One cannot use the transfer impedance of a current probe to convert a current into a potential to be compared to a dBuV limit, because the potential then depends on which current probe is in use, irrespective of how much current flows, and into what impedance.
Either a limit based on current is verified using a current probe, in which case the transfer impedance is immaterial, except to reduce the data, or a LISN with impedance specified over the frequency range of the requirement is employed. Many years ago, MIL-STD-461 used the same LISN as for CISPR measurements, and the LISN was (is) indeed characterized down to 10 kHz. My understanding is that CISPR now use a different LISN, and that would need to be separately characterized. Finally, keep in mind that VDE limits did go down to 9 kHz, and they added a 250 uH ³add-on² LISN to stabilize the impedance of the CISPR LISN at those lower frequencies. Ken Javor Phone: (256) 650-5261 From: "McDiarmid, Ralph" <[email protected]> Reply-To: "[email protected]" <[email protected]> Date: Mon, 16 Sep 2013 13:52:00 -0700 To: <[email protected]> Subject: Re: [PSES] question - emission measurements below 150kHz Dear EMC-PSTC forum members, Given a need to measure conducted emissions from 150kHz down to 9kHz, would it be better to: 1. characterise 50ohm LISN for insertion loss down to 9kHz 2. use a current clamp rated for that frequency and use transfer impedance to determine dB(uV) I can see that impedance of 50ohm/50uH LISN could be an issue at frequencies < 100kHz approx. thanks, ____________________________________________________________________________ ___ Ralph McDiarmid | Schneider Electric | Solar Business | CANADA | Regulatory Compliance Engineering - ---------------------------------------------------------------- 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://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.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://www.ieee-pses.org/list.html (including how to unsubscribe) 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]>
