Rockwell-automation 1788 NetLinx Media Checker Users Manual Manual de usuario descargar pdf (Pagina 22)

The Test Function (TEST)

1788-UM002A-US-P – April 2000

Table 10. ControlNet Test Failures

Display Failure Description

The MediaChecker detects a cable length

greater than 2130 ft (650 m)

, which is the

maximum it can measure.

If “2130'“ (650 m)

is flashing, the cable is

longer than the maximum the

MediaChecker can measure. Break the

cable near its center and measure the two

parts separately.

The MediaChecker detects a resistance that

is greater than the resistance of 2130 ft

(650 m)

of cable (about 65 Ω).

A terminator resistor is probably connected

to one end of the bus. Remove the

terminator; then retest.

Or, subtract the terminator’s resistance

(75 Ω) from the measured resistance to get

the cable resistance. Then use the

procedure under “Calculating the Distance

to a Short” on page 32 to calculate the

cable length.

The MediaChecker detects a resistance that

is less than the resistance of 2130 ft (650 m)

of cable (about 65 Ω).

“SHORT” is blinking. A resistance less than

65 Ω (which is too low to be a terminator) is

across the line.

The display shows the most likely distance

to the fault.

1. The MediaChecker measures lengths to 650 m; however distances in feet beyond 999 ft are rounded to the nearest 10 ft.

2. A short greater than zero ohms causes the MediaChecker to display a length greater than the actual distance to the short. Figure 4

on page 23 illustrates this process using an Ethernet example. The MediaChecker uses ohms/foot to calculate distance to a short.

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Rockwell-automation 1788 NetLinx Media Checker Users Manual Manual de usuario Pagina 22