Hi Brent and the group, An earlier article I wrote (using a less realistic setup) poses an explanation. The URL is: http://emcesd.com/tt010100.htm
When fed from the EUT end of the clamp, the EUT sees first the pulse which then goes down the one meter clamp (a 50 Ohm line) and reflects off the (almost) open end (minus the energy heading for the AUX) and comes back about 10 ns later. This gives the double hump in the article above. (2 meter round trip, ~6 feet at ~1.5 ns/foot, gives about 10 ns delay) At the AUX end, the incident and reflected pulses are coincident and line up giving a higher pulse in that direction. Doug Brent DeWitt wrote: > Very interesting data Doug! Now the interesting question is why? Looking > at the delays and waveform shapes, it seems possible that the pulse > reflecting from the far end of the clamp (open ended transmission line) may > be destructively adding to the pulse toward the EUT. > > Other thoughts anyone??? > > Brent DeWitt > > > >>-----Original Message----- >>From: [email protected] [mailto:[email protected]]On >>Behalf Of Doug Smith >>Sent: Thursday, June 02, 2005 3:53 PM >>To: emc-pstc >>Subject: IEC 61000-4-4 analysis >> >> >>I have been hanging out in the lab and doing more experiments, this >>time on the 61000-4-4 Capacitive Clamp. The clamp is quite directional >>and this can cause test problems including failing compliant systems. >> >>Abstract: Analysis is performed of the currents injected by the IEC >>61000-4-4 Capacitive Clamp using current probes. Surprising results of >>the current measurements indicate that the Capacitive Clamp is >>directional and sends more energy to the support equipment (AUX) than >>to the equipment under test (EUT)! The directional property of the >>Capacitive Clamp also leads to a common lab error where significantly >>more energy is applied to the EUT if the clamp is not properly >>connected, potentially causing compliant equipment to fail the test. >>(Almost every EMC test lab I know has made this error!) >> >>The link to the article is the picture of the experimental test setup >>at the bottom of the home page at http://emcesd.com . >> >>Doug >>-- >>------------------------------------------------------- >> ___ _ Doug Smith >> \ / ) P.O. Box 1457 >> ========= Los Gatos, CA 95031-1457 >> _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 >> / /\ \ ] / /\ \ Mobile: 408-858-4528 >>| q-----( ) | o | Email: [email protected] >> \ _ / ] \ _ / Website: http://www.dsmith.org >>------------------------------------------------------- >> >>---------------------------------------------------------------- >>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/listserv/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: >> >> Richard Nute: [email protected] >> Jim Bacher: [email protected] >> >>All emc-pstc postings are archived and searchable on the web at: >> >> http://www.ieeecommunities.org/emc-pstc >>-- >>No virus found in this incoming message. >>Checked by AVG Anti-Virus. >>Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005 >> > > -- > No virus found in this outgoing message. > Checked by AVG Anti-Virus. > Version: 7.0.322 / Virus Database: 267.4.1 - Release Date: 6/2/2005 > > > -- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org 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/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
