RE: Questions about EN61000-4-6
Hi Barry, I commend you on the in-dept study you do when looking at standards, but as Abraham Lincoln said, If you look for the bad ... you will surely find it. Standards are written for the majority of products, not for every product in every environment. That's why there is the TCF rout to compliance. Remember that we are ultimately not striving for compliance to standards, but to the EU Directives which does not give boundaries. It is impossible to write a standard that some what if wouldn't kill. So don't expect it to. But, don't think that because a test standard sets some boundaries that that's all there is to it. If you (your company) designs a product that 'by design' would be susceptible at some condition or frequency or in some likely environment that is not covered in a test standard you are still reasonable for its immunity performance per the Directive. Trying to determine what to test for is why us EMC engineers make the 'big bucks'. If you miss a problem area don't worry. It will show up at the customer site and then you can fix it. We had a product that passed all our immunity tests (even more strict than what the EU requires) but at one customer site the product would fail every day at the same time. What we found out was that they had a clock system that sent a pulse emission on the AC power line for the entire building to tell the clocks to advance to the hour and stop. Then a second pulse would tell all the clocks to start back up synchronizing them throughout the building. This pulse was unique enough to get past our Immunity tests. Are we legally required to make our products immune to this and all known emissions? Does the Directive give us an alternative? I believe we are obligated to design our products to be immune to any emission that it would 'Likely' see in the environments it will be used in which is always a moving target. But, would we burden the entire industry to be immune to a 'Clock Pluse' emisision that was only found at a few customer sites? Only YOU can answer that question, not the standards writter. As technology advances the environment our products much work in will be different than today. We as EMC engineers must be ready to do our jobs even when it requires us to go beyond the published standards. The people who are involved in writing standards have a difficult task. My hat goes off to them for their hard work. My hope is that I didn't offend anyone with my comments. Brian -Original Message- From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of Barry Ma Sent: Monday, March 27, 2000 6:33 PM To: EMC-PSTC Subject: Questions about EN61000-4-6 Hi Group, Here are some of my questions and thoughts about EN61000-4-6. Any corrections and comments are greatly appreciated. In discussion of Wisdom behind all these standards, Richard Nute summarized three points raised by Martin Rowe. One of them is reasonableness or appropriateness of the standard. Please allow me to have better understanding of reasonableness or appropriateness of the EN61000-4-6. Both EN61000-4-3 (4-3 in short below) and EN61000-4-6 (4-6) verify the immunity of EUT against induced disturbances caused by incident electromagnetic fields from 150 KHz to 1 GHz. The chamber test approach used in 4-3 is not suitable at lower frequencies (150 KHz to 80 MHz), - not in principle only technically. That's why we need to perform 4-6 differently from 4-3. The methodology of 4-6 is to inject conducted disturbance to cables connected to the EUT by using direct injection or clamp coupling. The injected cable currents are supposed to be the same as induced by incident electromagnetic fields in real world. The methodology of 4-6 also implies that at low frequencies the possible disturbance directly coupled into the EUT from incident electromagnetic fields can be ignored in comparison with the disturbance indirectly coupled to the EUT via attached cables. For many well-shielded EUT that assumption works because it is difficult for low frequency electromagnetic fields to directly get into the EUT through apertures (such as slots, seams, and holes), whose dimensions are small compared to wavelength. But what if the EUT has larger openings or only plastic enclosure? Let's see an extreme example. A component cannot work properly under the illumination of 2.5 V/m incident field at 50 MHz The component would feel 2.5 V/m field when installed if the EUT is illuminated by 3 V/m incident field. But the component could work OK if injecting cable current of 3V into the EUT. The boundary 80 MHz between 4-3 (80 to 1000 MHz) and 4-6 (0.15 to 80 MHz) is not always fixed. It may be adjusted depending on different scenario. That principle is mentioned only in principle. I would like to see a real example to adjust the boundary between 4-3 and 4-6. Does it make more sense to setup a transition region, say 50 to 100 MHz, for both 4-3 and 4-6 to overlap? For the same EUT the test level
RE: Questions about EN61000-4-6
CISPR 24 allows the transition from conducted to radiated immunity anywhere from 30MHz to 80MHz.. The European implementation, EN55024 does not. The 4-6, 4-3 boundary is at 80MHz. The Japanese did extensive testing for equivalence of RF field exposure to current injection. They found that above about 10MHz, the coupling falls as the log of the frequency. In other words, 3V/m does not equal 3V. This has been taken care of in CISPR 24. The test value of 3V was not changed but the limits were. John P. Wagner Lucent Technologies, Bell Labs 11900 N. Pecos St, Room 2F58 Denver CO 80234 email: johnwag...@lucent.com phone: 303 538-4241 fax: 303 538-5211 -- From: Barry Ma[SMTP:barry...