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Kai Klaas
11/10/06 09:18
  11/10/06 09:19

Read: 622 times

#127720 - Yes, crossed opinions...
Responding to: Erik Malund's previous message
Erik said:
I think Kai and I have crossed opinions

Yes, but I don't want to start a "war"...

Erik, what we discuss is discussed between engineers for decades, right? There are two main groups, one sitting in the USA demanding the use of unshielded cables, protecting the signals by filters etc. and the other group is sitting in the EU demanding the use of shielded cables, with shields connected to chassis ground at both ends, in the last consequence.

PROFIBUS applications, which carry RS485 signals have specifications which demand to use shielded cables with both ends connected to chassis ground, which is finally connected to protective earth everywhere. The RS485 signal lines is galvanically isolated from the cable shield. There's only a 10nF cap bewteen both, to shunt high frequency noise to protective earth.

It's not so much, that the one scheme is better than the other (ok, I'm convinced that the shielded cables with chassis connections at both ends is better...). Problematic is more, that both schemes cannot be mixed! You either omit ground loops totally or you have an infinite number of them to make the introduced ground loop potentials to cancel each other.


List of 20 messages in thread
Lightning protection      Ap Charles      11/08/06 06:17      
   there is much to this      Erik Malund      11/08/06 06:19      
      Lightning protection      Ap Charles      11/08/06 06:24      
         so doesa EMI      Erik Malund      11/08/06 06:36      
            Mr. Faraday knew how...      Kai Klaas      11/08/06 08:13      
               THICK metal      Steve M. Taylor      11/08/06 09:45      
            Direct Hits      Russell Bull      11/08/06 17:06      
               Keep it out of the encosure!      Kai Klaas      11/08/06 20:08      
                  My pplication      Ap Charles      11/08/06 23:52      
                     Details?      Kai Klaas      11/11/06 08:33      
               I disagree      Erik Malund      11/09/06 06:07      
                  No, no...      Kai Klaas      11/09/06 20:32      
                     Disconnecting the shield at one end of the cables      Ap Charles      11/09/06 23:44      
                        a) and b)      Erik Malund      11/10/06 06:05      
                           Yes, crossed opinions...      Kai Klaas      11/10/06 09:18      
                              and the twain shall never meet      Erik Malund      11/10/06 10:52      
                        the Shield      Andy Peters      11/10/06 14:55      
                           The RS485 signal lines is galvanically...........      Ap Charles      11/10/06 23:01      
                              GND of RS485 bus, PROFIBUS      Kai Klaas      11/11/06 08:27      
   If you get this close        Jez Smith      11/09/06 01:28      

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