David, That is not something I have really thought much about. However, we do use a clamp with an EM shield (as most clamps have) and have a short braided ground strap from the clamp to the ground plane. I would hope this would reduce some of the effect you mention. We have noticed that the clamp has affected the pass/fail results of an EUT with high impedance, but only if the EUT was passing/failing with very little margin to begin with. As I recall, the influence of the clamp in the circuit was less than 1 dB, and since we generally overtest with a 3dB margin, we have not considered this to be a significant problem. Bob Richards, NCT.
"Sterner, David (S&FS)" <[email protected]> wrote: Inserting a current clamp between the E-M clamp and EUT could give misleading data. The radiated field is high near the EUT side of the E-M clamp (check it with a field probe) due to impedance mismatch. Not only does the clamp couple into the field, but it also disturbs the field, introducing measurement error. _ Honeywell David W. Sterner Quality Assurance Engineering Security & Custom Electronics 2 Corporate Center Drive Melville, NY 11747 Phone: (516) 577-2321 Fax: (516) 577-3540 [email protected] [email protected] Electromagnetic Compatibility IEEE 05888136 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
