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???
01/09/08 16:00
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 		 #149194 - Have you seen...
Responding to: ???'s previous message
...how they transmit the RS485 bus ground?? Over the shield, which is connected to signal ground via 100Ohm resistors! So, interference and ESD hitting the cable shield is shifting the common mode potential! These 100Ohm isolating resistors is an entirely old fashioned methode to prevent hum loops. Introducing impedances in the cable shield is very bad design practise and is nearly a guarantee to fail the CE tests.

More, ESD hitting the cable shield is injected directly into the isolation barrier.

Hardly a reliable methode. PROFIBUS people must have had good reasons to implement their grounding and shielding scheme.

Kai

List of 27 messages in thread
TopicAuthorDate
galvanic isolated communication            01/01/70 00:00      
   What is domotica?            01/01/70 00:00      
      Domotica            01/01/70 00:00      
         GND loop wont be a problem            01/01/70 00:00      
            Misunderstanding?            01/01/70 00:00      
               RS485 Isolators            01/01/70 00:00      
      Transformers vs. optocouples ?            01/01/70 00:00      
         there are galvanically isolated 485 transcievers            01/01/70 00:00      
   PROFIBUS?            01/01/70 00:00      
      I would not            01/01/70 00:00      
         Have you seen...            01/01/70 00:00      
            no, I have not and I definitely would not            01/01/70 00:00      
         RS485            01/01/70 00:00      
   Fibre optics?            01/01/70 00:00      
      Yes, there is, but rather expensive!            01/01/70 00:00      
   Wireless?            01/01/70 00:00      
   Power-line communication?            01/01/70 00:00      
   Standard Radio Uses Optoisolators            01/01/70 00:00      
      Shield            01/01/70 00:00      
         noibody said not to ground cases etc            01/01/70 00:00      
   Isolated RS485            01/01/70 00:00      
   Jeroen, where are you??            01/01/70 00:00      
      please do not answer Jeroen, where are you??            01/01/70 00:00      
         ???            01/01/70 00:00      
            Kai            01/01/70 00:00      
               But he did already!            01/01/70 00:00      
   galvanic insulaton            01/01/70 00:00      

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