RE: Radiated Emissions setup
Worse arrangement obtainable within the prescribed set-up. e. g. peripherals 10 cm apart, equipment aligned with the table edge, and excess cable bundled above the ground plane et al as described in C63.4 and CISPR 22 (or 16?). There was a time when it was just plain worse arrangement. In that case you had an X factorial number of combinations to play with. CPU, mouse, printer, modem: cpu, printer, mouse, modem: cpu printer, modem mouse, et all. I'll be darned if I remember what all we had attached but it had 10 peripherals and that was a grand total of over 3 million combinations if one followed the directions literally. There also was the consultant who when called to the FCC test site to explain a test failure found that the FEDS had taken the keyboard cables and wrapped it around the monitor. An operator would have had to stare through the cables to read the screen.Heavy sigh! (Could just be urban legend but it matches a pattern in the beginning of commercial EMC measurements of 1982. Good people but a little overzealous at times. Gary -Original Message- From: michael.sundst...@nokia.com [mailto:michael.sundst...@nokia.com] Sent: Tuesday, August 20, 2002 12:56 PM To: robert.s...@flextronics.com; alex.mcn...@ingenicofortronic.com; emc-p...@majordomo.ieee.org Subject: RE: Radiated Emissions setup The cable layout is required to be the 'worst case' attainable, isn't it? Michael Sundstrom NOKIA TCC Dallas / EMC ofc: (972) 374-1462 cell: (817) 917-5021 amateur call: KB5UKT -Original Message- From: ext robert.s...@flextronics.com [mailto:robert.s...@flextronics.com] Sent: Tuesday, August 20, 2002 1:05 PM To: alex.mcn...@ingenicofortronic.com; emc-p...@majordomo.ieee.org Subject: RE: Radiated Emissions setup Neil, I would like to see the pictures of your audit board. Without seeing the pictures I have the following comments. 1. I think this is a very good idea from a repeatability standpoint and I would like to consider adopting it. 2. It may be more trouble than simply draping the cables over the table edge, but less than bundling them properly. 3. Some of our customers bring their products in already attached to such a board with their cables all fastened securely in configurations accepted by their customers. This also lessens the setup time and gets them in and out quicker. 4. I believe that Note 1 of Figure 10 in EN 55022 refers to cables which connect one piece of gear on the table to another. If the cables were cut, it would require splicing or installing connectors. If a shorter cable were used, it may not represent actual use. I feel that generally customers having a two meter cable which is longer than needed would either drape it to the floor (which is not normally a metal ground plane), or bundle it neatly to keep it out of the way. On the other hand, since we as testers never know how equipment will be configured, the demand for repeatability requires that a system such as that described in Figure 10 be used. Robert Seay -Original Message- From: Alex McNeil [mailto:alex.mcn...@ingenicofortronic.com] Sent: Tuesday, August 20, 2002 12:00 PM To: 'emc-p...@majordomo.ieee.org' Subject:Radiated Emissions setup Hi Forum, As we all know test setups are absolutely critical to EMC results. I have the good fortune of having a good pre-compliance radiated emissions site (3m OATS, Fully or Semi Anechoic Chamber). From using this site I see all sorts of "funnies" but still the most annoying is how much you can change the emission results just by changing cable positions. I carry out regular EMC audits and could never quite get the same results as 6 months previous, when that particular product was last tested (I keep the master product and was still getting different results due to setup). I now use an "Audit" board where I bundle the cables (30-40cm) in a particular "figure of 8" fashion via fixed wooden pegs. Thru' time I have convinced myself that this not only gives me worst case emissions but also that much sought after REPEATABILITY! I believe the setup is as per EN55022. I have a photograph* of this Audit board to allow this forum to comment on the good and the bad points of using such a system. Also, is there any reason I cannot take this Audit board to a Test House for Product Compliance testing and at the same time get correlation between a Compliance site and my own site? Photograph details (EUT with 3 X Serial Ports, PSTN and DC SELV power connection) 1. The 1M, 2M and 3M indicate the Horizontal bundling of cables from RS232 ports which would go to a tabletop EUT peripheral (or leave open circuit). The 3 lengths are connected to similar ports. This covers the different lengths issues. 2. The P is the inline power supply O/P cable going to the EUT. This is bundled vertically
RE: Radiated Emissions setup
