Re: [PSES] FCC EMI Test and Ferrites on Cables - a conundrum

[Doug Powell]

Pat, It is incumbent on the original manufacturer to include any information pertinent to the correct use and operation of the product. ‎Many manufacturers have a "Conditions of Use" section in in their user manuals right behind the safety section. Of course would include any required I/O cables.   As for supplying the correct cable, many products in the past had non-detachable cords with a molded in ferrite, nowadays with so much modularity, this is not always the case. HDMI cables being one example.   ‎If it were my product, I would have a few options. Ship one cable of the correct type with each product, make the same cable available as an accessory or replacement part and finally add a disclaimer stating other similar cables will not perform to the same level of expectation and will exceed emissions limits.  In other words, use only the cable provided by the company. By so doing, the liability of misuse of the product stays with the end user.  If you start down the path of describing a certain brand of cable (not your own), a certain type of ferrite (not available to most end users) and a certain positioning of the ferrite on the cable, you are now advising the end user on their own application and thereby assuming liability for any interference.   It is best to keep it simple and to the point.  Make available a complete setup that actually works. If the end user chooses to go another route, it is on their own head.   Thanks, - doug Douglas Powell http://www.linkedin.com/in/dougp01   From: Pat Lawler Sent: Sunday, September 7, 2014 7:59 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Reply To: Pat Lawler Subject: Re: [PSES] FCC EMI Test and Ferrites on Cables - a conundrum All, I was looking through sales ads for electronics equipment, and saw a Blu-Ray disc player from a major company that came with an HDMI cable. In the past, I would have just considered this a convenience to the buyer, like including batteries for remote controls.  Now, I'm wondering if the HDMI cable had ferrites, or came from a qualified vendor list of known-good cable manufacturers. If a company has to supply a cable to control emissions, does that fact need to be reinforced in the user's manual?  For example, 'Use only supplied HDMI cable or equivalent', or 'Use only <company> brand products for best performance.' Pat Lawler plawl...@gmail.com On Thu, Sep 4, 2014 at 9:31 AM, Gary McInturff <gary.mcintu...@esterline.com> wrote: Playing the devil advocate here only because I find this interesting and I'm not advocating anything. Heck I'm probably just arguing for argument sake.  If all cables are not equal as Ghery and note and the designer/manufacturer has knowledge of that don't the cables then become special accessories in their own right? Under 15.27 c) They would not normally be considered special accessory items  under the definition because they can be easily purchased at a multitude of locations.         15.27 c) Accessory items that can be readily obtained from multiple retail outlets are NOT (my emphasis)  considered to be special accessories ... But given the knowledge of the designer/manufacturer that cables vary in performance and not all cables were tested the only assurance they have that the system will perform as intended is buy telling the consumer exactly which cable they must use buy name and brand. But if they do that then the cable isn't "readily obtained from multiple outlets" and is now by definition a special accessory. Paragraph 15.27 says that "The party responsible for the equipment, as detailed in §2.909 of this chapter, shall ensure that these special accessories are provided with the equipment" So now must the cable be provided? Gmac -----Original Message----- From: Pettit, Ghery [mailto:ghery.pet...@intel.com] Sent: Thursday, September 04, 2014 12:46 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] FCC EMI Test and Ferrites on Cables You are highly unlikely to find the ferrite prayer beads at Best Buy.  If you don't specify which ones to get you have no idea what the result will be.  I think you are correct, the beads must be shipped with the product.  The right ones, to boot. Now, how does the designer know that he needs ferrite beads?  My experience has been that many (most?) HDMI cables do not have their shields terminated properly, if at all.  Once the shields are terminated correctly problems go away.  Could this be a better solution? Ghery S. Pettit - ---------------------------------------------------------------- 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher:  <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>