Hi Brain, ken, I must be missing something here:
I don't find distortion factor defined in either part 1, or part 8. If I google the web, I get a plethora of responses. Nor are theree ANY indication of what parameters are important in the distortion instrument. I like simple... but this is not written in a simple fashion. The test method has a table with amplitudes: are we to assume that we use an arb to generate each frequency with the respective amplitude ( into a resistive load ) and were done? Just fyi, when that's done in Mathmatica, it looks nothing like TRU ripple on an aircraft. Back to the distortion measurement, are we trying to determine how an EUT modifies the ripple spectrum set into a resistive load? If that's the case, the power supply is critical, and there are no controls on it, e.g. BW, source Z, power etc. Why I'm involved in this is I'm a 3rd party lab trying to resolve a problem where 2 labs, with different power supplies ( both supposedly generating the correct ripple ) give differing results on the same EUT. Can you help me see what I'm missing here. Thanks, Derek. Ken Javor wrote on 4/25/2007, 10:59 AM: > 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 > -- Derek N. Walton Owner L F Research www.lfresearch.com Phone: (815) 566 5655 - 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 ______________________________________________________________________
