Ken:
Why did the committee settle on the value of 20 dB for the CE102 attenuator? I know that transient current changes in the LISN load can cause energy to be coupled into the analyzer, possibly damaging the analyzer input, so some protection is a good idea. And, if you do have a high signal level, it's better practice to reduce it externally rather than risk the attenuators within your analyzer. OTOH, I hate to see a "flat line" instead of the real analyzer noise floor plus very low-level signals, when measuring really quiet test specimens. I realize that contemporary analyzers have a noise floor way, way below the limit value, but that's not a good reason to give away 20 dB of sensitivity. I realize that there is also a question of impedance matching of the analyzer input to the 50-Ohm feed system. True, that used to be a problem with the equipment we now have on our collection shelves (like an NF-105 or NM-50), but is impedance error still a real issue with contemporary analyzers? MIL testing is not just a "pass / fail" concept; you are also gathering data that other engineers may need to evaluate for future system integration (possibly at limits more stringent than your current testing). So, why is 20 dB specified; why not 10 dB or 6 dB or 3 dB or even 0 dB? Could the standard allow attenuation to be optional? If some attenuation is felt to be necessary, could a 3 dB attenuator be specified as the minimum, with possibly larger values "recommended"? Ed Price El Cajon, CA USA From: Ken Javor [mailto:[email protected]] Sent: Wednesday, April 11, 2012 6:58 AM To: [email protected] Subject: Re: [PSES] FW: inquiry concerning MIL STD 461E, CE102 test. As a member of the committee that writes MIL-STD-461, I second Ed's advice: option 3 is the only correct technique. Ken Javor Phone: (256) 650-5261 - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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]>
