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rs485 ground issue.....?

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jit_singh_tara

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let there be two systems


1. controller and max485 as transmitter -> twisted pair cable.

2. twisted pair cable ->max485 receiver -pc .

i waqnt to know how does max485 receiver recognise the voltage levels without a ground connection , transmitter and receiver have separate grounds.
will it work....
 

here is a nice article that should more-the-less clarify the issue of two different grounds ..
"Understanding Common-Mode Signals"
**broken link removed**

the best thing you can do is to optically isolate both sides and the different ground issue is gone -> forever ..

rgds,
ianp
 
Although RS485 doesn't need to recognize the voltage levels but the voltage difference only and further have to met the common mode requirements, RS485 cabling without isolation usually has a ground with the signal, may be the cable screen used as a ground.
 

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