@altavista.com] Reply To: Barry Ma Sent: Monday, March 27, 2000 4:32 PM To: EMC-PSTC Subject: Questions about EN61000-4-6 Hi Group, Here are some of my questions and thoughts about EN61000-4-6. Any corrections and comments are greatly appreciated. In discussion of Wisdom behind all these standards, Richard Nute summarized three points raised by Martin Rowe. One of them is reasonableness or appropriateness of the standard. Please allow me to have better understanding of reasonableness or appropriateness of the EN61000-4-6. Both EN61000-4-3 (4-3 in short below) and EN61000-4-6 (4-6) verify the immunity of EUT against induced disturbances caused by incident electromagnetic fields from 150 KHz to 1 GHz. The chamber test approach used in 4-3 is not suitable at lower frequencies (150 KHz to 80 MHz), - not in principle only technically. That's why we need to perform 4-6 differently from 4-3. The methodology of 4-6 is to inject conducted disturbance to cables connected to the EUT by using direct injection or clamp coupling. The injected cable currents are supposed to be the same as induced by incident electromagnetic fields in real world. The methodology of 4-6 also implies that at low frequencies the possible disturbance directly coupled into the EUT from incident electromagnetic fields can be ignored in comparison with the disturbance indirectly coupled to the EUT via attached cables. For many well-shielded EUT that assumption works because it is difficult for low frequency electromagnetic fields to directly get into the EUT through apertures (such as slots, seams, and holes), whose dimensions are small compared to wavelength. But what if the EUT has larger openings or only plastic enclosure? Let's see an extreme example. A component cannot work properly under the illumination of 2.5 V/m incident field at 50 MHz The component would feel 2.5 V/m field when installed if the EUT is illuminated by 3 V/m incident field. But the component could work OK if injecting cable current of 3V into the EUT. The boundary 80 MHz between 4-3 (80 to 1000 MHz) and 4-6 (0.15 to 80 MHz) is not always fixed. It may be adjusted depending on different scenario. That principle is mentioned only in principle. I would like to see a real example to adjust the boundary between 4-3 and 4-6. Does it make more sense to setup a transition region, say 50 to 100 MHz, for both 4-3 and 4-6 to overlap? For the same EUT the test level of 4-3 is 3V/m, and the test level of 4-6 is 3V (80% AM @ 1KHz). Is there any explanation or verification available to show the equivalence (even roughly) between these two levels in interferences with the EUT at boundary frequency? In real world all attached cables would have induced currents at the same time if an incident field illuminates upon the EUT. In 4-6 test procedure, however, all cables are injected one by one in turn. On the other hand, in Radiated Emission test we have to manipulate the placement of all attached cable to maximize the resultant emission from all cables. Is it fair? I mean there seems to be a double standard for Radiated Emission and Conducted Immunity. Best Regards, Barry Ma b...@anritsu.com For the largest MP3 index on the Web, go to http://mp3.altavista.com --- 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
Questions about EN61000-4-6
Hi Group, Here are some of my questions and thoughts about EN61000-4-6. Any corrections and comments are greatly appreciated. In discussion of Wisdom behind all these standards, Richard Nute summarized three points raised by Martin Rowe. One of them is reasonableness or appropriateness of the standard. Please allow me to have better understanding of reasonableness or appropriateness of the EN61000-4-6. Both EN61000-4-3 (4-3 in short below) and EN61000-4-6 (4-6) verify the immunity of EUT against induced disturbances caused by incident electromagnetic fields from 150 KHz to 1 GHz. The chamber test approach used in 4-3 is not suitable at lower frequencies (150 KHz to 80 MHz), - not in principle only technically. That's why we need to perform 4-6 differently from 4-3. The methodology of 4-6 is to inject conducted disturbance to cables connected to the EUT by using direct injection or clamp coupling. The injected cable currents are supposed to be the same as induced by incident electromagnetic fields in real world. The methodology of 4-6 also implies that at low frequencies the possible disturbance directly coupled into the EUT from incident electromagnetic fields can be ignored in comparison with the disturbance indirectly coupled to the EUT via attached cables. For many well-shielded EUT that assumption works because it is difficult for low frequency electromagnetic fields to directly get into the EUT through apertures (such as slots, seams, and holes), whose dimensions are small compared to wavelength. But what if the EUT has larger openings or only plastic enclosure? Let's see an extreme example. A component cannot work properly under the illumination of 2.5 V/m incident field at 50 MHz The component would feel 2.5 V/m field when installed if the EUT is illuminated by 3 V/m incident field. But the component could work OK if injecting cable current of 3V into the EUT. The boundary 80 MHz between 4-3 (80 to 1000 MHz) and 4-6 (0.15 to 80 MHz) is not always fixed. It may be adjusted depending on different scenario. That principle is mentioned only in principle. I would like to see a real example to adjust the boundary between 4-3 and 4-6. Does it make more sense to setup a transition region, say 50 to 100 MHz, for both 4-3 and 4-6 to overlap? For the same EUT the test level of 4-3 is 3V/m, and the test level of 4-6 is 3V (80% AM @ 1KHz). Is there any explanation or verification available to show the equivalence (even roughly) between these two levels in interferences with the EUT at boundary frequency? In real world all attached cables would have induced currents at the same time if an incident field illuminates upon the EUT. In 4-6 test procedure, however, all cables are injected one by one in turn. On the other hand, in Radiated Emission test we have to manipulate the placement of all attached cable to maximize the resultant emission from all cables. Is it fair? I mean there seems to be a double standard for Radiated Emission and Conducted Immunity. Best Regards, Barry Ma b...@anritsu.com For the largest MP3 index on the Web, go to http://mp3.altavista.com --- 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
