FCC + FCC = FCC?
Hi Group This is a question regardinga plug in PC card that has been stated as FCC compliant which is inserted in a PC that is also stated to be FCC compliant and theemissions are found to actually exceed the FCC limits. What is the responsibility of the manufacturer who is intending to place this on the market as a functional unit? Are they liable for the overall unit or can they sell on the basis that it comprises FCC compliant sub assemblies, albeit evidently originally tested in different configurations. If they are liable, how can anyone sell any PC/PC card combination considering that the card could have originally been tested in a so called golden PC. Many thanks John CroninGet Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on "Virtual Conference Hall,"
Re: You won't believe this ... Well, maybe you will.
Hi Doug: done, the entire safety approval reduced to a simple cfm rating fan for a chip both on the secondary side of the power supply. The issue for me is: What is the safety requirement that requires cfm (I presume a minimum cfm)? Reading between the lines... The fan cools the chip. The chip runs warm/hot and requires forced-air cooling. The chip heats the printed wiring board on which it is mounted. The temperature of the printed wiring board is a function of the power dissipated by the chip and by the cooling of the chip. Without the cooling, the PWB temperature would exceed the limits specified in the standard. So, I presume the safety requirement is that of temperature of the PWB. Without the fan, the PWB temperature would rise above the limit value specified in the standard. For the purposes of safety, nobody cares whether the fan is effective at cooling the chip, or even if the chip gets so hot as to self-destruct. We are only concerned with the temperature of the PWB. Working with these data, I see a number of ways out of this predicament. 1. Control the fan by manufacturer's name and model number. The cfm is not necessary. We simply know by test that the cooling provided by this specific fan is sufficient to keep the PWB from exceeding the allowable limit. (Since the fan is a secondary circuit motor, you will have to comply with those requirements, but they are a separate issue to that of the PWB temperature.) 2. Control the fan by electrical ratings and physical size. The electrical ratings (power) are proportional to cfm. 3. Exempt the secondary PWB from the temperature requirements. Since the PWB is a secondary circuit (I presume SELV), then there is no shock hazard in the event of failure of the PWB insulation. So, the PWB provides no safety function in terms of electric shock, and therefore the temperature requirements need not apply. However, failure of the fan is an abnormal/fault condition for determining fire hazard. So, the unit must be tested for 7 hours without the fan running to determine no fire. So, I'm wondering some of the following: 1. Have any you ever run into something like this before? 2. If you have, what did you do about it? I have not answered your questions. But, I often invoke these kinds of reasonings so that we don't get stuck with traditional or single solutions that otherwise would be onerous or impossible. Best regards, Rich --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
Products Electrical Ratings De-rated for Eurpoean Branch Circuits
Does anyone know if it is common practice or otherwise required to de-rate products in Europe to 80% (or some other %) of the rating of the branch circuit as is done in the US? Some product standards (such as 61000-3-2) apply to products rated up to 16A, so it would appear that products can be rated up to the branch rating. If this is the case, would it be acceptable to exceed the rating by 110% (as allowed by 60950) and still be usable on that branch circuit? Regards, Glenn Lesmeister Product Regulatory Compliance Compaq Computer Corp. Tel: 281-514-5163 20555 SH 249, MS60607 Fax: 281-514-8029 Houston, TX 77070-2698 Pgr: 713-786-4930 glenn.lesmeis...@compaq.com I am empowered to do what makes sense! --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
You won't believe this ... Well, maybe you will.