The cable layout is required to be the 'worst case' attainable, isn't it? Michael Sundstrom NOKIA TCC Dallas / EMC ofc: (972) 374-1462 cell: (817) 917-5021 amateur call: KB5UKT -Original Message- From: ext robert.s...@flextronics.com [mailto:robert.s...@flextronics.com] Sent: Tuesday, August 20, 2002 1:05 PM To: alex.mcn...@ingenicofortronic.com; emc-p...@majordomo.ieee.org Subject: RE: Radiated Emissions setup Neil, I would like to see the pictures of your audit board. Without seeing the pictures I have the following comments. 1. I think this is a very good idea from a repeatability standpoint and I would like to consider adopting it. 2. It may be more trouble than simply draping the cables over the table edge, but less than bundling them properly. 3. Some of our customers bring their products in already attached to such a board with their cables all fastened securely in configurations accepted by their customers. This also lessens the setup time and gets them in and out quicker. 4. I believe that Note 1 of Figure 10 in EN 55022 refers to cables which connect one piece of gear on the table to another. If the cables were cut, it would require splicing or installing connectors. If a shorter cable were used, it may not represent actual use. I feel that generally customers having a two meter cable which is longer than needed would either drape it to the floor (which is not normally a metal ground plane), or bundle it neatly to keep it out of the way. On the other hand, since we as testers never know how equipment will be configured, the demand for repeatability requires that a system such as that described in Figure 10 be used. Robert Seay -Original Message- From: Alex McNeil [mailto:alex.mcn...@ingenicofortronic.com] Sent: Tuesday, August 20, 2002 12:00 PM To: 'emc-p...@majordomo.ieee.org' Subject:Radiated Emissions setup Hi Forum, As we all know test setups are absolutely critical to EMC results. I have the good fortune of having a good pre-compliance radiated emissions site (3m OATS, Fully or Semi Anechoic Chamber). From using this site I see all sorts of "funnies" but still the most annoying is how much you can change the emission results just by changing cable positions. I carry out regular EMC audits and could never quite get the same results as 6 months previous, when that particular product was last tested (I keep the master product and was still getting different results due to setup). I now use an "Audit" board where I bundle the cables (30-40cm) in a particular "figure of 8" fashion via fixed wooden pegs. Thru' time I have convinced myself that this not only gives me worst case emissions but also that much sought after REPEATABILITY! I believe the setup is as per EN55022. I have a photograph* of this Audit board to allow this forum to comment on the good and the bad points of using such a system. Also, is there any reason I cannot take this Audit board to a Test House for Product Compliance testing and at the same time get correlation between a Compliance site and my own site? Photograph details (EUT with 3 X Serial Ports, PSTN and DC SELV power connection) 1. The 1M, 2M and 3M indicate the Horizontal bundling of cables from RS232 ports which would go to a tabletop EUT peripheral (or leave open circuit). The 3 lengths are connected to similar ports. This covers the different lengths issues. 2. The P is the inline power supply O/P cable going to the EUT. This is bundled vertically as it represents the power supply sitting on a customers floor. 3. The T is the PSTN telecomms cable. Again bundled vertically as it represents the cable going from the EUT to the wall socket. Finally, I have never understood the EN55022 figure 10 note 1 "If cables which hang closer than 40cm to the horizontal ground plane cannot be shortened to appropriate length, the excess shall be folded back and forth forming a bundle 30cm to 40cm long". Does this mean you can cut the cable to 1m or ? even though you will be shipping say 2m cables with the product? *I have not attached the photograph, 212Kb. This will be sent to those requesting it i.e. to those people who are thinking of commenting on this email. I look forward with interest to this forums comments. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.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: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.co
RE: Radiated Emissions setup
A few loose comments and additions on your approach: The CISPR committee is like you seeking for repeatability in test set ups. Therefore an effort is made to create a common set up for immunity and emission test set up. The idea is a (vert) cylindric volume of 1m60 miniumum diameter for left and right cables to extend 80 cm and then leading 80 cm down to ground surface where each cable is clamped using an (yet) undefined ferrite clamp. (on rotating table) Several propositions are into the voting chain of which one is an amendment to CISPR 16-1. The 1m60 cylinder does not cope for EUT sizes, so in order to create a workable test setup 2 m cylinder is required and still allow for moderate EUT sizes. In addition to the 2 m cylinder a 1m distance to the walls of the FAR would be required, and sufficient distance is required to the antenna for it to "illuminate" the full cylinder. Calibration procedures are also in the