Hi All, A few years ago, I started to generate some data for a tutorial on shielded magnetic field loops for new engineers. As happens most of the time with my research on most topics, I found out most of what I and everyone thought about shielded magnetic field loops was wrong. The electric field shielding only works for a special case in the far field where the E-field is symmetric around the centerline of the probe. Even then, the shielding does not work in the near field. Here are three of my articles and a paper on the subject:
* June 2008, The Square Shielded Loop - Part 2, Parasitic Coupling<http://emcesd.com/tt2008/tt060208.htm> (Electric Field Shielding of Magnetic Loops is Not Always Effective!) * July 2008, The Square Shielded Loop - Part 3, Parasitic Coupling Between Unshielded Wire Loops<http://emcesd.com/tt2008/tt070508.htm> * August 2008, The Square Shielded Loop - Part 4, Coupling to a PCB<http://emcesd.com/tt2008/tt080108.htm> (From Shielded and Unshielded Magnetic Loops) * Signal and Noise Measurement Techniques Using Magnetic Field Probes<http://emcesd.com/pdf/emc99-w.pdf> (~600K) * (1999 IEEE EMC Symposium paper) In the near field, the shield generates a parasitic resonance that is not good. Unshielded loops do not have this problem. It is instantaneous to check for any problems E-fields may cause with unshielded loops, and know the amount of the effect if there is any. Paperclip loop 1 Shielded loop 0 I love to cover topics like this in my classes and on my website that run counter to common knowledge. It is a lot of fun for me. I don't think of myself as an expert on anything but a student of everything (things like all aspects of engineering, thermodynamics [that is how at 72 I can run miles in the summer desert heat while everyone else is dying of the heat], engine lubrication, medicine, etc.). Doug [SYMBOL] - ---------------------------------------------------------------- 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]>