Dear all, In bringing a product through safety and having many issues, it might surprise you that after all was said and done, the entire safety approval reduced to a simple cfm rating fan for a chip both on the secondary side of the power supply. For some obvious reasons of which I hope you all understand, I can't provide too many details either here or off-line. Needless to say, the fan and chip companies have non-disclosure agreements them. In trying to obtain a simple cfm rating of the fan, a flurry of call the other guy began to happen. Nothing was resolved. Indeed, I went so far as to offer signing ANY type of non-disclosure agreements with both of them. But that was to no avail. And it remains so. So, the ECO gets cut to remove that part and mfr, plus any other parts by said mfr. An email gets sent to said fan company stating the resultant actions, etc, etc ... I doubt it will be of any concern to them. My reason for posting is that in the 20 or so years of doing EMC/Safety, I've never run into such a thing. Neither have I heard such a thing from associates who have been doing this work for as long or longer than I. This isn't an invitation to a bitch session about the companies. Nor is it a complaint about the NRTLs who are just doing their job. My experience in said matter with the NRTL has been great. I've run into something similar with patents and ink believe it or not. Mfr.'s are not really obligated to spell out exactly everything in something such as a patent, which I found surprising. What surprises me here is in the case of safety, where information is not disclosed. The NRTL didn't do cfm rating of the fan. In fact, there's really little no standard way to do cfm of fans. Thus, the reason why they allow similar fans within a mfr but not from another mfr. in some cases. So, I'm wondering some of the following: 1. Have any you ever run into something like this before? 2. If you have, what did you do about it? On and off line responses both welcome ... Regards, Doug McKean --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
RE: braided vs served shields
This might not directly answer your question, but may put some light on why these questions are difficult to answer in general. For all cables , the transfer impedance is equal to the Ohmic resistance of the shield at low frequencies. At higher frequencies the braiding effect causes due to the rotating effect of the braiding magnetic field line escape in a direction 90 degrees on the cable. This is additional self inductance that must be added to the transfer ohmic resistance, so at high frequencies the transfer resistance becomes a complex impedance At even higher frequencies the shield cuts itself in an inner shield for the signal current and an outer shield for interference current, due to the skin effect. ( this greatly improves the shielding quality) This of course at frequencies where the skin depth is much smaller then the effective depth of the shield. The braiding effect creates here a problem as the wires change with every cm from in- to outside of the shield. The (skin) current WILL stay outside and has to cross from wire to wire. Here oxidation will change cable properties when cable gets old. Spiral (foil) shields rely on these contacts between windings to avoid heavy self induction effects due to the winding of the spiral. As the ohmic resistance is higher as copper, at LOWER frequencies these shields are inferior to braided ones. There are however, much less contact points per cm as the braided cable but many contact SURFACE exists so capacitive coupling between spiral winding will reside at high frequencies where oxidation might impair contact resistance. In general these cables do well at high frequencies where self induction part of the transfer impedance is much dominant and where oxidation might happen. Often these shields are combined with a braided shield to get the best of both worlds. Best of all is the massive shield , (semi rigid cable). Regards, Gert Gremmen, (Ing) ce-test, qualified testing === Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ === -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of brent.dew...@us.datex-ohmeda.com Sent: Monday, June 18, 2001 10:55 PM To: emc-p...@majordomo.ieee.org Subject: braided vs served shields Does anyone have any references or data on the comparative transfer impedance between served (spiral) and braided cable shielding at the same coverage level? Thanks! Brent DeWitt --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall, attachment: Gert Gremmen.vcf
RE: ISO TR 10605 test setup (ESD)
