Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 56 / 68

ST300 SPIDER
54
In Fig. 59 shows the results of testing the same cable,
but with an electronic device parallel-connected to
wires #2 and #8 that belong to different twisted
pairs . Comparison with the reference (Fig. 55) yields
the following differences:
1. Interaction in different twisted pairs is not the
same: the pair “1” - “2” exhibits somewhat stronger
inductance/capacitance interaction than the other three
twisted pairs.
2. Distances to anomalies with peak responses
in different “cross-pair” combinations of wires are
different: in all of those that include wires #2 and #8,
distance to the anomaly is smaller than distances to
the end of the cable in all the other “cross-pair” wire
combinations.
Fig.59
3. Interactions between wires from different twisted pairs are different: the “2” - “8” pair exhibits
the strongest interaction, exceeding that within twisted pairs. It may also be noted that electromagnetic
interaction in all the “cross-pair” combinations involving wires #2 and #8, is higher than in other “cross-
pair” combinations.
This situation requires testing the “2” – “8” pair from both ends (3.6.1).
The examples above deal with testing a cable consisting of twisted pairs. One may determine whether
such a cable is intact, based, among other things, on the structure of electromagnetic interactions
between its wires. However, other types of cabling, whether flat or round, do not exhibit such distinct
patterns of inductance/capacitance interaction as twisted-pair cables do.
In Figs. 60-62 the results of testing a segment of a round six-core cable are shown.
Fig. 60 shows the results of testing a cable consisting
of six ‘non-paired’ defect-free wires .
One may note that magnitudes of inductance/
capacitance interaction between the wires are not quite
the same for each pair. Therefore, when testing straight
(as opposed to twisted-pair) cabling, one should not
pay attention to such minor differences. The main
criteria for finding out whether the cable is intact will
be the distances to anomalies with maximum response.
For a defect-free cable, these distances should be
approximately the same, and correspond to the length
of the tested cable segment, as exemplified in Fig. 60.
Fig. 61 shows the results of testing the same cable,
yet with an electronic device series-connected to
wire #6 .
The pattern of electromagnetic interactions between
the wires is significantly different from the one shown in
Fig. 60. The interactions are greater in all combinations
involving wire #6. Besides, all such combinations reveal
an anomaly with peak response at a distance of 16m
from ST300’s connection.
This situation is typical for a series connection or
defect in one of the wires. All the combinations with
wire #6 should undergo testing from both ends (3.6.1).
Fig.60
Fig.61