I have the feeling that different issues are mixed in this discussion. supposed that CE vs. RE methods is the issue, I can give you some historical information. The CE method is used as a simplified method for the radiation of the tested device. The CE method was used for devices which have to met several conditions 1. the cable length was long compared to the size of the device ( the longest side should not be longer than 80 cm) 2. the number of cable is limited to one or maximum 2 cables. 3. the frequencies produced in the equipment have to be low due the limitation of the method to 300 MHz.
Reasons for 1. the cable should be the preferred antenna for the emission of the device 2. You can only made a correlation between CE and RE if all the radiated by the one cable. You will not be able to calculate the sum of different cables because you don't know the relation. 3. The method is only specified up to 300 MHz. At higher frequencies the cables act different. This method was used e. g. simple household devices and tools. I don't know if I got the real point because I didn't followed the whole discussion, but perhaps I can put in some more ideas. Best Regards Lothar Schmidt Technical Manager EMC/Bluetooth, BQB, Competent Body Cetecom Inc. 411 Dixon Landing Road Milpitas, CA 95035 Phone: +1 (408) 586 6214 Fax: +1 (408) 586 6299 -----Original Message----- From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Tuesday, January 16, 2001 7:45 AM To: Ralph Cameron; chris maxwell; dan kwok Cc: EMC-PCST (E-mail) Subject: Re: Site Correlation I am getting the distinct (but uncomfortable) feeling that was is being discussed by a lot of people on this thread is that cable cm CE need to be controlled to prevent either crosstalk to another bundle, or to prevent interference to equipment connected to the same bundle. Am I interpreting these comments correctly? For the record, I don't believe either of these is a real issue. The only traditional, and in my experience, legitimate purpose of controlling cable cm CE is to prevent coupling to the antennas connected to radio receivers. Ken Javor ---------- >From: "Ralph Cameron" <ral...@igs.net> >To: "Chris Maxwell" <chris.maxw...@gnnettest.com>, "Ken Javor" <ken.ja...@emccompliance.com>, "dan kwok" <dk...@intetron.com> >Cc: "EMC-PCST \(E-mail\)" <emc-p...@majordomo.ieee.org> >Subject: Re: Site Correlation >Date: Tue, Jan 16, 2001, 9:01 AM > > What it boils down to Chris is the lack of immunity of the consumer > equipment contributes to degradation of the intended function. Once the > undesired energy reaches the consumer device there's no way to get rid of > it. The rememdy is to prevent it from reaching the device and or isolating > it from the source. > > At one time injection clamps were used for immunity testing- are they still? > > Ralph Cameron > > > ----- Original Message ----- > From: "Chris Maxwell" <chris.maxw...@gnnettest.com> > To: "'Ralph Cameron'" <ral...@igs.net>; "Ken Javor" > <ken.ja...@emccompliance.com>; "dan kwok" <dk...@intetron.com> > Cc: "EMC-PCST (E-mail)" <emc-p...@majordomo.ieee.org> > Sent: Tuesday, January 16, 2001 8:38 AM > Subject: RE: Site Correlation > > >> Seems like this thread has gotten into how to correlate common mode cable >> currents with their expected radiated emissions. >> >> For those interested, Fischer Custom Communications makes coupling and >> measuring clamps which can measure common mode surface currents on cables >> and surfaces. They used to publish some application notes regarding the >> usage of their clamps to measure surface/cable currents and how to > correlate >> them to expected radiated emissions. >> >> I read them a couple of years ago. I never bought the clamps, but it did >> make for some very good technical reading. >> >> I do know of a table top power supply manufacturer that uses this method >> almost exclusively. They send one power supply to a calibrated OATS. > They >> get it to pass. Then, when the sample comes back to the factory, they > take >> clamp measurements of the common mode currents of the AC input and DC > output >> cable. >> >> They then model the power supply as a dipole antenna with the AC input > cable >> and DC output cable being the two poles. >> >> For future power supplies, they then use the clamp method in-house to >> measure the cable currents, if the currents pass, they assume the supply >> passes radiated emissions. >> >> This won't work for every product, but it does fit this application well. >> The power supply company could make more than 10 versions (3.3VDC, 5VDC, >> 9VDC, 12VDC ...) of a power supply with the same case and cabling so it > can >> save them a great deal of time and money. The supplies only have two >> cables, which is easy to model. The supplies have clock speeds in the >> 100-500Khz range, meaning that most of thier harmonics will be "dead" over >> 230Mhz, which is the cutoff for most coupling clamps. >> >> I thought that this method would be difficult to use for our products > since >> we have higher clock speeds and multiple cables. >> >> I guess many times the measurement method is somewhat defined by what > you're >> measuring. >> >> Chris Maxwell >> Design Engineer >> GN Nettest >> 6 Rhoads Drive, Building 4 >> Utica,NY 13502 >> email: chris.maxw...@gnnettest.com >> phone: 315-266-5128 >> fax: 315-797-8024 >> >> >> >> >> > -----Original Message----- >> > From: Ralph Cameron [SMTP:ral...@igs.net] >> > Sent: Monday, January 15, 2001 10:57 PM >> > To: Ken Javor; dan kwok >> > Cc: EMC-PCST (E-mail) >> > Subject: Re: Site Correlation >> > >> > >> > No, your message is clear, what I am saying is that the emissions below >> > 30Mhz cause the majority of the interference problems to consumer >> > electronics and that's not being addressed. >> > >> > Ralph Cameron >> > >> > ----- Original Message ----- >> > From: "Ken Javor" <ken.ja...@emccompliance.com> >> > To: "Ralph Cameron" <ral...@igs.net>; "dan kwok" <dk...@intetron.com> >> > Cc: "EMC-PCST (E-mail)" <emc-p...@majordomo.ieee.org> >> > Sent: Monday, January 15, 2001 10:34 PM >> > Subject: Re: Site Correlation >> > >> > >> > > I must have been unclear in my previous message. The purpose of >> > controlling >> > > cable cm CE is to control the resultant cable-induced RE, which are >> > > controlled to protect tunable antenna-connected radio receivers, > period. >> > > There was never any other purpose for controlling CE or RE. >> > > >> > > Ken Javor >> > > >> > > ---------- >> > > >From: "Ralph Cameron" <ral...@igs.net> >> > > >To: "Ken Javor" <ken.ja...@emccompliance.com>, "Dan Kwok" >> > <dk...@intetron.com> >> > > >Cc: "EMC-PCST \(E-mail\)" <emc-p...@majordomo.ieee.org> >> > > >Subject: Re: Site Correlation >> > > >Date: Mon, Jan 15, 2001, 8:51 PM >> > > > >> > > >> > > > Perhaps what you state is correct Ken but there has been a > supposition >> > that >> > > > RE , induced or other wise when converted to conducted current does >> > not >> > > > effect other devices connected to those same conductors whether they >> > be >> > > > power, incoming TV or telephone cables etc. All these conductors >> > intercept >> > > > RE and their effects have been eliminated in 90% of cases( I have >> > > > personally suppressed ) , by suppresseing the common mode > signals.Over >> > 300 >> > > > successes is a significant statistic. >> > > > >> > > > Ralph Cameron >> > > > >> > > > >> > > > . >> > > > ----- Original Message ----- >> > > > From: "Ken Javor" <ken.ja...@emccompliance.com> >> > > > To: "Dan Kwok" <dk...@intetron.com>; "Ralph Cameron" > <ral...@igs.net> >> > > > Cc: "EMC-PCST (E-mail)" <emc-p...@majordomo.ieee.org> >> > > > Sent: Monday, January 15, 2001 5:42 PM >> > > > Subject: Re: Site Correlation >> > > > >> > > > >> > > >> >> > > >> Mr. Kwok's theories are logical and no doubt bear on the subject, > but >> > > > there >> > > >> is a historical angle that bears inspection. About the time FCC >> > limits >> > > > for >> > > >> IT equipment were being drawn up (late '70s) PCs were not yet on >> > > > everyone's >> > > >> desktop. Most of the business equipment that would have been >> > envisioned >> > > > to >> > > >> be qualified to USC Title 47, Part 15, Subpart J would have been >> > > > stand-alone >> > > >> items such a copier, with the only cable connection being ac power. >> > The >> > > >> report which documents the development of the CE and RE limits/test >> > > > methods >> > > >> found in the above mentioned FCC limits specifically states that 30 >> > MHz >> > > > was >> > > >> picked as the cutoff between CE and RE for the reason of radiation >> > > >> efficiency per Mr. Kwok's surmise, but also because 30 MHz was the >> > lowest >> > > >> frequency at which a 3 m OATS measurement would provide the desired >> > > >> accuracy. >> > > >> >> > > >> Ken Javor >> > > >> >> > > >> P.S. Said report also demonstrated that the CE limit below 30 MHz >> > > > sufficed >> > > >> to control RE from the power cable to levels sufficient to protect >> > against >> > > >> cable radiation-induced rfi. >> > > >> >> > > >> ---------- >> > > >> >From: Dan Kwok <dk...