© 2023 Radiodetection Ltd 45
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 RD8200SG 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 RD8200SG 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. CD frequencies
on both the locator and transmitter will be denoted by the
icon on the display.
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.
Locator
1 Press the key until the CD frequency is displayed,
indicated by the icon.
4 kHz CD
RD8200SG 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.
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