Siemens SIMATIC NET PROFIBUS - Manual (Page 431)

8.4 Measuring sockets
35
8 Appendix
Version 1.0 8/00
8.4 Measuring sockets
Normal operation
0 100 200 300 400 500 600 700 800 900
Output voltage [mV]
Signal
quality
good
critical
poor
Reduced optical system reserves
Function not guaranteed
Diagram 1: Assignment of measured output voltage to signal quality.
Notes:
In order to attain a valid reading, it is necessary for the partner OLM at the other end of the optical fiber to send
regular PROFIBUS frames. This can be seen on the LED display of the partner OLM (see 5, ”LED Indicators and
Troubleshooting“, p. 25).
The output voltage at the measuring sockets is subject to many influencing factors, such as:
Ⅲ
the strength of the transmitting power of the partner OLM
Ⅲ
the ambient temperature of the optical sender and receiver
Ⅲ
attenuation of the transmitting link
Ⅲ
the transfer rates being used
The measuring sockets are therefore not intended as a substitute for a calibrated level measuring device with a
calibrated light source.
The readings taken should only serve to classify the optical signal being received in the 3 classes
Ⅲ
good (normal operation)
Ⅲ critical (reduced optical system reserves)
Ⅲ
poor (function not guaranteed)
Measurements must be taken with a conventional ungrounded and high-resistance voltmeter. A connection to the
OLM housing is not permitted either from the measuring sockets or the reference potential.