Just one more comment: You never want a separate ground to a GRP that is different from other grounds in the building and more importantly, in the test area. There is a real risk of the GRP being at a different potential than other grounds, even if it is connected to a ground rod. Others have measured significant potentials between separate grounds in the same building.. Mike Hopkins KeyTek -Original Message- From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Tuesday, June 19, 2001 8:46 AM To: 'Chris Chileshe'; emc-p...@majordomo.ieee.org Subject: RE: ISO TR 10605 test setup (ESD) Hi from one Chris to another, I'm going to address your ground rod concerns (Question 3). In our lab here, we have a new building with new wiring and a reliable third wire Earth ground, so I simply tie my Ground Reference Plane (GRP) to the third wire of one of the AC outlets in the room. I have a cable from the GRP to the outlet with a ring lug. The ring lug is screwed to the ground connection with a lock washer and screw. I occassionally verify this ground connection with a ohmmeter. All devices under test are plugged into these same AC outlets (unless they're battery powered), so my GRP is common with all of my device under test Earth ground connections. If you used a doctored plug, the only concern that I would have would be with regard to the connection coming loose. However, I noticed that you're in the UK where they use that three pound broad sword for the AC ground terminal. It would probably take an earthquake to loosen that thing. But, I would still verify the connection with an ohmmeter. I have talked to many people about this; and this is the collective rationale that I have gathered. An ESD test setup needs to have a stable reference potential set by the GRP. The ESD gun's ground strap is tied to the GRP and all discharge potentials are then referenced to the GRP. Since the GRP is large and wide; it has low inductance along with a large amount of free space capacitance. The GRP is a very good high frequency ground potential. This means that the GRP's potential won't change much when the ESD current is bled into it. This keeps results repeatable. Just by having a GRP, you have satisfied 99% of the grounding requirements for a good ESD test . Now, why tie the GRP to Earth? The GRP's connection to Earth ground serves two purposes. It is a low frequency ground connection to ensure that, over time, the GRP's DC potential won't change with respect to Earth ground. The GRP's Earth ground connection also ensures that the GRP has a low frequency common with any Earth grounds that the device under test may have. It is my belief that you don't need a dedicated ground rod for your ESD setup to satisfy this requirement. My opinions only; not to be confused with fact, company policy or gospel under any circumstance :-) Chris Maxwell Design Engineer - NetTest Optical Division email chris.maxw...@nettest.com phone +1 315 266 5128 fax +1 315 797 8024 NetTest 6 Rhoads Drive, Utica, NY 13502 USA web www.nettest.com -Original Message- From: Chris Chileshe [SMTP:chris.chile...@ultronics.co.uk] Sent: Tuesday, June 19, 2001 5:22 AM To: emc-p...@majordomo.ieee.org Subject: ISO TR 10605 test setup (ESD) Hi group For those of you unfamiliar with ISO TR 10605, it is the ESD test standard for automotive electronics (8kV contact, 25kV air). I am trying to perform quick ESD tests on a product which has bottom entry proprietary cable. Picture if you an upside-down bottle of coke with push buttons at the top and cable entry at the bottom end. The cable itself is screened multicore with a molded end connector so there is a minimum length it must protrude from the product before it even thinks about bending. This is about an inch and a half (about 40mm). According to ISO TR 10605, if insulation is required under the EUT, the insulation must support the EUT some 25mm above the ground plane. Question 1: Does this insulation have to be 25mm thick or can I make a table like structure with thinner insulating sheet and supporting pillars at the corners? Question 2: Would a more 'compliant' test set-up have the bottle of coke lying on its side rather than standing vertically as it would in practice? The setup for the ESD test shows a ground strap connect the plane to a grounding rod. We had a specialised ESD test area where I worked before but we took everything for granted and didn't really bother finding out where or how the ground connection was made! Question 3: Can I connect the ground strap via say a UK 3-pin plug (with live and neutral prongs removed) into a mains socket or is this asking for trouble (RCD's etc). Grateful for any advice Regards - Chris Chileshe _ This message has been checked for all known viruses by Star
Re: ISO TR 10605 test setup (ESD)
83d652574e7af740873674f9fc12dbaa675...@utexh1w2.gnnettest.com, Chris Maxwell chris.maxw...@nettest.com inimitably wrote: The GRP's connection to Earth ground serves two purposes. It is a low frequency ground connection to ensure that, over time, the GRP's DC potential won't change with respect to Earth ground. The GRP's Earth ground connection also ensures that the GRP has a low frequency common with any Earth grounds that the device under test may have. It is my belief that you don't need a dedicated ground rod for your ESD setup to satisfy this requirement. Is right what he say. Refer everything in the test set-up to the GRP and just run a drain wire to the mains earth. -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
