Re: Multiple shield terminations?
Some years ago, I had to show a TV-card vendor (their card made a compliant computer fail Class B) the right way to do this. They were passing normal video through, and had apparently never TESTED in standby mode to see what interrupting shields with pigtails would do. I bundled all the video cable shields - in their case only six - and terminated the whole bunch in common at the connector EMI backshell. That did it. As I recall, they wouldn't DO that, and we didn't buy their card. Good luck. Cortland --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
RE: Multiple shield terminations?
Derek, Suggest using a connector having #(Conductors + Braids), pins. Bond all the Braid pins together and ground, (Or continue thru the connector as desired), via shortest connection. For symmetry, Braid Pin Ground Ring could be made around outside periphery of connector pins. Good Luck! Tony Firth, EE, Genus,Inc.,Sunnyvale,CA -- Hi Ken, I'm open to this, but the cables that pass through ( there could be as many as 10 ), all have their own braids, and are impedance matched. I really don't want to just squish them together and hope it makes good contact all around Not sure if I'd change the cables impedance ( they are impedance controlled cables ) at the clamping point Cheers, Derek N. Walton
MIL-HDBK-454 (Safety)
Over the years a number of US MIL standards have been replaced by MIL guidance handbooks (for instance MIL-STD-454 has been replaced by MIL-HDBK-454). The MIL standards were full of "shalls" whereas the MIL-handbooks are full of "shoulds". This shift is rather unfortunate from a contractual point of view since MIL handbook 454, for instance, states that it cannot be used to place mandatory requirements and the designer need not comply with the guidance provided. This seems to be particularly unfortunate since MIL-STD-454 (Requirement 1) was probably the most important souce of MIL personnel safety requirements. The specifications for numerous US military items, however, still refer to this guidance handbook as if it is a repository of mandatory requirements. In reality this seems to me to leave the issue of what the equipment design actually complies with as completely undefined. I would like to hear any opinions as to how MIL-HDBK 454 is perceived from a contractual standpoint. How much freedom do US military equipment designers out there feel they actually have, given the complete lack of "shalls"? Dave Palmer, UK
Re: Multiple shield terminations?
Is this mil or commercial? Are they twisted shielded, or coax? There are of course MIL-C-38999 connectors with coaxial pins. If it is twisted shielded I doubt that a short length of shield termination would cause huge vswr to the intentional differential signal. Especially as a two inch termination is a tenth wavelength at 600 MHz. Likely I don't know enough about your problem. -- From: lfresea...@aol.com To: ken.ja...@emccompliance.com, emc-p...@majordomo.ieee.org Subject: Re: Multiple shield terminations? List-Post: emc-pstc@listserv.ieee.org Date: Sat, Jul 13, 2002, 11:10 AM Hi Ken, I'm open to this, but the cables that pass through ( there could be as many as 10 ), all have their own braids, and are impedance matched. I really don't want to just squish them together and hope it makes good contact all around Not sure if I'd change the cables impedance ( they are impedance controlled cables ) at the clamping point Cheers, Derek N. Walton Owner, L. F. Research EMC Design and Test Facility 12790 Route 76, Poplar Grove, IL 61065 www.lfresearch.com
Re: Multiple shield terminations?
Hi Ken, I'm open to this, but the cables that pass through ( there could be as many as 10 ), all have their own braids, and are impedance matched. I really don't want to just squish them together and hope it makes good contact all around Not sure if I'd change the cables impedance ( they are impedance controlled cables ) at the clamping point Cheers, Derek N. Walton Owner, L. F. Research EMC Design and Test Facility 12790 Route 76, Poplar Grove, IL 61065 www.lfresearch.com
Re: Multiple shield terminations?
What's wrong with the simple-minded approach - an EMI backshell? -- From: lfresea...@aol.com To: emc-p...@majordomo.ieee.org Subject: Multiple shield terminations? List-Post: emc-pstc@listserv.ieee.org Date: Sat, Jul 13, 2002, 3:03 AM Hi all, I'm faced with a situation where a number ( up to 10 ) of small ( 3mm ) shielded wire pais come together at a connector. I need to provide a peripheral termination for each shield. Has anyone come across and off the shelf solution for this? Alternatively, a good way of achieving this? Thanks, Derek N. Walton Owner, L. F. Research EMC Design and Test Facility 12790 Route 76, Poplar Grove, IL 61065 www.lfresearch.com
Multiple shield terminations?
Hi all, I'm faced with a situation where a number ( up to 10 ) of small ( 3mm ) shielded wire pais come together at a connector. I need to provide a peripheral termination for each shield. Has anyone come across and off the shelf solution for this? Alternatively, a good way of achieving this? Thanks, Derek N. Walton Owner, L. F. Research EMC Design and Test Facility 12790 Route 76, Poplar Grove, IL 61065 www.lfresearch.com
