17
Frequently Asked Questions
To set the VOP for more accurate length
measurements, see “Velocity of Propagation (VOP)” on
page 10. See Table 2 and Table 3 for the VOP values for
many cable types and conditions.
Maximum Length
The maximum length of cable that can correctly be
measured by the TS100 PRO is determined by several
factors. The most significant is the signal loss of the
cable itself. When the signal loss in a particular cable is
large enough, the tester cannot “hear” the TDR echo
and cannot determine the length of that cable. In this
situation, the tester displays -
Err
on the display. The
amount of signal loss in a cable is determined by the
characteristics of that cable and its length. The
maximum length shown in Table 2 is the length above
which the tester is not expected to be able to make a
valid measurement. For lengths above those stated in
Table 2, the tester’s accuracy is not specified.
Frequently Asked Questions
Q:
How do I calibrate or perform a self-test on the
tester?
A:
There are no adjustments inside the tester, and the
internal coating protects the critical components from
moisture and contaminants. There is nothing to
calibrate. The tester does a self-test every time you turn
it on.To do a self-test, turn the tester off then on again.
The tester will not lose any settings because it saves
settings in flash memory. The tester displays
8888
during the self-test.
Q:
Does it matter which clip lead I connect to which
wire in the cable under test?
A:
Not for any of the testing functions. However, when
you connect the tester to a cable, if you connect the red
lead first, an invalid reading may be displayed until the
full connection is made with both leads. The tester’s
TDR technology requires both leads be connected to
the wire pair or cable in order to determine its length.
While using only one of the leads is useful in tracing
cable position with the injected tone, both leads are
required to make valid length measurements.
Q:
What does the low battery indicator really indicate?
A:
The display shows
LO
and
bAtt
when the battery
voltage falls below 4.5 VDC (see Table 1), indicating
that you should replace the batteries. Although the
tester will continue to operate for at least 1 hour below
this voltage, some readings may be less accurate.
Q:
I tested an orange outdoor 25 foot (8 meter)
extension cord and the display read 19 feet (6 meters).
Is the tester broken?
A:
No. The accuracy of the reading is dependent on the
setting of the VOP. While the nominal setting for
general testing is
66
, the VOP for that kind of cable is
56
. To improve the accuracy of length measurements
for that or any cable, change the VOP as shown in the
instructions in the Velocity of Propagation section.
Q:
Why does the length reading sometimes change a
small amount when I open and short the far end of a
test cable?
A:
There are two causes. The first is that this is a
characteristic of the measurement technique used in
almost all low and medium cost cable length test tools.
In the case of the TS100 PRO Cable Fault Finder, the
variance occurs in only a few cable types and both
readings are within the specified accuracy of the
instrument. The second cause occurs when an
unshielded cable is coiled, as in a box or on a spool. The
magnetic field caused by the TDR signal itself couples
across to other parts of the cable and changes the
characteristics of the reflections.
