English
C.A 6681 Cable locater
61
3.3.4
DETECTION OF RATHER DEEP UNDERGROUND CIRCUITS
The magnetic field produced by the signal from the transmitter is strongly
conditioned by the shape and size (area) of the loop formed by the "forward"
conductor (connected to the "+" of the transmitter) and the "return" conductor
(connected to the other terminal of the transmitter).
For this reason, in two-pole applications on a multi-conductor cable (for example
3x1.5mm²), the depth of detection is severely limited. Since the two conductors
are very close together, the area of the loop is often insufficient.
In this case, it is best to use an "auxiliary" conductor, not one of the conductors of
the multi-conductor cable, for the return path.
The important point is that the distance between the "forward" conductor and the
"return" conductor should be greater than the depth underground, and in practice
this distance is routinely at least 2m.
Preconditions:
The circuit must be dead;
Connect the transmitter as shown in Fig. 21;
The distance between the supply line and the loopback line must be at least
2~2.5m;
The measurement method is identical to that used in §3.1 Getting started
Fig.21
Remark:
In this application, the influence of the moisture in the floor or wall on the
depth of detection is negligible.
