Rockwell-automation 1788 NetLinx Media Checker Users Manual Manuel d'utilisateur télécharger pdf (Page 19)

The Test Function (TEST)

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.

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.

“SHORT”, ≤954' (291 m), and “OPEN” are blinking.

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.

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Rockwell-automation 1788 NetLinx Media Checker Users Manual Manuel d'utilisateur Page 19