RS485 Length Restriction

derekm · Guest

Have an application where total line length would be slightly more than the recommended max. length of 4000' (but not by more than about 500 ft). Any experiece going beyond 4000 and how risky is it?

Thanks.

mimaroglu · New User Joined: 06 Jul 2010 Posts: 1

Hi, Can anybody explain the diffrance in 4000ft matter if the communication voltage of RS-485 uses ±140v instead of ±5v?

Guest · **Oct 19, 2011 2:53 pm**

Significantly dropping the signalling speed will take you to 1.5km but your noise margins may decrease.