RE: Q on Correlation of Votage ripple with a Spectrum Analyser
Hi all, Actually I was using a good ole Spectrim Analyser so I sidestepped the windowing issue/software issues altogether. What I was(am)trying to do was match the max voltage as measured on a scope with the value as measured on a SA. I first calibrated myslef using a known source - a sine wave. The amplitudes fell in just as theory predicted. Encouraged, I then probed the Vcc plane on a product I was working on and was not so happy!! Any ideas? From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Saturday, July 26, 2003 4:19 PM To: Charles Grasso; Emc-Pstc Subject: Re: Q on Correlation of Votage ripple with a Spectrum Analyser I presented a paper on that very subject about a decade ago at one of the EMC TD magazine EMC symposia. I used a Fluke Scopemeter and some FFT software that came with it. The Fluke interfaced to the PC through an optically isolated RS-232 protocol. It worked quite well from a pre-compliance or troubleshooting point-of-view. You could use time windowing to separate the signals deriving from leading and falling edges from the signals deriving from the pulse itself. I used LISNMATE and LISNMARK mode separation devices to show that the rising/falling edge signals were common mode, while the pulse itself generated differential mode signals. From: Charles Grasso cgrassospri...@earthlink.net Reply-To: Charles Grasso cgrassospri...@earthlink.net Date: Sat, 26 Jul 2003 16:18:36 -0700 To: Emc-Pstc emc-p...@ieee.org Subject: Q on Correlation of Votage ripple with a Spectrum Analyser Hi All, Has anyone tried correlating the voltage ripple as seen on a scope with the amplitudes measured on a Spectrum Analyser? I tried doing that the other day with ..umm. minimal success. I think that due to the comples convoltions that would have to occur when FFT'ing an irregular voltage shape. Charles Grasso Echostar Communications. --- 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Q on Correlation of Votage ripple with a Spectrum Analyser
Charles Grasso wrote: What I was(am)trying to do was match the max voltage as measured on a scope with the value as measured on a SA. Try zero span on the SA. Compare THAT with the scope. Cortland 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Q on Correlation of Votage ripple with a Spectrum Analyser
I presented a paper on that very subject about a decade ago at one of the EMC TD magazine EMC symposia. I used a Fluke Scopemeter and some FFT software that came with it. The Fluke interfaced to the PC through an optically isolated RS-232 protocol. It worked quite well from a pre-compliance or troubleshooting point-of-view. You could use time windowing to separate the signals deriving from leading and falling edges from the signals deriving from the pulse itself. I used LISNMATE and LISNMARK mode separation devices to show that the rising/falling edge signals were common mode, while the pulse itself generated differential mode signals. From: Charles Grasso cgrassospri...@earthlink.net Reply-To: Charles Grasso cgrassospri...@earthlink.net Date: Sat, 26 Jul 2003 16:18:36 -0700 To: Emc-Pstc emc-p...@ieee.org Subject: Q on Correlation of Votage ripple with a Spectrum Analyser Hi All, Has anyone tried correlating the voltage ripple as seen on a scope with the amplitudes measured on a Spectrum Analyser? I tried doing that the other day with ..umm. minimal success. I think that due to the comples convoltions that would have to occur when FFT'ing an irregular voltage shape. Charles Grasso Echostar Communications. --- 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Q on Correlation of Votage ripple with a Spectrum Analyser
Hi All, Has anyone tried correlating the voltage ripple as seen on a scope with the amplitudes measured on a Spectrum Analyser? I tried doing that the other day with ..umm. minimal success. I think that due to the comples convoltions that would have to occur when FFT'ing an irregular voltage shape. Charles Grasso Echostar Communications. 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
pulse modulation in reverb chambers
List members, What is the limitation on minimum pulse width in reverberation chambers? I expect it relates to room size, but does anyone have either a functional relation or a rough order of magnitude? Light travels 300 meters per microsecond, so I would think a 1 microsecond pulse width would work just fine, but nanosecond rise-times would be lost. Thanks in advance for any inputs. Ken Javor 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: self blinking LEDs as EMI sources WAS: LED lamps