@intetron.com> >> > > >> >To: Ralph Cameron <ral...@igs.net> >> > > >> >Cc: "EMC-PCST (E-mail)" <emc-p...@majordomo.ieee.org> >> > > >> >Subject: Re: Site Correlation >> > > >> >Date: Mon, Jan 15, 2001, 2:49 PM >> > > >> > >> > > >> >> > > >> > >> > > >> > Hello Ralph: >> > > >> > >> > > >> > That's a good question. At one time, I pondered the same question >> > > >> > myself. There are obviously plenty of communication systems >> > operating >> > > >> > under 30 MHz. I suppose there are reasons why CISPR or CISPR 22 >> > does >> > not >> > > >> > specify radiated emissions below 30 MHz. I can suggest one >> > possibility. >> > > >> > Perhaps others here will come up with more. >> > > >> > >> > > >> > For a fixed cable of length L, the ratio of L/lambda gets >> > progressively >> > > >> > small for frequencies much less than 30 MHz with most commercial >> > EUTs. >> > > >> > If we consider the cable part of dipole antenna, the reduction in >> > > >> > frequency has a diminishing effect on the antenna's radiation >> > > >> > resistance. Given a constant current, the radiated power would >> > decrease >> > > >> > with decreasing radiation resistance. At 550 KHz (bottom of the > AM >> > > >> > broadcast band in North America), the 1/4 wavelength is 136 > meters. >> > Even >> > > >> > if the antenna's reactance is ignored, one would need very long >> > cables >> > > >> > driven by a significant CM noise voltage at this frequency to >> > radiate >> > > >> > much energy. >> > > >> > >> > > >> > -- >> > > >> >> > >> ------------------------------------------------------------------------ >> > > >> > Daniel Kwok >> > > >> > Principal EMC Engineer >> > > >> > Intetron Consulting, Inc. >> > > >> > Vancouver, Canada >> > > >> > Phone (604) 432-9874 >> > > >> > Email dk...@intetron.com >> > > >> > Web http://www.intetron.com"; >> > > >> > >> > > >> > >> > > >> > Ralph Cameron wrote: >> > > >> >> >> > > >> >> Ken: >> > > >> >> >> > > >> >> I like the idea of setting a limit to common mode currents on >> > attaching >> > > >> >> cables but mI wonder why CISPR has chosen to start such >> > measurements >> > at >> > > >> >> 30Mhz when most of the common mode currents are the result of >> > switching >> > > >> >> products and are generated harmonically from the fundamental > and >> > as >> > > > such >> > > >> >> propagate from the low Khz range up through 30Mhz. is there no >> > > > consideration >> > > >> >> for those who occupy the spectrum below 30Mhz? >> > > >> >> >> > > >> > >> > > >> > ------------------------------------------- >> > > >> > This message is from the IEEE EMC Society Product Safety >> > > >> > Technical Committee emc-pstc discussion list. >> > > >> > >> > > >> > 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: >> > > >> > Jim Bacher: jim_bac...@mail.monarch.com >> > > >> > Michael Garretson: pstc_ad...@garretson.org >> > > >> > >> > > >> > For policy questions, send mail to: >> > > >> > Richard Nute: ri...@ieee.org >> > > >> > >> > > >> > >> > > >> >> > > >> ------------------------------------------- >> > > >> This message is from the IEEE EMC Society Product Safety >> > > >> Technical Committee emc-pstc discussion list. >> > > >> >> > > >> 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: >> > > >> Jim Bacher: jim_bac...@mail.monarch.com >> > > >> Michael Garretson: pstc_ad...@garretson.org >> > > >> >> > > >> For policy questions, send mail to: >> > > >> Richard Nute: ri...@ieee.org >> > > >> >> > > >> >> > > >> >> > > > >> > > >> > >> > >> > ------------------------------------------- >> > This message is from the IEEE EMC Society Product Safety >> > Technical Committee emc-pstc discussion list. >> > >> > 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: >> > Jim Bacher: jim_bac...@mail.monarch.com >> > Michael Garretson: pstc_ad...@garretson.org >> > >> > For policy questions, send mail to: >> > Richard Nute: ri...@ieee.org >> > >> >> > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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