RD5100H
2
O+ Operation Manual
34
© 2018 Radiodetection Ltd
9.2 CD reset
About CD reset
When you trace a signal on very long target lines, the
transmitter signal gradually bleeds into the ground by
capacitance. This means the phase angle of the
remaining signal gradually changes. A CD Reset can be
used to re-establish correct CD operation.
To perform a CD reset, press and hold the
key
This is referred to as phase-shift and can occur whenever
an alternating current signal is flowing in a system of
conductors that have a significant capacitance or
inductance. The relative phase angle between the two
frequencies will alter, but only over extended distances.
Figure 10.2: CD reset
Figure 10.2 illustrates a buried line with significant
capacitance to ground. It illustrates the gradual phase-
shift that occurs along the line. The diagram shows a
reference point on each waveform. At first, the reference
point occurs right on the Peak of a positive half cycle (A).
It gradually moves towards the zero crossing point (D)
and ends up on the Peak of a negative half cycle (F). The
direction has shifted from forwards to backwards. At the
intermediate point (D) the current flow cannot be
determined. At this point the CD arrows on the
RD locator will flash on and off. In the example
shown in the illustration, by returning to (C) which is the
last point at which a CD reading was achieved, and
performing a CD reset, the response at (C) will be
equivalent to that of (A).
In most cases the phase angle shift does not occur until
many kilometers from the transmitter and in some cases
a CD reset may only be required every 20 kilometers (15
miles).
Performing a CD reset
You should perform a CD reset every time you select a
CD frequency. CD reset can only be performed when in
CD mode.
To perform a CD reset:
While using any CD frequency,
1 Press and hold the
key
Alternatively
1 Press the
key to enter the menu
2 Scroll to the
CDR
menu using the
or
keys
3 Press the
key to enter the CDR menu
4 Press the
key to reset CD and exit to the main
menu