Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 57 / 68

OPERATING MANUAL
55
3.7. CABLE TRACING
Object of Search:
– tracing the cable routes in a facility (non-contact search);
– identifying the contacts of a cable in a junction box (contact search).
This is done in the “CABLE LOCATOR” mode of ST300 (2.4.2.2) with the aid of the Receiver (1.3.4).
Using ST300 in the “CABLE LOCATOR” mode on a powered line is strictly forbidden!
3.7.1. Cable Locator of ST300 in Use: Non-Contact Search
While checking cable lines in a facility, cable tracing may often be necessary, especially when the
cabling undergoing tests is embedded within walls, or laid behind non-removable panelling, or in cable
trunking that cannot be disassembled, etc.
Without special equipment, tracing cables may be very problematic.
With regular cable locators used in construction and decoration, one can trace straight cables, whereas
cables consisting of twisted pairs still pose a problem. The reason is that the operating principle of this
category of devices is based on the detection of magnetic field around the cable, and the magnetic
components of two wires in a twisted pair practically cancel each other out.
The cable locator of ST300 functions in a different way, detecting the electric component of the field,
so all kinds of low-voltage cables are traceable, including those consisting of twisted pairs. However, this
operating principle imposes certain limitations on the use of the cable locator of ST300. For instance,
tracing power mains cables is impossible.
Fig.62
Fig. 62 shows the results of testing the same cable,
yet with an electronic device parallel-connected
to the pair “1” – “6” .
As is seen from the figure, magnitudes of inductance/
capacitance interaction between wires have not changed,
as compared with Fig. 60, with the exception of pair “1”
– “6”, where the interaction is much stronger. Besides,
this pair reveals an anomaly with peak response at
16.5m from ST300’s connection.
This situation is typical for a parallel connection. The
pair “1” – “6” should be tested from both ends (3.6.1).
Fig.63
For a correct operation of the cable locator
of ST300,
– connect the line to be tested to the
Electronic Switch;
– connect the Main Unit of ST300 to the
ground of the power supply on site.
In the “CABLE LOCATOR” mode, a test signal
is sent onto one of the wires of the connected
cable. The cable is traced with the receiver
picking up on the field modulated with a two-
tone low-frequency signal. The Receiver unit is
equipped with both light and sound indication
(LED and inbuilt speaker) of the reception.
A three-position sensitivity control is also
provided.
When operating the Receiver, please make
use of the telescopic arm supplied with ST300.