Siemens SIMATIC NET PROFIBUS Operations Instructions download pdf (Page 46)

Installation and Maintenance

5.7 LED Displays and Troubleshooting

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

40 Operating Instructions, 01/2013, C79000-G8976-C270-03

Notes:

For a valid measurement, that the partner OLM at the other end of the fiber-optic cable must

send normal PROFIBUS frames. This can be recognized by the LED display of the partner

OLM (see section 5.7.1).

The output

voltages at the measurement sockets are influenced by many factors:

 strength of the optical transmit power of the partner OLM

 ambient temperature of the optical transmitter and receiver

 attenuation of the transmission line

 transmission rate used

The measurement sockets are therefore not intended as a substitute for a calibrated level

measuring device with a calibrated light source. The value obtained only serves to classify

the received optical signals in 3 classes:

 good (normal operation, green) 5 V > U > 240 mV

 critical (optical link margin reduced, yellow) 120 mV ≤ U ≤ 240 mV

 bad (functionality not guaranteed, red) U < 120 mV

The measurement must be performed with a standard ungrounded and high-resistance

voltmeter. The internal resistance of the measurement sockets is approx. 30 kΩ. A

connection from the measurement sockets or of reference potential to the OLM housing is

not permitted.

When an OLM of the SINEC L2FO type series is connected, the OLM V4 LED level indicator

has no meaning. The measurement sockets cannot be used.

5.7 LED Displays and Troubleshooting

5.7.1 LED displays

Figure 5-13 LED displays on the front panel

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Siemens SIMATIC NET PROFIBUS Operations Instructions Page 46