Rockwell Automation 1788 NetLinx Media Checker Users Manual - Manual (Page 18)

18 The Test Function (TEST)
1788-UM002A-US-P – April 2000
Table 9. DeviceNet Test Failures (without Cable ID)
Display Failure Description
The MediaChecker detects a
very high resistance between the
data lines and the “-” power line. “FAULT” and “350
Ω
“ are blinking. There is probably
one or more I/O device connected to the cable under
test. To determine the cable length, do one of the
following:
•
Disconnect the I/O devices and retest the cable.
•
Install a terminator at the far end of the cable,
measure the resistance of the cable in series with
the terminator; then calculate the cable length. See
“Calculating the Distance to a Short” on page 32.
The MediaChecker detects a
fairly high resistance between
the CAN_H and CAN_L (data)
wires. “FAULT” and “OPEN” are blinking.*
A terminator is probably connected to one end of the
bus. You can subtract the resistance of the terminator
(typically 120
Ω
) from the measured resistance, then
calculate an approximate length using the remaining
resistance. See “Calculating the Distance to a Short”
on page 32.
To determine the cable’s wire map and get a more
accurate length measurement, replace the terminator
with the Cable ID and run the test again.
* Because some measurements are not possible on faulted cables, the MediaChecker might report the + and – wires as open when they
are not actually open.