"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 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] List-Post: [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 email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
