If I understand the message below, it¹s not that fuzzy. One can predict electric field intensity in the far field as a function of cable cm current. So there is a number to work with from the get-go. Of course the final check has to be an RE test, but if the cm current meets the computed cm limit, than the RE from that cable should meet the RE limit.
Ken Javor Phone: (256) 650-5261 From: Bill Owsley <000000f5a03f18eb-dmarc-requ...@ieee.org> Reply-To: Bill Owsley <wdows...@yahoo.com> Date: Thu, 14 Jan 2016 07:21:02 +0000 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Current probe for CM currents Ok, so call me lazy, real lazy ! clamp on your probe, measure a number, and then work to reduce that number by twice what is needed to meet the limit, then re-test. Repeat, if necessary. The really big trick in this process is knowing how to reduce the measured number of the problem that has shown up. Sucks to be you. ps. I have used that same technique for years. It works really well when done with relative measurements. pps. a couple of products needed more than halving the number measured at the beginning. ppps. correct fixes usually kill the problem, not just reduce it. But there are exceptions. > > > > > > From: Ken Javor <ken.ja...@emccompliance.com> > To: EMC-PSTC@LISTSERV.IEEE.ORG > Sent: Wednesday, January 13, 2016 4:25 PM > Subject: Re: [PSES] Current probe for CM currents > > > > Re: [PSES] Current probe for CM currents > I re-read the query and see I didn¹t address the actual question. The current > probe inserts an impedance given by the transfer impedance divided by the > winding turns ratio. Once you have measured the transfer impedance and > computed the inserted impedance, you can then judge the inserted impedance > against the cable impedance itself to assess any perturbation of the quantity > to be measured. > > Ken Javor > Phone: (256) 650-5261 > > > > From: Ken Javor <ken.ja...@emccompliance.com> > Date: Wed, 13 Jan 2016 15:15:55 -0600 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Conversation: [PSES] Current probe for CM currents > Subject: Re: [PSES] Current probe for CM currents > > A current probe measures the net current on the conductor within its opening. > The impedance of the circuits attached to that conductor may affect how much > current flows through the conductor, but not the measurement thereof. > > Ken Javor > Phone: (256) 650-5261 > > > > From: Amund Westin <am...@westin-emission.no> > Reply-To: Amund Westin <am...@westin-emission.no> > Date: Wed, 13 Jan 2016 18:48:23 +0100 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: [PSES] Current probe for CM currents > > Planning to do some EMI troubleshooting with a «homemade» current probe. > Probing a lot of cables inside a rack and try to find the source. > Will make a current probe by a ferrite core (two halves, a few turns wire and > coax plug) as many EMI experts have posted on the web and on this forum. > Then find the Zt[dBohm], so make a measurement on a cable and verify the > readings on the spectrum. > > But when clamping on the current probe, which is a ferrite, does that change > the cable impedance and therefore actually changes the real current flow, so > my reading will not be true? ... or am I missing some fundamental theory here? > ... > > #Amund > > > - > ---------------------------------------------------------------- > > 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 > <emc-p...@ieee.org> > > 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 <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > > - > ---------------------------------------------------------------- > 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 > <emc-p...@ieee.org> > 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 <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > > > > > - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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 <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
