Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. And not using the shield as a conductor is useful because any current flow in the shield would cause magnetic noise to be induced in the conductors along inside the cable. Even in power cables, grounding both ends of the shield may cause ground loops,resulting in mains frequency currents (formerly: hum) that are hard to locate. Generally, magnetic noise is harder to fight than electrostatic.
Peter Am 16.03.2015 15:41, schrieb Steve Stallings: > I would recommend that shielded signal cables have the > shield grounded only at the end where the signals are > consumed. > > If a ground is needed by the device at the end of the > cable, you should use a conductor inside rather than > the shield itself. > > If there are signals going both ways, provide the shield > ground connection at the end where the most sensitive > signals are consumed. > > The purpose of grounding only one end of the shield is > to prevent current from flowing in the shield itself and > distorting the signals due to electromagnetic coupling. > > A shield is primarily intended to prevent electrostatic > coupling from the outside world. > > If the cable does not contain sensitive signals, such as > the power cable from a VFD to the spindle, then it is > acceptable to ground both ends of the shield. > > Steve Stallings > www.PMDX.com > > >> -----Original Message----- >> From: Matt Tucci [mailto:[email protected]] >> Sent: Monday, March 16, 2015 7:54 AM >> To: Enhanced Machine Controller (EMC) >> Subject: Re: [Emc-users] VFD causing limits to trip. Huh? >> >> Are the shielded wires only grounded at one end and at the >> controller end? >> >> On Sun, Mar 15, 2015 at 1:22 PM, Karlsson & Wang < >> [email protected]> wrote: >> >>> I think grounding is the most important. There are normally >> --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. http://www.avast.com ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
