Adeel there is no such thing as the "receiver not supporting the common". The receiver most definitely has its common mode referenced to the negative supply rail. This is clear in any '485 receiver specification. You can answer your question by evaluating the loss and the allowable ground noise between the two points. Your limit will be set by when the signal either falls below the nominal 50mV receiver threshold, or the CM noise take you out of the CM range. Steve. At 07:02 PM 2/24/2005 +0500, Adeel Malik wrote: >Steve, > Using the ground signal wire keeps the common voltage range >within -7V to +12 V, that of course improves noise immunity as well as >reliability. But the point is that if the slave device doesn't support >the ground signal connection, then up to how much distance the Master >can transmit the data reliably at 57600 baud rate over RS485 Network >without that ground wire. > >Adeel > >-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >On Behalf Of steve weir >Sent: Thursday, February 24, 2005 6:40 PM >To: adeelmk@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: Necessity of Ground signal for RS485 transmission >at 500 ft cable length > >Adeel, RS485 is not galvanically isolated. Think receiver common mode >range. > >Steve. >At 06:24 PM 2/24/2005 +0500, Adeel Malik wrote: > >Hi All, > > Can someone comment on the need of separate Ground Signal > >Wire in addition to the standard 2-wire RS485 Connections between the > >Master and Slave device. I have come to know that separate Ground wire > >b/w the two devices communication via RS485 at higher baud rates and > >increased cable length improves signal transmission. > >Regards, > >Adeel Malik > > > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to: > >http://www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: > > http://www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > > >The weirsp@xxxxxxxxxx e-mail address will terminate March 31, 2005. >Please update your address book with weirsi@xxxxxxxxxx > > >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >http://www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: > http://www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > The weirsp@xxxxxxxxxx e-mail address will terminate March 31, 2005. Please update your address book with weirsi@xxxxxxxxxx ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu