> > > Twisted pair is a transmission line and subject to all the vagaries > > > of load matching and such. > > > > > > That cables impedance is not listed there, > > > > Yes it is. 120 Ohms. > > Resistance is NOT impedance, Andy. And I first read that as 1200 because > my screen is high res and the ohm sign looks like another 0 at first > glance, I mentaly threw that whole line out as being technically > impractical, written by someone who obviously did not understand > anything about transmission line theory. My bad for the miss read of > 120 ohms as 1200 ohms, but still the use of the word resistance renders > it null and void in my technical mind. If they meant impedance, they > should have written impedance. If the loads J dactor is 0, then they > would directly correspond, but that J=0 generally would be quite rare in > the real world. > > However, my comments about the load termination, in this case with a 120 > ohm resistor from wire to wire at the load end are still valid.
https://www.expertdaq.com/static/img/info/RS485-termination-120-ohm.gif I think the extra bias network to power rails is necessary to get correct level in between data is sent. > Properly done, thats taken care of in the rs485 interface in the device, > but you never know when some bean counter between the engineer and the > production line will delete that seemingly useless part as a cost saver. They save beans in the short but have to spend more of them later. By investing the beans in rather good fast growing soil they figured out they could return more of them later but still have some left for them self. ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
