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A-12 – Siemens SIMATIC NET PROFIBUS User Manual

Page 252

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Testing PROFIBUS

A-12

PROFIBUS Networks SIMATIC NET

6GK1970-5CA20-0AA1 Release 2 05/2000

A.2.4

Checking the Optical Signal Quality with PROFIBUS OLM V3

The receive level of the two optical channels can be detected using a normal
commercially available voltmeter attached to measurement sockets on the
PROFIBUS OLM V3. The voltmeter can be inserted and removed during operation
using 2 mm laboratory test plugs (see Figure A-6).

Figure A-6

Testing the Signal Quality on an OLM V3 with a Voltmeter

This allows the following:

S

The incoming optical power can be documented, for example for later
measurements (aging, damage)

S

A good/bad check can be made (limit value).

The correlation between the measured output voltage and the signal quality is in
the form of a curve (see Figure A-7).