Rather than 'ground', perhaps 'RF return' or 'counterpoise' might be better terms?
I think the thing that makes EMC mysterious is that the complete RF circuit is unseen and difficult to accurately define, given all the parasitic elements. The experience of 'inside' verses 'outside' the chassis envelope a prime example, something I encountered some years ago, but never fully understood. Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric -----Original Message----- From: Bill Owsley [mailto:000000f5a03f18eb-dmarc-requ...@ieee.org] Sent: Saturday, June 24, 2017 8:33 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] USB dongle connector shield filtered grounding Ancient EMC mythology, well proven to be wrong and so abandoned decades ago. And still it pops on occasion and often with new twists to revive the mythology.So it gets ignored as those new to the stories, such that they cannot figure it out, will need the lessons of 'on the job training'. ps. the proper terminology needed to clearly enunciate the concepts is not settled. The physics is plain and simple but to describe it takes a lot words due to a lack of commonly understood terminology. For example 'ground' serves as the catchall term, for shielding, signal return, power return, zero reference, analog return, digital return, chassis, circuit, logic, cable, AND for Safety as in earth ground. Now Maxwell's law's (made up by a mad Scotman back in the 1800's) dictate that a so-called signal must be accompanied by its return signal, and further more that return signal will couple as close as possible to the original so-called signal. The two parts are inextricably intertwined and cannot be considered separately, without great risk to ones grasp of reality. Just as the alleged E-field and H-field are two aspects of the same thing, which conveniently might be called the Poynting Vector, and are related by the Impedance, the ratio of the two fields, which in free space, well away from any conducting structures, is approximately 377 ohms. Now conducting structures, ones like a circuit 'ground', a chassis 'ground', a shielding 'ground' and signal returns often called 'ground' and the concept of 'inside' verses 'outside' which seems to ignore Maxwell, are all going to make for a rich realm of mythology which is not well defined and so, all sorts of imaginings are created to fill all the constructed voids from using all these artificial concepts, when one simple concept is necessary and sufficient to complete the structure. Aside: If that secret, the simple one, was to be 'leaked' to common knowledge, we all would be out of a job in managing EMC since even the simple digital guys could understand it. So we keep it under-wraps and obscure by using mysterious language so that the neophytes and uninitiated think that they understand and/or have no clue as to what is going on. Always the correct answer: "It depends!"- Bill ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
