Allen-Bradley MediaChecker 1788-MCHKR Manual page 18

18
The Test Function (TEST)
Display
* Because some measurements are not possible on faulted cables, the MediaChecker might report the + and – wires as open when they
are not actually open.
1788-UM002A-US-P – April 2000
Table 9. DeviceNet Test Failures (without Cable ID)
Failure
The MediaChecker detects a
very high resistance between the
data lines and the "-" power line.
The MediaChecker detects a
fairly high resistance between
the CAN_H and CAN_L (data)
wires.
Description
"FAULT" and "350Ω" 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.
"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.