© 2020 Radiodetection Ltd
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Section 9 - Current Direction (CD)
9.1 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 RD8200 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.
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 RD8200 locators, and Tx-10 and Tx-10G
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. CD
frequencies on both the locator and transmitter will be
denoted by the
icon on the display.
Figure 9.1: 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.
Locator
1 Press the
key until the CD frequency is displayed,
indicated by the
icon.
4 kHz CD
RD8200 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.
