Vop Variations - Fluke TS54 TDR User Manual

VOP Variations

Typically, cable manufacturers do not tightly control
the VOP of cables. The VOP of the same type of cable
from different boxes or from different manufacturers
can have large variations. Because the test set uses VOP
to calculate length, the accuracy of the length values
depends on the accuracy of the VOP setting.
For most applications, a length value that is calculated
with an incorrect VOP value is accurate enough to help
you find a fault on the cable. For example, opens often
occur at junction boxes. If the test set shows an open at
80 feet (25 meters), and you see a junction box at 70
feet (20 meters), you would first examine the wires at
the junction box.
But for some applications, such as when you measure
the remaining cable in a box, you must use a more
accurate VOP value. Tables 3 and 4 show VOP values for
specific cables and for other types of cable.
The VOP values in Tables 3 and 4 are for
unspooled, uninstalled cable. The VOP of a
cable can change if the cable is on a spool or is
installed near other cables.
Because the space and material between the
conductors can also change the VOP, length
values that the test set calculates with the
values in Tables 3 and 4 can change as much as
±5 feet (±2 meters) for cables that are the
maximum length.
Note
Table 3. VOP Values and Maximum Length for
Specifically Identified Cables
Maximum
VOP Length
64 2000 ft
(610 m)
63 1500 ft
(460 m)
61 2000 ft
(610 m)
60 1500 ft
(460 m)
58 1000 ft
(300 m)
66 2500 ft
(770 m)
68 2500 ft
(770 m)
72 2500 ft
(770 m)
67 500 ft
(150 m)
68 500 ft
(150 m)
57 500 ft
(150 m)
VOP Variations
Cable
Lucent 1024 006ABE 6/24
W1000, 6 pair CAT3 (Blue-
White)
BICC General Aerial
Service Wire (ASW) 2/22, 2
Pair Drop Wire
Superior Essex, 4 pair
CAT3 Plenum (not pair
dependent)
BICC General, 24 AWG
CMX Outdoor CMR
Station Wire
BICC General cross-
connect 24 AWG twisted
pair on original spool
Berk-Tek, CAT5 (Orange-
White)
Superior-Essex Cobra
CAT5 CMR (Orange-
White)
Superior-Essex Cobra
CAT5 CMP (Orange-
White)
Belden 88760 2 wire
shielded 18 AWG, Red-
Black
Belden 88760 2 wire
shielded 18 AWG, Red/
Black-Shield
BICC General, E22025,
Red-Black
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