Erratic process image from ET200B

[MartinW]

We have a S5 928B Processor, with an IM308B ET200 card. The profibus network has a 16I/16O ET200B IO module, an OP15, and a profibus Festo valve island.

The problem that we are seeing is that the inputs on the ET200B module - despite showing as constantly ON on the module LEDs - appear on a PG as zeros for most of the time, with an occasional flash of their actual values.

We have replaced the ET200B module, and its base. We have also removed the existing profibus cable from the ET200B module and IM308B. We put a test profibus cable between the IM308B and a replacement ET200B module with the same profibus address. A signal was put into one of the inputs of the replacement module, and when observed through the PG, that input displayed the same behaviour as previously seen. The input showed as a 0 with an occasional flash of its true value, a 1.

None of the other inputs on this profibus network (specifically from the Festo module) show this behaviour.

Rewiring the problem inputs into unused input cards on the main rack resolved the issue, insofar as we were able to get the machine running again, but the problem remains unresolved.

Any ideas what might be causing this please?

thanks,

Martin

 

[KalleOlsen]

Here, check the troubleshooting chapter thoroughly:
http://www.pacontrol.com/download/PROFIBUS_Guideline_Commissioning.pdf

And Profitrace is a super helper:
http://www.procentec.com/profitrace2/index.php

Kalle

 

[MartinW]

Here, check the troubleshooting chapter thoroughly:
http://www.pacontrol.com/download/PROFIBUS_Guideline_Commissioning.pdf

And Profitrace is a super helper:
http://www.procentec.com/profitrace2/index.php

Kalle

Hi Kalle,

Thanks for the information. I'm making enquiries regarding the Profibus analysis tool.

Siemens said to me that because this was "old" Profibus L2 (via IM308B card) that there was no diagnostic information that could be got from the bus. Is this not correct?

thanks

Martin

 

[KalleOlsen]

Sorry, but I haven't worked with L2 the last 15 years so I have no fresh experiences to share. I can remember there was an FB that could read out status from the 308; if nodes were defined and if they were accessible on the bus. It wouldn't help you much with this mysterium.

Sinec L2 is the mother of Profibus DP, also running RS485, so the Profibus troubleshooting guidelines should be relevant here also. The issues with reflections, retransmissions, common offset error, grounding, signal voltage levels, line lengths, screening, EMC, and... are also close related, so the Profitrace should be suited. But better check with the dealer.

Kalle

 

[finnland]

Arron, it is better for you to start a new topic if you want to get a quicker response for your question.