confirming the accuracy of the locate.
Start by following the suspected path of the pipe and use the RL8873 Locator
to locate the Sonde. Stop locating when the PEAK reading is found. Then
rotate the receiver as shown in the figure right. When pivoting the receiver, do
not change the vertical position. The receiver will indicate a PEAK when the
receiver antenna is in line with the Sonde. (Figure A)
Now move the receiver side to side (across the path of the pipe) as shown
right. When the PEAK if found, the receiver is directly over the Camera/Sonde.
Mark this location. Next, check for ghost signals in front of and in back of the
Sonde to confirm the location. (Figure B)
Depth Measurement of Camera Head or Sonde
Once the line has been located, the depth can then be found. Refer to the
figure below for a reference. Start by moving the receiver along the path
behind the Sonde with the antenna in line with the Sonde and find a NULL
between the PEAK ghost signals. Mark this point (A). Then move the receiver
along the path in front of the Sonde and find another NULL. Mark this point
(B). Next, measure the distance between these two points. The depth of the
pipe is 0.7 times the distance between the two points.
Ghost
Null
Peak
Null
Pivot the receiver so the
antenna rotates—not
changing the vertical
position
Distance between
A
and
B
times 0.7
equals depth of sonde.
Move the receiver side
to side and when a
peak signal is found, the
receive is over the sonde
Ghost
Null
Peak
Null
Ghost
Ghost
Pipe
Pipe
Side
Path
Figure A
Figure B