10
TS90 Cable Fault Finder
Users Guide
Velocity of Propagation (VOP)
VOP is a cable specification indicating the speed at which a
signal travels down the cable. A VOP of 66 means the signal
travels at 66 % of the speed of light. The tester uses VOP to
calculate cable length. See “Time Domain Reflectometry
(TDR) Technology” on page 19 for details.
Here are some important points about VOP:
Different cables have different VOP settings.
The tester’s default VOP setting of 66 is suitable for most
applications.
Using the VOP specified for a cable ensures the most
accuracy in fault location, length measurements, and
inventory management. Table 2 and Table 3 show VOP
values for common cables. Some common VOP values
are also listed on the tester’s battery door.
You can set the tester’s VOP to a known value, or you can use
the tester to determine the VOP for a known length of
cable.
To set the VOP to a known value:
1
Turn the tester on while holding down the
UP
or
DOWN
button. In this mode, the display alternately shows the
VOP setting (
-VV-
) and the calculated length
(LLLL
).
2
When the VOP setting is displayed, press the
UP
or
DOWN
button. This keeps the VOP value on the display
for adjustment.
3
Use the
UP
and
DOWN
buttons to set the VOP to the
desired value.
4
To exit the VOP adjustment mode, turn the tester off.
