Rockwell Automation 1788 NetLinx Media Checker Users Manual - Manual (Page 27)

Measuring Cable Length (LENGTH) 27
1788-UM002A-US-P – April 2000
Measuring Cable Length (LENGTH)
Important: If you suspect inaccurate length readings,
calibrate the MediaChecker to the cable. See
“Calibrating the MediaChecker to a Cable” on
page 10.
Length measurements show the total length
of the trunk plus all drops or taps on the
cable. For information on calculating the
length of just the trunk, drops, or taps, see
“Calculating Trunk, Drop, or Tap Lengths” on
page 29.
Using the MediaChecker's LENGTH function, you can
measure the length of both twisted-pair and coaxial
cables. If the MediaChecker is not calibrated to the cable
under test, the factory defaults are used to compute the
length. If you require more accurate length
measurements, refer to “Calibrating the MediaChecker to
a Cable” described on page 10.
Before a length measurement is made, the MediaChecker
performs diagnostic tests to prevent any cable failures
from corrupting the length measurement. All failures are
described in the earlier sections “The TEST Function” and
“Testing the Wire Map”.
To measure the length of a cable, do the following:
1. Disconnect all network equipment and remove the
terminator from the far end of the cable to be tested.
(For information on calculating the length of a
terminated cable, see “Calculating the Distance to a
Short” on page 32.)
2. Connect the cable under test to the appropriate
connector on the MediaChecker.
3. Turn the rotary switch to LENGTH.
You can omit step 4 if you know that the cable
selection is correct for the cable under test.