Correction: My response went to the definition of voltage distortion on a dc bus. I am not familiar with any particular test method for measuring the distortion due to a load. I would think that if you are controlling distortion from a particular you would have to measure current distortion >from a stiff source, not the voltage distortion I described. And I also think you would have to be very careful to discriminate between audio frequency effects and the distortion due to a dc/dc converter - the latter should not be considered a voltage distortion controlled by MIL-STD-704, it is an rf effect. That's why in my original response I said that a voltage distortion spec and measurement should be low-pass limited.
> From: "Brian O'Connell" <[email protected]> > Date: Wed, 25 Apr 2007 08:27:30 -0700 > To: "'IEEE EMC Discussion Group'" <[email protected]> > Subject: RE: MIL HBK 704-8 distortion factor > > "Distortion" for a 28Vdc bus, in accordance with MH-704-8, is defined in > that standard and in MH-704-1 (for performance level). The diagrams in > MH-704-8 clearly indicate test requirements/conditions. Do not use > additional equipment or deviate from these requirements. This is a simple > test (but long), so do not make it complicated. Performance requirements > are dependendent on the UUT specs. > > The tester should understand that these test conditions are not contrived, > and are based on empirical measurements from various aircraft and ground > vehicle 28V bus. > > In a previous life, I used programmable sources from Chroma, Xantrex, and > Elgar for this test. Some of these sources can provide direct modulation, > so the transformer-coupled generator would not be required. > > luck, > Brian > > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of Ken Javor > Sent: Wednesday, April 25, 2007 7:14 AM > To: IEEE EMC Discussion Group > Subject: Re: MIL HBK 704-8 distortion factor > > Isn't the distortion factor on a dc line just the rms equivalent of the > total ripple divided by the dc potential, in this case 20 Volts? I would > use a true rms voltmeter with the proper bandwidth to measure the ripple. > Or one of the older audio frequency EMI receivers that could scan from 30 > Hz to 20 or 50 kHz, but could also look at the whole audio band > simultaneously, such as the Stoddart/Singer/Eaton Ailtech NM-10, the > Electro-Metrics EMC-10, or the Empire Devices/Singer NF-315. If today the > "proper bandwidth" is taken to be something like 500 kHz (with which I > disagree, but then no one asked me, either) then you might need to use > something like a Krohn-Hite active filter set to low pass at 500 kHz, into > an oscilloscope with some kind of true rms capability. > > > From: "Derek Walton" <[email protected]> > Organization: L F Research > Reply-To: [email protected] > Date: Wed, 25 Apr 2007 08:52:09 -0500 > To: "IEEE EMC Discussion Group" <[email protected]> > Subject: MIL HBK 704-8 distortion factor > > Good day all, > > I'm trying to determine how to measure the distortion factor required by > method LDC104 in MIL HBK 704-8. > > The requirement is to measure the distortion factor on a 28 volt dc power > line. Can anyone point me in the best way to do this? > > Thanks, > -- > Derek N. Walton > Owner L F Research > www.lfresearch.com <http://www.lfresearch.com> > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > 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] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
