English
C.A 6681 Cable locater
51
Note that, when breaks in multi-conductor cables are traced, all the other
wires of the cable or of the shielded conductor must be earthed. This is
necessary to prevent cross coupling of the applied signals (by a capacitive
effect) on the terminals of the source.
The earth connected to the transmitter can be an auxiliary earth, the earthing
terminal of a power outlet, or a correctly earthed water pipe.
When the line is traced, the place at which the signal received by the receiver
falls off suddenly is the location of the break.
Refine the detection by setting the power level transmitted by the
transmitter and the sensitivity of the receiver in manual mode.
3.2.3
LOCATING LINE BREAKS USING TWO TRANSMITTERS
When a line break is located using a transmitter supplying one end of the
conductor, its location may not be precise if conditions are unsatisfactory because
of a disturbance of the field. The drawbacks described above are readily avoided
by using two transmitters (one at each end) to detect line breaks. In this case,
each transmitter is set to a different line code, e.g. one transmitter to code F and
the other to code C. (The second transmitter, with a different line code, is not
included in the kit supplied and must therefore be purchased separately.)
Preconditions:
The circuit measured must not be live.
All unused lines must be earthed as shown in Fig. 12.
Connect the two transmitters as shown in Fig. 12.
The measurement method is identical to that used in §3.1 Getting started
If the transmitters are connected as shown in Fig. 12, the receiver will indicate C
to the left of the line break. If the receiver goes beyond the location of the break,
to the right, it will display F. If the receiver is placed right on the break, no line
code will be displayed, because of the superposition of the signals from the two
transmitters.