Re: Clock dithering
tkrepdavsml7e...@jmwa.demon.co.uk, John Woodgate j...@jmwa.demon.co.uk inimitably wrote: 4.3.2.7.2.20010618143751.00b3d...@box.tin.it, Paolo Roncone paolo...@tin.it inimitably wrote: As for interference to broadband receivers (like TV equipment) I remember a Lexmark study published a few years ago that showed no increased interference from modulated clocks vs unmodulated clocks (there was also a related discussion in this forum a while ago). That is correct, as far as it goes. Dithered clocks do not cause extra interference to *analogue* TV I honestly don't know if anything new came up recently. What came up was *digital* TV (European system). This does show unexpected sensitivity to dithered clocks. Searching for something else today, I found my original proposal to BSI for a CISPR study of the subject. It is dated 9 April 1998, and that is the date that BSI circulated it to the relevant committee. The mills of God and standards -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
May, 2001 EMC/Telco/Product Safety Update Now Available
The Curtis-Straus Update is for May, 2001 is now available at: http://www.conformity-update.com The headlines are: THE EU, RTTE AND TRANSITION RULES. UPDATE ON THE US/EU MEDICAL DEVICE MRA. EC STANDS PAT ON FLAME RETARDANTS IN PLASTIC. BUSH TAKES CONTROL AT THE FCC. FCC TO AUDIT 25% OF TCB GRANTS. OSHA, NOW UNDER BUSH, SAYS IT WON'T BE IGNORED. MORE ON THE CPSC'S AGGRESSIVE MOVES AGAINST MANUFACTURERS. UPDATED LIST OF NOTIFIED BODIES PUBLISHED. EVERYTHING YOU WANTED TO KNOW ABOUT THE IEC'S EMC STANDARDS. IEC/CISPR/ANSI STANDARDS UPDATE. UL STANDARDS UPDATE. FCC MOURNS THE PASSING OF CHANG. MEETINGS, SEMINARS, ETC. --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
RE: ISO TR 10605 test setup (ESD)
Hi from one Chris to another, I'm going to address your ground rod concerns (Question 3). In our lab here, we have a new building with new wiring and a reliable third wire Earth ground, so I simply tie my Ground Reference Plane (GRP) to the third wire of one of the AC outlets in the room. I have a cable from the GRP to the outlet with a ring lug. The ring lug is screwed to the ground connection with a lock washer and screw. I occassionally verify this ground connection with a ohmmeter. All devices under test are plugged into these same AC outlets (unless they're battery powered), so my GRP is common with all of my device under test Earth ground connections. If you used a doctored plug, the only concern that I would have would be with regard to the connection coming loose. However, I noticed that you're in the UK where they use that three pound broad sword for the AC ground terminal. It would probably take an earthquake to loosen that thing. But, I would still verify the connection with an ohmmeter. I have talked to many people about this; and this is the collective rationale that I have gathered. An ESD test setup needs to have a stable reference potential set by the GRP. The ESD gun's ground strap is tied to the GRP and all discharge potentials are then referenced to the GRP. Since the GRP is large and wide; it has low inductance along with a large amount of free space capacitance. The GRP is a very good high frequency ground potential. This means that the GRP's potential won't change much when the ESD current is bled into it. This keeps results repeatable. Just by having a GRP, you have satisfied 99% of the grounding requirements for a good ESD test . Now, why tie the GRP to Earth? The GRP's connection to Earth ground serves two purposes. It is a low frequency ground connection to ensure that, over time, the GRP's DC potential won't change with respect to Earth ground. The GRP's Earth ground connection also ensures that the GRP has a low frequency common with any Earth grounds that the device under test may have. It is my belief that you don't need a dedicated ground rod for your ESD setup to satisfy this requirement. My opinions only; not to be confused with fact, company policy or gospel under any circumstance :-) Chris Maxwell Design Engineer - NetTest Optical Division email chris.maxw...@nettest.com phone +1 315 266 5128 fax +1 315 797 8024 NetTest 6 Rhoads Drive, Utica, NY 13502 USA web www.nettest.com -Original Message- From: Chris Chileshe [SMTP:chris.chile...@ultronics.co.uk] Sent: Tuesday, June 19, 2001 5:22 AM To: emc-p...