In message <946f26262d1d3a43bc6b5114c624f26c1681253...@delvspr01.deltarail.com>, Andrew McCallum <andrew.mccal...@deltarail.com> writes >EN61000-4-5:1995 Figure 14 shows a EUT with a cable joining two EUT >having only one end of its shield grounded. For the test a 10nF >capacitor is connected at the ungrounded end to ground. > >Is shielding at one end every really necessary? I thought best practice >was always to shield both ends.
It is, but there are situations where large low-frequency currents can flow in shields grounded at both ends. A way to combat this without disconnecting the shield (always at the receiving end, so the source drives the cable capacitance directly) is to connect a thick conductor between the enclosures and keep it physically close to the shielded cable. However, the Figure is explicitly for testing a 'one end only' configuration. The 1995 edition is withdrawn, and the 2006 edition has a quite different Figure 14. -- This is my travelling signature, adding no superfluous mass. John M Woodgate - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
