David:
Perhaps I'm missing something, but all of your 3 methods should yield a correction factor of greater than 20 dB (that is, the 20 dB attenuator plus the LISN coupling loss). Certainly the LISN does not exhibit negative loss. Assuming that you are using a computer data acquisition system, I would prefer to see a correction factor file for each item in the signal train (LISN & attenuator & coax cable), so some typical values at 10 kHz might be something like 4.4 dB plus 19.9 dB plus 0.2 dB. The first option should be the same as the third option, because I would hope that a manufacturer of MIL LISN's would be testing them as the standard requires. Option 2 is just plain not the right way. The third option is the correct concept, and the only correct way is to really measure it. And measure it for every LISN you use, and on a periodic schedule too. Perhaps I was lucky, as my LISN's (of similar models) tracked each other better than a half dB. Also, an LISN can be damaged (electrically more likely than mechanically), so a periodic calibration schedule is required (461F asks for it annually). Finally, remember that the paragraph 5.5.3.4.a that you cited is not a procedure for derivation of the LISN port loss, but rather a check on the whole acquisition system performance, to the rather easy requirement of +/- 3 dB. Ed Price El Cajon, CA USA From: itl-emc user group [mailto:[email protected]] Sent: Wednesday, April 11, 2012 12:17 AM To: [email protected] Subject: [PSES] FW: inquiry concerning MIL STD 461E, CE102 test. Hello I would appreciate any opinions concerning the following MIL STD 461E/F , CE102 test inquiry: Military EMC labs in Israel or out of Israel have different interpretations of the required LISN correction factor to be used ( of main concern is 10kHz - 200kHz, freq. range ) for calculating the final result. Option 1: 20dB + Insertion loss data as supplied by the manufacturer. Option 2: 20dB + measured insertion loss in a 50 OHM system ( as in MIL STD 220 for filter insertion loss ). Option 3: 20dB + LISN, 0.25 Microfarad coupling capacitor loss, as described in section 5.5.3.4 (a).3 and appendix A-56 section 50.5 of MIL STD 461E. The difference between option 1,2 compared to 3 is up to 14dB at 10KHz ( 18dB versus 4.5dB ). Our opinion is that option 3 should be used as it reflects the STD instructions and the real measured level ( at 10kHz the signal gen. is loaded by about 5-6 OHM and not 50 OHM , therefore only the measurement of the LISN input level with the scope represents the real level ). Thanks in advance for any opinions. Regards, David Shidlowsky | Technical Writer Address 1 Bat-Sheva St. POB 87, LOD 71100 Israel Tel 972-8-9186113 Fax 972-8-9153101 Mail [email protected]/[email protected] Web www.itl.co.il <http://www.itl.co.il/> - ---------------------------------------------------------------- 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]> - ---------------------------------------------------------------- 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]>
