RE: EMC EH close field probes / Mindcruiser
Agreeing with both, I wish to add that while the probes are very useful in locating the source and are not (very) useful in predicting the absolute level of far-field emission they may be also useful to predict relative far-field difference in emission, because with all other things equal the far field level will be proportional to the near-field level. Thus it is possible to correlate change in near field with the change in far field. Neven I fully agree with Ken. I have many times used house-made sniffer probes to locate sources (and also coupling paths and/or antennas) of radiated emissions. They helped me identify and fix a number of compliance issues by pointing to the critical elements. That is the real plus of these tools. On the other end, there is no point trying to correlate near and far-field readings. Regards, Paolo -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Friday, November 22, 2002 12:24 AM To: Jim Bacher; Emc-Pstc (E-mail) Cc: 'tkrze...@genius.org.br' Subject: Re: EMC EH close field probes / Mindcruiser My opinion only, curious to see what others say. The relationship between what is measured very close to a source and what is measured at three or ten meters depends very strongly on the efficiency of the radiating element. For example, if a chip by itself were radiating intensely close-in, you would get a very different 3 or 10 m signal than if the chip were connected to a long path on a PCB, and it would radiate still more if that path had a discontinuity in the ground plane beneath it (assuming a high enough frequency) and ground bounce then drove an externally connected cable. So my opinion, for what it's worth, is that trying to correlate measured amplitudes close-in with 3 or 10 m signals is not practical in the general case of troubleshooting a test item. The probe is useful for locating the source of an emission. -- From: Jim Bacher jim.bac...@paxar.com To: Emc-Pstc (E-mail) emc-p...@majordomo.ieee.org Cc: 'tkrze...@genius.org.br' tkrze...@genius.org.br Subject: FW: EMC EH close field probes / Mindcruiser Date: Thu, Nov 21, 2002, 3:46 PM Forwarding for Thomas Krzesaj, please copy Thomas when you respond. -- EMC EH close field probes Message ID: 538546 Hi, I would like to get more informations about close field probes and the measurement methods. What close field value can we consider as critical ? How to interpret the result from the probe ? We actually bought Agilent 11941A 11940a probes and FischerCC EH close field probes. My idea is to get an EMC-scanner like the DetectusAB one (http://www.detectus.se/) to get more repeatibility. Can I get some advices? Thanks, Thomas Krzesaj Genius Instituto de Tecnología Av. Açaí, 875 Bloco E 69075-904 Distrito Industrial Manaus - Amazonas Brasil Tel: +55 92 614-6578 / Fax: +55 92 613-3144 mailto:tkrze...@genius.org.br http://www.thomask.fr.st http://www.genius.org.br Posted on Nov 20,2002 at 07:15am --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send
RE: EMC EH close field probes / Mindcruiser
I fully agree with Ken. I have many times used house-made sniffer probes to locate sources (and also coupling paths and/or antennas) of radiated emissions. They helped me identify and fix a number of compliance issues by pointing to the critical elements. That is the real plus of these tools. On the other end, there is no point trying to correlate near and far-field readings. Regards, Paolo -Original Message- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Friday, November 22, 2002 12:24 AM To: Jim Bacher; Emc-Pstc (E-mail) Cc: 'tkrze...@genius.org.br' Subject: Re: EMC EH close field probes / Mindcruiser My opinion only, curious to see what others say. The relationship between what is measured very close to a source and what is measured at three or ten meters depends very strongly on the efficiency of the radiating element. For example, if a chip by itself were radiating intensely close-in, you would get a very different 3 or 10 m signal than if the chip were connected to a long path on a PCB, and it would radiate still more if that path had a discontinuity in the ground plane beneath it (assuming a high enough frequency) and ground bounce then drove an externally connected cable. So my opinion, for what it's worth, is that trying to correlate measured amplitudes close-in with 3 or 10 m signals is not practical in the general case of troubleshooting a test item. The probe is useful for locating the source of an emission. -- From: Jim Bacher jim.bac...@paxar.com To: Emc-Pstc (E-mail) emc-p...@majordomo.ieee.org Cc: 'tkrze...@genius.org.br' tkrze...@genius.org.br Subject: FW: EMC EH close field probes / Mindcruiser Date: Thu, Nov 21, 2002, 3:46 PM Forwarding for Thomas Krzesaj, please copy Thomas when you respond. -- EMC EH close field probes Message ID: 538546 Hi, I would like to get more informations about close field probes and the measurement methods. What close field value can we consider as critical ? How to interpret the result from the probe ? We actually bought Agilent 11941A 11940a probes and FischerCC EH close field probes. My idea is to get an EMC-scanner like the DetectusAB one (http://www.detectus.se/) to get more repeatibility. Can I get some advices? Thanks, Thomas Krzesaj Genius Instituto de Tecnología Av. Açaí, 875 Bloco E 69075-904 Distrito Industrial Manaus - Amazonas Brasil Tel: +55 92 614-6578 / Fax: +55 92 613-3144 mailto:tkrze...@genius.org.br http://www.thomask.fr.st http://www.genius.org.br Posted on Nov 20,2002 at 07:15am --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: EMC EH close field probes / Mindcruiser
My opinion only, curious to see what others say. The relationship between what is measured very close to a source and what is measured at three or ten meters depends very strongly on the efficiency of the radiating element. For example, if a chip by itself were radiating intensely close-in, you would get a very different 3 or 10 m signal than if the chip were connected to a long path on a PCB, and it would radiate still more if that path had a discontinuity in the ground plane beneath it (assuming a high enough frequency) and ground bounce then drove an externally connected cable. So my opinion, for what it's worth, is that trying to correlate measured amplitudes close-in with 3 or 10 m signals is not practical in the general case of troubleshooting a test item. The probe is useful for locating the source of an emission. -- From: Jim Bacher jim.bac...@paxar.com To: Emc-Pstc (E-mail) emc-p...@majordomo.ieee.org Cc: 'tkrze...@genius.org.br' tkrze...@genius.org.br Subject: FW: EMC EH close field probes / Mindcruiser Date: Thu, Nov 21, 2002, 3:46 PM Forwarding for Thomas Krzesaj, please copy Thomas when you respond. -- EMC EH close field probes Message ID: 538546 Hi, I would like to get more informations about close field probes and the measurement methods. What close field value can we consider as critical ? How to interpret the result from the probe ? We actually bought Agilent 11941A 11940a probes and FischerCC EH close field probes. My idea is to get an EMC-scanner like the DetectusAB one (http://www.detectus.se/) to get more repeatibility. Can I get some advices? Thanks, Thomas Krzesaj Genius Instituto de Tecnología Av. Açaí, 875 Bloco E 69075-904 Distrito Industrial Manaus - Amazonas Brasil Tel: +55 92 614-6578 / Fax: +55 92 613-3144 mailto:tkrze...@genius.org.br http://www.thomask.fr.st http://www.genius.org.br Posted on Nov 20,2002 at 07:15am --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