propositions. However, a full compliant set up cannot be made in a 3 m room, due to size restrictions. Several aspects may however lead to substantial different radiations results as before: The fixed radiating lead length of 2 x 80 cm + ferrite behaving as 150 Ohms Common Mode load) makes the lead look like infinite to the EUT disturbanc voltage source (at least that's the idea). For frequencies below 1/2 lambda lead lenght ( 1m60 = 92 Mhz the wires (left + rigth) begin to behave like a shortened dipole with (of course) reduced emssions compared to real life where cables CAN be infinite. The procedure is now to find out in what combination of left right cable lay out creates maximum emissions. If you forget that, different phase steered cables may compensate emissions. Think of the cables as being current fed from a matrix of interference sources with arbitrary voltage where each cable is connected to a different point of the matrix and you get the idea. Just putting cables where you like is *not* sufficient. A FAR differs from an OATS in that no height variation of the antenna is required. For small sources or line radiating sources such as a dipole cable set (!!), the low frequency results may be up to 24 dB higher then at the OATS (with HOR polarization) this is due to the fact that on an OATS the reflected ground wave is in opposite phase and attenuates the incident wave. For this to compensate the hight variations were invented. travelling ways differ when rising and lowering the antenna until a maximum was found. Unfortunately at low frequencies one will never never rise the antenna as high as required for a full compensation of this effect. (I have a Mathcad 2001 model for those who want to experiment: infinite height would be required but signal topsat 15m). As there is no ground reflection in the FAR, the low frequency response is much better then on the OATS. Though antenna signal is 5 dB (theoretic 6) lower in a FAR because the absence of the reflected wave the effect of the insufficient OATS model are not accounted for. At vertical polarization this OATS effect does not happen as the reflected wave is not in opposite phase to the incident wave. Larger or 3D EUTS do behave better due to more variations of way length between radiator and antenna, and large receiving antennas have less problems then dipoles (especially active dipoles : small !!)./ Just a few notes to explain for the many differences that may happen between set up variations. Gert Gremmen -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil Sent: dinsdag 20 augustus 2002 18:00 To: 'emc-p...@majordomo.ieee.org' Subject: Radiated Emissions setup Hi Forum, As we all know test setups are absolutely critical to EMC results. I have the good fortune of having a good pre-compliance radiated emissions site (3m OATS, Fully or Semi Anechoic Chamber). From using this site I see all sorts of "funnies" but still the most annoying is how much you can change the emission results just by changing cable positions. I carry out regular EMC audits and could never quite get the same results as 6 months previous, when that particular product was last tested (I keep the master product and was still getting different results due to setup). I now use an "Audit" board where I bundle the cables (30-40cm) in a particular "figure of 8" fashion via fixed wooden pegs. Thru' time I have convinced myself that this not only gives me worst case emissions but also that much sought after REPEATABILITY! I believe the setup is as per EN55022. I have a photograph* of this Audit board to allow this forum to comment on the good and the bad points of using such a system. Also, is there any reason I cannot take this Audit board to a Test House for Product Compliance testing and at the same time get correlation between a Compliance site and my own site? Photograph details (EUT with 3 X Serial Ports, PSTN and DC SELV power connection) 1. The 1M, 2M and 3M in
RE: Radiated Emissions setup
Only one comment: If you take this peg board to an OATS how can they maximize the cables? -Original Message- From: Alex McNeil [mailto:alex.mcn...@ingenicofortronic.com] Sent: Tuesday, August 20, 2002 10:00 AM To: 'emc-p...@majordomo.ieee.org' Subject: Radiated Emissions setup Hi Forum, As we all know test setups are absolutely critical to EMC results. I have the good fortune of having a good pre-compliance radiated emissions site (3m OATS, Fully or Semi Anechoic Chamber). From using this site I see all sorts of "funnies" but still the most annoying is how much you can change the emission results just by changing cable positions. I carry out regular EMC audits and could never quite get the same results as 6 months previous, when that particular product was last tested (I keep the master product and was still getting different results due to setup). I now use an "Audit" board where I bundle the cables (30-40cm) in a particular "figure of 8" fashion via fixed wooden pegs. Thru' time I have convinced myself that this not only gives me worst case emissions but also that much sought after REPEATABILITY! I believe the setup is as per EN55022. I have a photograph* of this Audit board to allow this forum to comment on the good and the bad points of using such a system. Also, is there any reason I cannot take this Audit board to a Test House for Product Compliance testing and at the same time get correlation between a Compliance site and my own site? Photograph details (EUT with 3 X Serial Ports, PSTN and DC SELV power connection) 1. The 1M, 2M and 3M indicate the Horizontal bundling of cables from RS232 ports which would go to a tabletop EUT peripheral (or leave open circuit). The 3 lengths are connected to similar ports. This covers the different lengths issues. 