Derek: I think the comments about using batteries were aimed at the fact that a battery has very low impedance, and can serve as a big "capacitor", smoothing out the noise from a noisy supply. Also, with the battery supplying some of the load, the supply is not working as hard, so maybe it would be contributing less noise too.
You mentioned that LISN and facility powerline filter impedances were too high to allow starting of your EUT. You could temporarily jumper around the LISN path, or even the facility filter path, in order to start the EUT, and then remove the jumpers during testing. Finally, you could look around (eBay?) for some old brute force linear supplies, like the old Sorenson that I use. A couple of these in parallel could get you a much quieter source. Even a single linear in parallel with your noisy switcher could allow the switcher to contribute less noise. Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf > Of Derek Walton > Sent: Friday, August 21, 2009 10:00 AM > To: Ken Javor > Cc: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: 28 volt Linear Power Supply > > Hi Everyone, > > thanks for the constructive comments so far. > > I'm not really in a position to use batteries, my voltage > spec is very tight at +- 0.5 volts. > > I have tried running through the facility filters, they are > 100 amp rated, but I think a combination of that impedance > and the LISN impedance is too much for the EUT starting > current. It seems I can start the EUT with just the LISN's, > but then I have too much noise from my power source. > > I swapped the room filters for some 10 uF caps, same ones > that are called out in MIL std testing, and I almost get quiet enough. > > Ideally, I'd like to find a quieter source rather than try to > filter..... > > Sincerely, > > Derek Walton - 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>
