Monitoring - ABB RLM01 Inbetriebnahmeanweisungen

Monitoring

4 Monitoring
16
The LEDs assigned to lines A, B and M on the front panel are used to indicate bus
activity (Act) and possible errors (Err) on the PROFIBUS lines. The monitoring logic
in RLM 01 assumes that lines A & B are used for communication during operation. If
it is subsequently possible to receive data over only one of the two lines, the non-
available line is reported as faulty. If the redundant (second) line also fails, the same
state results for the monitoring logic as for a redundant PROFIBUS link A AND B
that is not in operation at all. Since the logic has no criterion for making a distinction,
no error message is generated by RLM 01. The alarm contact remains closed and
the two Act and Err LEDs are unlit. But the condition just described does not go
undetected. In this case the PROFIBUS master generates the error message, since
it cannot access the slaves either via line A or line B.
An Err LED flashing at an undefined pulse/pause ratio indicates that the line in ques-
tion has failed AND that there is only sporadic data traffic on the redundant line.
The monitoring logic can only indicate operating and error states correctly if the
baud rate is set correctly.
RLM 01 also tests whether the supply voltage is present at inputs L1+ and L2+. A
single power supply with L1+ alone always requires a cable jumper from L1+ to L2+
(see Chapter 3). This prevents an unwanted error message.
3BDD011600R05