@majordomo.ieee.org Subject: ISO TR 10605 test setup (ESD) Hi group For those of you unfamiliar with ISO TR 10605, it is the ESD test standard for automotive electronics (8kV contact, 25kV air). I am trying to perform quick ESD tests on a product which has bottom entry proprietary cable. Picture if you an upside-down bottle of coke with push buttons at the top and cable entry at the bottom end. The cable itself is screened multicore with a molded end connector so there is a minimum length it must protrude from the product before it even thinks about bending. This is about an inch and a half (about 40mm). According to ISO TR 10605, if insulation is required under the EUT, the insulation must support the EUT some 25mm above the ground plane. Question 1: Does this insulation have to be 25mm thick or can I make a table like structure with thinner insulating sheet and supporting pillars at the corners? Question 2: Would a more 'compliant' test set-up have the bottle of coke lying on its side rather than standing vertically as it would in practice? The setup for the ESD test shows a ground strap connect the plane to a grounding rod. We had a specialised ESD test area where I worked before but we took everything for granted and didn't really bother finding out where or how the ground connection was made! Question 3: Can I connect the ground strap via say a UK 3-pin plug (with live and neutral prongs removed) into a mains socket or is this asking for trouble (RCD's etc). Grateful for any advice Regards - Chris Chileshe _ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call 01285 884400. --- 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: Michael Garretson:pstc_ad...@garretson.org
ISO TR 10605 test setup (ESD)
Hi group For those of you unfamiliar with ISO TR 10605, it is the ESD test standard for automotive electronics (8kV contact, 25kV air). I am trying to perform quick ESD tests on a product which has bottom entry proprietary cable. Picture if you an upside-down bottle of coke with push buttons at the top and cable entry at the bottom end. The cable itself is screened multicore with a molded end connector so there is a minimum length it must protrude from the product before it even thinks about bending. This is about an inch and a half (about 40mm). According to ISO TR 10605, if insulation is required under the EUT, the insulation must support the EUT some 25mm above the ground plane. Question 1: Does this insulation have to be 25mm thick or can I make a table like structure with thinner insulating sheet and supporting pillars at the corners? Question 2: Would a more 'compliant' test set-up have the bottle of coke lying on its side rather than standing vertically as it would in practice? The setup for the ESD test shows a ground strap connect the plane to a grounding rod. We had a specialised ESD test area where I worked before but we took everything for granted and didn't really bother finding out where or how the ground connection was made! Question 3: Can I connect the ground strap via say a UK 3-pin plug (with live and neutral prongs removed) into a mains socket or is this asking for trouble (RCD's etc). Grateful for any advice Regards - Chris Chileshe _ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call 01285 884400. --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
Re: braided vs served shields
of8e69fc62.4b791cdf-on87256a6f.0070d...@us.datex-ohmeda.com, brent.dew...@us.datex-ohmeda.com inimitably wrote: Does anyone have any references or data on the comparative transfer impedance between served (spiral) and braided cable shielding at the same coverage level? It's heavily frequency-dependent. At low frequencies, it's the end-to- end resistance that matters. As the frequency goes up, more energy can penetrate, but that depends on the dimensions of the gaps between the wires, and especially whether the spiral shielding has short-circuits between adjacent turns or not. -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
Re: Clock dithering
200106182001.qaa14...@interlock2.lexmark.com, rogle...@lexmark.com inimitably wrote: According to our extensive tests in conjunction with Philips Consumer Electronics, digital TV (both COFDM and ATSC) is actually less susceptible to interference from spread spectrum clocks (ssc) than current analog TV (both PAL and NTSC). Well, I hope someone will take those results to the CISPR study, instead of declining to participate and fuming with frustration in the background, as has happened with other EMC issues in the past. -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
Re: Clock dithering
4.3.2.7.2.20010618143751.00b3d...@box.tin.it, Paolo Roncone paolo...@tin.it inimitably wrote: As for interference to broadband receivers (like TV equipment) I remember a Lexmark study published a few years ago that showed no increased interference from modulated clocks vs unmodulated clocks (there was also a related discussion in this forum a while ago). That is correct, as far as it goes. Dithered clocks do not cause extra interference to *analogue* TV I honestly don't know if anything new came up recently. What came up was *digital* TV (European system). This does show unexpected sensitivity to dithered clocks. -- Regards, John Woodgate, OOO - Own Opinions Only. Phone +44 (0)1268 747839 Fax +44 (0)1268 777124. http://www.jmwa.demon.co.uk Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? --- 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: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net 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://www.rcic.com/ click on Virtual Conference Hall,
