General Machine Products RD7000 Traceable Rod Detection - Manual (Page 32)

26 RD7000 Operation Manual
7.4.5 Locating and tracing a sonde
Insert the sonde in the drain or duct access and locate
it while it is still just in view at the drain or duct entrance.
Hold the receiver vertical directly over the sonde with
the antenna in line with the sonde. Adjust the receiver
sensitivity so the bar graph reads between 60% and 80%.
The sonde radiates a peak field from the center of its
axis with a ghost signal at each end of the peak. Move
the receiver a little way behind and then in front of the
axis of the sonde to detect the ghost signals. Finding the
two ghost signals positively confirms the locate. Reduce
the receiver sensitivity to lose the ghost signals but still
indicate a clear peak response directly over the sonde.
Receiver sensitivity is now set for tracing the duct or drain
unless the distance between sonde and receiver changes.
Propel the sonde three paces along the drain or duct and
stop. Place the receiver over the supposed position of the
sonde. Do not adjust the sensitivity level.
Ghost Ghost
Figure 7.6: Sonde deployment
Figure 7.7: Locating a sonde
To locate a sonde:
Move the receiver backwards and forwards and
stop when the bar graph indicates a peak. You
can use the LCD compass to orient the blade of
the receiver with the direction of the sonde.
Rotate the receiver as if the blade is a pivot. Stop
when the bar graph indicates a peak.
Move the receiver from side to side until the bar
graph indicates a peak.
Repeat 1, 2 and 3 with the antenna vertical and
resting on or just above the ground. The receiver
should then be directly above the sonde with the
antenna inline with it. Mark the position of the
sonde and its direction.
Propel the sonde a further 1 or 2 meters, pinpoint,
and mark the position. Repeat this pinpoint
procedure at similar intervals along the line of the
drain or duct until the survey is completed.
1.
2.
3.
4.
5.
7.4.6 Checking sonde depth
The RD7000 receiver will automatically display the depth
of a located sonde providing the receiver is correctly
oriented and positioned above the sonde.
A B
d=0.7AB
d
Figure 7.8: Calculating sonde
depth
Pinpoint the sonde. Move the receiver in front of the
sonde and still with the antenna in line with it, increase
sensitivity to find the peak of the ghost signal. Move the
receiver to behind the sonde ensuring that the receiver
blade is always in line with the sonde. Find the null
positions A and B (See Figure 7.8). Measure the distance
between them and multiply by 0.7 to give an approximate
depth measurement.
Calculation method