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
>
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