Rockwell Automation 1788 NetLinx Media Checker Users Manual - Manual (Page 19)

The Test Function (TEST) 19
1788-UM002A-US-P – April 2000
Table 9. DeviceNet Test Failures (without Cable ID) (cont.)
Display Failure Description
The MediaChecker detects a low
resistance between the CAN_H
and CAN_L (data) wires;
however, the resistance is higher
than a short circuit. “FAULT” and “OPEN” are blinking.
1
There is a resistive fault between L and H. The
resistance is higher than the resistance of a cable
1640 ft long (500 m), which is the maximum allowable
length.
The MediaChecker detects a low
resistance between the CAN_H
and CAN_L (data) wires.
2
“SHORT”,
≤
954' (291 m), and “OPEN” are blinking.
1
There is a short between L and H. The MediaChecker
displays the most likely distance to the fault.
Connect the Cable ID to the far end of the cable and
repeat the test to check the + and – wires.
1. Because some measurements are not possible on faulted cables, the MediaChecker might report the + and – wires as open when
they are not actually open.
2. A short greater than zero ohms causes the MediaChecker to display a length greater than the actual distance to the short. See Figure 4
on page 23. The MediaChecker uses ohms/foot to calculate distance to a short.