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Profibus noise

Created by: harish at: 3/20/2008 3:29 PM (4 Replies)

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3/20/2008 3:29 PM	Rate (0)
harish Posts: 5 Rating: (0)	Hi It’s been a pain till now sorting our profibus noise problem in our plant from past 3 months. We have around 30 nodes “CUMC Drives” on 416-2DP network, off late we are observing numerous breakdowns because of bus faults. This bus faults are occurring randomly. On approaching siemens, they said - it is noise problem. But could not guide us on, what could be the exact problem. Could somebody from the forum, who has come across the same problem. Would be of great help. Regards Harish
harish Posts: 5 Rating: (0)
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3/21/2008 12:20 AM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Hello, well ... this is a tough one. I would start to investigate what could cause the drop outs. Is it happening on certain events... Is the grounding sufficient... would it help to add some Repeater or maybe even Diagnostics Repeater to device the Bus to certain Segments... Just to begin with. To go a step ahead you have to monitor the Bus with storage oscilloscopes to see how bad the spikes are... Than you may start to determine where to enforce shielding... or grounding or even try to use FO instead of CU. Just to think about... for you. Best regardsJ_Bell
J_Bell Posts: 5822 Rating: (412)
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3/24/2008 4:47 AM	Rate (0)
harish Posts: 5 Rating: (0)	Hello, well ... this is a tough one. I would start to investigate what could cause the drop outs. Is it happening on certain events... Is the grounding sufficient... would it help to add some Repeater or maybe even Diagnostics Repeater to device the Bus to certain Segments... Just to begin with. To go a step ahead you have to monitor the Bus with storage oscilloscopes to see how bad the spikes are... Than you may start to determine where to enforce shielding... or grounding or even try to use FO instead of CU. Just to think about... for you. Best regardsJ_Bell Hi Bell We reduced the baud rate from 1.5Mbps to 500kbps. The problem is suppressed for now, feel this problem couldre-occur again. I would connect a repeater in between two segments and increase the baudrate and get the speed back to 1.5Mbps. You suggested to check the spikes using a oscilloscope, could please guide me to a docuement which explains the same. Could you also guide me to a document which has shielding and earthing guidelines please. Regards Harish
harish Posts: 5 Rating: (0)
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3/24/2008 4:29 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Dear Harish, I hope I can provide you with some information. Here the Manual: SIMATIC NET PROFIBUS Networks It contains valuable information about wiring and grounding of PROFIBUS Networks. Sadly I have no manual for measuring PROFIBUS with an Oscilloscope. I know that you have to subtract the B wire to the A wire and if you let the Oscilloscope do the job you see the signal. I agree with you in the point that lowering the Baudrate will not solve the problem. It will come back absolutely sure... and than most probably in the most improper moment. I hope you will fix the situation. Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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3/25/2008 4:55 AM	Rate (0)
ylhj Posts: 25 Rating: (1)	Hi Harish, To investigate the Profibus network error, it is better touse a ProViewXL bus tester which can measures the signal quality/ voltage/trasmission rate/ ..etcfor each node. Normally the bus noise is come from hardware, so it would be suggested to check all Profibus connecter/ terminator/ cable/ termination status/ etc. The proper test tools will be more efficiently to locate the error.
ylhj Posts: 25 Rating: (1)
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