You are making the same argument Mr. Woodgate did, but adding another mechanism for creating the rf emission. Note that I did not offer an explanation of the source of an rf emission, I simply postulated its existence. Then I stated my point of departure from Mr. Woodgate's analysis, which was that even given an rf emission, I didn't believe that would be sufficient to interfere with a wired handset on a land line. Mr. Woodgate subsequently humorously commented regarding my assertion (that this would be a more credible problem if the handset were a cordless link). And his comment was right on target. If that actually was the case, and it was not mentioned in the original posting, then Mr. Wan Juang Foo deserves 50 lashings with a wet noodle, or the proper cyberspace equivalent. The underlying point I was making was that it is not enough to have an rf emission, you have to have a victim sensitive enough to pick it up and respond. An rf emission even 30 dB over the limit should not cause problems except at a radio's tuned frequency, or to very sensitive instrumentation, such as you might have monitoring brain waves during surgery. And that last assumes an unintentional demodulation capability. From: Cortland Richmond 72146@compuserve.com Date: Sat, 26 Jul 2003 13:06:25 -0400 To: Ken Javor ken.ja...@emccompliance.com, ieee pstc list emc-p...@ieee.org Subject: Re: self blinking LEDs as EMI sources WAS: LED lamps Ken Javor wrote: ... but I wonder if the presence of even an rf emission (as contrasted to 50 Hz) should cause any problem to a land-line phone with a wired handset. It wouldn't seem likely that the power available from a couple AA batteries would be sufficient for that. Now if it were a cordless phone and there were an rf emission in band to the cordless link, that would be much more credible. I'd lean towards a more prosaic explanation; oscillations involving the transistors which make the LED's blink. During the inevitable time in a linear region of operation while switching, they may well be oscillating at frequencies determined by the length of the wires to which they are connected. This would last only a short time, of course, but would generate a narrow RF pulse which might well be rectified in a nearby audio amplifier. Cortland 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: self blinking LEDs as EMI sources WAS: LED lamps
I read in !emc-pstc that Ken Javor ken.ja...@emccompliance.com wrote (in bb480cc1.366c%ken.ja...@emccompliance.com) about 'self blinking LEDs as EMI sources WAS: LED lamps' on Sat, 26 Jul 2003: I agree with most of Mr. Woodgate's commentary, but I wonder if the presence of even an rf emission (as contrasted to 50 Hz) should cause any problem to a land-line phone with a wired handset. It wouldn't seem likely that the power available from a couple AA batteries would be sufficient for that. It's maybe a question of proximity, but I agree that I was reaching for an explanation. Now if it were a cordless phone and there were an rf emission in band to the cordless link, that would be much more credible. The OP didn't mention that: if it is, it reminds me of the story of the sailor who reported to a newspaper that his broken leg had been cured in three days by wrapping it in oakum and tarring it. After many protestations of disbelief, he disclosed that the leg was made of wood. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: self blinking LEDs as EMI sources WAS: LED lamps
Ken Javor wrote: ... but I wonder if the presence of even an rf emission (as contrasted to 50 Hz) should cause any problem to a land-line phone with a wired handset. It wouldn't seem likely that the power available from a couple AA batteries would be sufficient for that. Now if it were a cordless phone and there were an rf emission in band to the cordless link, that would be much more credible. I'd lean towards a more prosaic explanation; oscillations involving the transistors which make the LED's blink. During the inevitable time in a linear region of operation while switching, they may well be oscillating at frequencies determined by the length of the wires to which they are connected. This would last only a short time, of course, but would generate a narrow RF pulse which might well be rectified in a nearby audio amplifier. Cortland 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: self blinking LEDs as EMI sources WAS: LED lamps
I agree with most of Mr. Woodgate's commentary, but I wonder if the presence of even an rf emission (as contrasted to 50 Hz) should cause any problem to a land-line phone with a wired handset. It wouldn't seem likely that the power available from a couple AA batteries would be sufficient for that. Now if it were a cordless phone and there were an rf emission in band to the cordless link, that would be much more credible. From: John Woodgate j...@jmwa.demon.co.uk Reply-To: John Woodgate j...@jmwa.demon.co.uk Date: Sat, 26 Jul 2003 10:38:36 +0100 To: emc-p...@majordomo.ieee.org Subject: Re: self blinking LEDs as EMI sources WAS: LED lamps I read in !emc-pstc that Wan Juang Foo f...@np.edu.sg wrote (in of7340f59a.f0a87124-on48256d6f.000df921-48256d6f.0013d...