I've read some material (a Jan Axelson article), that further confuses me on this matter of proper RS485 grounding for the shield that surrounds our twisted pair of data.
Like I say, I have always just grounded just one end to a good EARTH ground, either my transmitter or receiver, depending on the "best" ground available at either.
The xmtr for example may be mounted closer to an electrical panel with a ground rod nearby etc....so, that would be the preference.
But now, after reading the article, it is recommended that we use the
100 ohm resistors at each end, and these tie to SIGNAL GROUND. ! ? (as in power supply ground?).(My xmtr and rcvr both have a power supply ground that doesn't connect to earth ground).
for example....
xmtr signal ground > 100 ohm...........shield.............100 ohm < rcvr signal ground
She talks about how A and B need to referenced to ground but with long cable runs wouldn't you want to keep that doggone "antenna" isolated from the circuits?
Is she talking about the shield or another "third" wire?
Thanks very much -- I have to get this matter clear in my head.