Rich:
It’s easier to prove the functional performance of shielded enclosure filters using the technique I described. Of course, a polite test lab would also not want their immunity testing to spill out into the environment. When you are exposing some gadget to 200 Volts per meter, you certainly don’t want to crash the company payroll computer or cause nearby NC machines to dance their cutters into their work-pieces. At my lab, I have the further incentive by being at the perimeter of an airport and directly under the glide-path. Although I have never quantitatively measured the filter attenuation of my enclosure powerline filters in an “outgoing” direction, I have done some spot checks. At several “quiet” frequencies across the range I typically use, I have placed an antenna outside my chamber while generating high-level immunity fields inside the chamber. The result was that I was never able to see any leaking immunity signal that was discernable from the external noise. Since that time, I have relied on another subjective criteria. Projects that come to my lab for immunity testing typically arrive with a large collection of non-deliverable electronic support equipment. The key thought here is “non-deliverable”, a term meaning that this stuff is a collection of whatever junk and debris the program engineers found in a back storage shed. Atrocious power supplies, unshielded pre-amps, interfaces wired on open perf boards and cabling of dubious shielding ability. Add to this a few commercial laptop computers and their owners with cell phones in their pockets. If I can generate my immunity levels inside the chamber without affecting the operation of this set of “wideband detectors” (located immediately outside my chamber), I feel fairly confident that I’m not degrading the external electromagnetic environment beyond the perimeter of my lab. Ed Price [email protected] <blocked::mailto:[email protected]> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty From: [email protected] [mailto:[email protected]] On Behalf Of Jones, Richard (Richard) Sent: Friday, September 10, 2010 1:12 PM To: [email protected] Subject: RE: [PSES] Power Line Filters for EMC Chambers This is interesting, I had interpreted it to mean that I was checking to ensure no RF was getting out of the chamber rather than getting in. I guess it’s fairly safe to say if I don’t measure anything inside probably nothing is getting out either! The question actually came out of ISO 17025 where it states: 150-11 5.5.1 b) Requirements for checking associated critical equipment, such as power line filters, and grounding systems shall also be specified and the results documented. I was thinking along the lines of 100dB performance and taking actual measurements, which after looking at Mil Std 220 and CISPR17 isn’t for the faint hearted! Rich From: Price, Edward [mailto:[email protected]] Sent: Friday, September 10, 2010 3:35 PM To: [email protected] Subject: Re: [PSES] Power Line Filters for EMC Chambers Rich: If you mean testing the RF filtering performance of the filters, you could just use a very empirical approach. After all, what are the filters supposed to do? Answer, keep RF noise out of the chamber. If you periodically do a conducted and radiated emission ambient check inside the chamber, and, if you don’t detect any emissions, then the filters are working. Ed Price [email protected] <blocked::mailto:[email protected]> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty From: [email protected] [mailto:[email protected]] On Behalf Of Jones, Richard (Richard) Sent: Friday, September 10, 2010 9:35 AM To: [email protected] Subject: RE: [PSES] Power Line Filters for EMC Chanmbers For EMC labs: Does anyone have a method for testing Power Line Filter performance once installed on an EMC Chamber. I was asked this question recently as our filters are over 10yrs old, at the time I couldn’t think of anything short of removing them to test performance. I did wonder if some simple verification of filter current leakage to ground would suffice as capacitors age but the inductors less so, ofcourse that’s not checking actual performance. The installation is visually checked and grounding measured regularly and up until now no other thought was given to it. Rich - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
