Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 52 / 68

ST300 SPIDER
50
Fig.52
Fig. 52 represents a nonlinearity detection in a
8-wire cable with an electronic device connected
to it. The nonlinearity has been found on pair “4”–
“5”. The response is much stronger at the second
harmonic frequency than at the third.
As testing has been performed on an open-circuit,
one may safely assume that there is evidence of a
parallel-connected device that has semiconductor
components.
The absence of responses throughout the rest of the
table means that no electronics have been found
in parallel connection to any of the other two-wire
combinations.
Now test the cable in the short circuited configuration.
For the detection of electronics in series connection,
– with the Short-Circuiting Socket (23, Fig.1) short-
circuit all the wires of the tested cable at the far end;
– in the automatic mode, launch another scanning cycle
(“F4” button).
Upon completion of the testing cycle on all the two-
wire combinations, the table will be filled in with
graphic data on the reflection levels.
Fig. 53 shows the results of testing a 8-wire cable
that has an electronic device series-connected to
one of its wires. As is seen from the figure, all the
two-wire combinations involving wire #2 exhibit a
nonlinearity response. As all the wires are short-
circuited at the far end, it is safe to say that an
electronic device is series-connected to wire #2 of
the cable.
Fig.53
3.6. ANOMALY DETECTION IN A CABLE
Object of Search:
– detection of anomalies caused by unsolicited connections to a cable.
This operation is performed in the “REFLECTОMETER” mode (“REF”) specifically intended for testing
multiple-wire cables that consist of twisted pairs, although using it on other kinds of cables (two-wire and
multiple-wire straight) is also possible.
Two methods are essential to an efficient use of the “REF” mode:
– testing from both ends of the cable; this is done from the main screen of the “REF” mode (2.8.1) –
for the most part, when dealing with a two-wire cable, or a specific pair of wires in a multiple-wire cable;
– pair-by-pair comparison in the automatic “REF” mode (2.8.2) when testing a multiple-wire cable.
Using ST300 in the “REF” mode on a powered line is strictly forbidden!
The use of the Electronic Switch is required.
The tested line must be disconnected from any equipment at the far end. All known equipment must
be disconnected from the line.
If the line has any known branches, each segment must be disconnected from the main line and tested
separately (as the goal is to find unknown connections to a piece of cabling that is supposed to be free
from any connections at the time of testing).
It is advisable to perform testing on an open-circuited line.