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Bad Quality Reads using Simatic Net OPC

Created by: Marti9t9 at: 7/22/2013 12:20 PM (8 Replies)

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7/22/2013 12:20 PM	Rate (0)
Marti9t9 Posts: 5 Rating: (0)	Hi, Hope someone can help with a problem we are having at the moment. We have a project which consists of a redundant Simatic H station, a Simatic Net OPC server and a WinCC Scada. The problem is that while using the Simatic OPC server, we get ‘bad quality’ reads briefly each time we change the winCC scada screen. So what we see is a ‘Bad Comms’ msg in every field which is subsequently replaced by the actual value. This happens each time we change the screen. In our own custom OPC Client, we can see that the quality of the data is briefly bad and many fields are filled with a value of 32?? This happens even in Boolean fields. Then after 1 second, the quality returns to Good and the proper values are displayed. We know our Custom OPC client is not the issue because we have tried a different OPC Server and everything works fine. We have paid for the Simatic OPC server redunancy license however so we have to make this one work. Any help would be greatly appreciated. Martin
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7/23/2013 9:20 AM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, i don't think that this is an issue of the OPC server. I had the same reaction already seen. In this case an OPC Client wrote not allowed values to the specified OPC items. In this case the OPC server reported the last valuewith qualitybad to all clients. As i understand you right: Not all Items are going to BAD only the used one of the last Screen? Value 32 in ASCII Code a space and a space is for some items a not allowed value.Check if there is any script or setting how will cause this reaction.
Rated X Posts: 1547 Rating: (129)
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7/23/2013 12:05 PM	Rate (0)
Marti9t9 Posts: 5 Rating: (0)	Thank you for your reply. Interesting comment about the possible significance of the 32 value we see. You described that in your case an OPC client was attempting to write incorrect values to the items and the Server returned with a bad quality reading. This sounds reasonable, but we are not using a client to write values. We are only trying to display PLC values through the OPC to our WinCC Scada. With the exact same setup using a demo version of Kepware, the system worked flawlessly. No bad quality readings and the correct values appeared instantly when changing screens. I didn't understand this part of your response : "Not all Items are going to BAD only the used one of the last Screen". In terms of the WinCC, it can be considered that every field is displayed incorrectly for a brief moment but then updates with the correct value after a delay. This happens whether you have clicked on the screen previously or if its a new unopened screen. The OPC seems too slow to update when changing screen. I hope this information can help you understand our problem. Martin
Marti9t9 Posts: 5 Rating: (0)	Last edited by: Marti9t9 at: 7/23/2013 12:06 PM
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7/24/2013 8:56 AM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, this reaction seems to be a product feature. Please contact the support to create OPC Traces and let check the WinCC settings if there is any setting wrong. If any client will write or initialize some field it must be seen in OPC Traces which can be checked by product support. The problem with SIMAITC NET OPC Server is, that this server is communicating via Network to PLC which has also other things to do and not only communication. So SIMATIC NET takes much more time to respond with a value than Kepware with local items.
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7/24/2013 3:33 PM	Rate (0)
Marti9t9 Posts: 5 Rating: (0)	Thanks again for your input into this matter. As it happened I was investigating the OPC Trace files when i read your message. I think contacting support is the way to go too. Just for your information, I will share with you what i found within the log files. Please see attachments. In the first image (IVAROPC.txt) the Simatic Net cannot find a value in DB9 but my VAT table shows that in fact a value does exist there. The second image is a screenshot of the IVAROPC.1.txt file. We see hundreds of similar errors throughout this file. Lastly, as you mentioned, Simiatic Net is doing many other things is the background, therefore in the configuration console, I unchecked all the OPC protocols I don't need in the hope of speeding up response times. This didn't change anything unfortunately. If you had any more thought on this I'd love to hear them. Martin Attachment opcTrace_VAT.jpg (276 Downloads)
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7/24/2013 3:34 PM	Rate (0)
Marti9t9 Posts: 5 Rating: (0)	Second image.. Attachment IVAROPC1.jpg (264 Downloads)
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7/25/2013 1:33 PM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, i have never seen an empty OPC Item. Please check the length of your DB in PLC. This DB is a Global DB? Or is it an DB created by PLC Program (Create DB call)?
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7/26/2013 1:35 PM	Rate (0)
Marti9t9 Posts: 5 Rating: (0)	Hi, DB Lengths are fine. And yes the DB's are being created intially by SFC22 in the PLC program. That shouldn't cause problems though should it? Martin
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7/26/2013 2:26 PM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, it seems to be the problem. I don't know if it is allowed to use this type of DB for OPC communication. But if i compare the trace with the possibility, that the DB maybe isn't fully initialized by MC7 code it could be a reason. Is it possible to place a DB with maximum required length and disable the SFC122?
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