@np.edu.sg) about 'self blinking LEDs as EMI sources WAS: LED lamps' on Sat, 26 Jul 2003: These circuits were found to (well at any rate, seems to) emit interference that cause a telephone to pick up (50Hz) hum! Up to that point, your treatment of the phenomenon was quite scientific. It looks like the mains hum was pick up and modulated by the 'device' and reradiated or broadcasted... I think that is improbable. For such a small circuit to pick up significant mains hum, the magnetic field would have to be very strong, but in that case, why did not the circuits in the telephone, which are much larger in area, pick up the hum directly? Then again, such a small circuit as you describe for the LEDs would not re-radiate significantly at 50 Hz. And the presence of a flashing LED would seem to play no part in any re-radiation. You don't say that the hum was modulated on/off or in level in time with the flashing of the LED, and if there were no such modulation, that would seem to confirm that the LED circuit was not causing the hum. The situation might be different if the LED circuit included a precision timer, based on a high-frequency clock. This might radiate over short distances, and the radiation *might* be modulated by quite a small voltage induced by a weak 50 Hz magnetic field. In that case, you should be able to find the high-frequency emission with a spectrum analyser and sniffer loop, or a scanning receiver, whether or not the 50 Hz field is present. But the induced hum would be modulated at the flash rate. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: self blinking LEDs as EMI sources WAS: LED lamps
I read in !emc-pstc that Wan Juang Foo f...@np.edu.sg wrote (in of7340f59a.f0a87124-on48256d6f.000df921-48256d6f.0013d...@np.edu.sg) about 'self blinking LEDs as EMI sources WAS: LED lamps' on Sat, 26 Jul 2003: These circuits were found to (well at any rate, seems to) emit interference that cause a telephone to pick up (50Hz) hum! Up to that point, your treatment of the phenomenon was quite scientific. It looks like the mains hum was pick up and modulated by the 'device' and reradiated or broadcasted... I think that is improbable. For such a small circuit to pick up significant mains hum, the magnetic field would have to be very strong, but in that case, why did not the circuits in the telephone, which are much larger in area, pick up the hum directly? Then again, such a small circuit as you describe for the LEDs would not re-radiate significantly at 50 Hz. And the presence of a flashing LED would seem to play no part in any re-radiation. You don't say that the hum was modulated on/off or in level in time with the flashing of the LED, and if there were no such modulation, that would seem to confirm that the LED circuit was not causing the hum. The situation might be different if the LED circuit included a precision timer, based on a high-frequency clock. This might radiate over short distances, and the radiation *might* be modulated by quite a small voltage induced by a weak 50 Hz magnetic field. In that case, you should be able to find the high-frequency emission with a spectrum analyser and sniffer loop, or a scanning receiver, whether or not the 50 Hz field is present. But the induced hum would be modulated at the flash rate. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
self blinking LEDs as EMI sources WAS: LED lamps
Dear All, I observe recently that some self blinking (and color changing) LEDs 'are' what seem to be a substantial emitters of radiated emission/interference. These LEDs are rigged up by hobbyists as decorative illuminators and acts more or less like the blinking lights for Christmas trees. I observe that each of theses circuits can be made to hung like Christmas tree ornaments. I came across a situation where the telephone lines were 'substantially noisier' :-) when several sets of battery operated circuits was about 3 m away from the telephone. It is not a very scientific method but I did a quick check and found by the method of elimination ;-) or what some would call systematic trials to find the source of the problem. It took me by surprise that the LEDs had a substantial role to play in the interference. LED circuits gets connected (on), hum gets louder. LEDs circuits gets disconnected, hums gets quieter and so on and so forth... These are very simple circuits with a single resistor and the LED in series. The 2 AA sized NiCad battery with holder, single resistor and LED including wire, total length about 5, tip to tip. These circuits were found to (well at any rate, seems to) emit interference that cause a telephone to pick up (50Hz) hum! It looks like the mains hum was pick up and modulated by the 'device' and reradiated or broadcasted... I can see that the blinking action at about 1 Hz have a duty cycle and that may generate a lot of ringing but what is surprising is the interference finding its way into the a telephone handset! I find it hard to believe that how the 'carrier' of the mains hum can eventually gets demodulated a puzzle. One wonders what can be observed if I get the circuits to a OATS? There again, how do I recreate the 50 Hz environment to couple the mains into these LED circuit? I had the Helmholtz coil in mind but can that be 'treated' as part of a test setup? Did anyone here have similar observation? One wonders if there any 'product specific standards' for such battery operated device that uses LEDs as decorative illuminators. :-) One wonders what will happen if there are such gadgets line up to 'hit' the market this Christmas... Looks like there will be a lot of testing work coming for EMC engineers! Tim Foo 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
