© 2015 Radiodetection Ltd
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Section 10 - Current Direction (CD)
10.1 Understanding CD
Current Direction recognition is a feature that helps to
positively identify a line at points distant from the
application of the signal. It is highly desirable, if not
essential, for positive identification of long distance lines.
These lines can be traced and positively identified
through congested areas or when running parallel to
other lines.
The CD feature on the RD8100PDL and PTL locators
indicate the direction of the current flow on a line. Identity
of the target line is established if the locator display
indicates that the current is flowing forward and away
from the point of application of the transmitter signal.
NOTE: CD mode is not supported on the RD8100PXL.
A signal that has coupled onto adjacent lines finds a
return path to the point of the original signal application.
This is indicated by the locator arrow pointing back
towards the transmitter.
This is in contrast to the forward pointing arrow indicating
the target line.
The CD transmitter signal should be directly coupled to
the target line with a remote ground connection. Most
CD signals are low frequency, making them unsuitable
for connection with a normal clamp or induction. These
can however be applied with a transmitter CD clamp.
Using Current Direction (CD) to aid
line identification
The RD8100 PDL & PTL locators, and Tx-10 and Tx-10B
transmitters feature several CD frequencies to help you
determine the direction of current through a target line.
NOTE: The transmitter and locator must both have the
same CD frequency or frequencies installed to enable
the feature to be used. If you have more than one CD
frequency installed ensure that the transmitter and
locator are both set to the same CD frequency.
Figure 10.1: Current Direction
To select the CD frequency, proceed as follows:
Transmitter
1 Switch the transmitter off
2 Connect the transmitter to target cable or pipe, either
by Direct Connection or by using a CD clamp
3 Switch the transmitter on
4 Press the
key until the CD frequency is displayed
CD is a combination of two frequencies, a CD frequency
and a locate frequency.
NOTE: RD8100 PTL locator models specific frequencies
are only supported by the Tx-10 transmitter model
Locator
1 Press the
key until the CD frequency is displayed,
indicated by the CD icon and two small arrows
above the frequency value.
4 kHz CD
The RD8100 PDL and PTL models feature Current
Direction using a 4 kHz frequency. This frequency is
designed to enable you to use CD to identify a target line
on higher impedance cables such as telephone cables
and CATV.