2. The P is the inline power supply O/P cable going to the EUT. This is bundled vertically as it represents the power supply sitting on a customers floor. 3. The T is the PSTN telecomms cable. Again bundled vertically as it represents the cable going from the EUT to the wall socket. Finally, I have never understood the EN55022 figure 10 note 1 "If cables which hang closer than 40cm to the horizontal ground plane cannot be shortened to appropriate length, the excess shall be folded back and forth forming a bundle 30cm to 40cm long". Does this mean you can cut the cable to 1m or ? even though you will be shipping say 2m cables with the product? *I have not attached the photograph, 212Kb. This will be sent to those requesting it i.e. to those people who are thinking of commenting on this email. I look forward with interest to this forums comments. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.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: 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: Radiated Emissions setup
Neil, I would like to see the pictures of your audit board. Without seeing the pictures I have the following comments. 1. I think this is a very good idea from a repeatability standpoint and I would like to consider adopting it. 2. It may be more trouble than simply draping the cables over the table edge, but less than bundling them properly. 3. Some of our customers bring their products in already attached to such a board with their cables all fastened securely in configurations accepted by their customers. This also lessens the setup time and gets them in and out quicker. 4. I believe that Note 1 of Figure 10 in EN 55022 refers to cables which connect one piece of gear on the table to another. If the cables were cut, it would require splicing or installing connectors. If a shorter cable were used, it may not represent actual use. I feel that generally customers having a two meter cable which is longer than needed would either drape it to the floor (which is not normally a metal ground plane), or bundle it neatly to keep it out of the way. On the other hand, since we as testers never know how equipment will be configured, the demand for repeatability requires that a system such as that described in Figure 10 be used. Robert Seay -Original Message- From: Alex McNeil [mailto:alex.mcn...@ingenicofortronic.com] Sent: Tuesday, August 20, 2002 12:00 PM To: 'emc-p...@majordomo.ieee.org' Subject:Radiated Emissions setup Hi Forum, As we all know test setups are absolutely critical to EMC results. I have the good fortune of having a good pre-compliance radiated emissions site (3m OATS, Fully or Semi Anechoic Chamber). From using this site I see all sorts of "funnies" but still the most annoying is how much you can change the emission results just by changing cable positions. I carry out regular EMC audits and could never quite get the same results as 6 months previous, when that particular product was last tested (I keep the master product and was still getting different results due to setup). I now use an "Audit" board where I bundle the cables (30-40cm) in a particular "figure of 8" fashion via fixed wooden pegs. Thru' time I have convinced myself that this not only gives me worst case emissions but also that much sought after REPEATABILITY! I believe the setup is as per EN55022. I have a photograph* of this Audit board to allow this forum to comment on the good and the bad points of using such a system. Also, is there any reason I cannot take this Audit board to a Test House for Product Compliance testing and at the same time get correlation between a Compliance site and my own site? Photograph details (EUT with 3 X Serial Ports, PSTN and DC SELV power connection) 1. The 1M, 2M and 3M indicate the Horizontal bundling of cables from RS232 ports which would go to a tabletop EUT peripheral (or leave open circuit). The 3 lengths are connected to similar ports. This covers the different lengths issues. 2. The P is the inline power supply O/P cable going to the EUT. This is bundled vertically as it represents the power supply sitting on a customers floor. 3. The T is the PSTN telecomms cable. Again bundled vertically as it represents the cable going from the EUT to the wall socket. Finally, I have never understood the EN55022 figure 10 note 1 "If cables which hang closer than 40cm to the horizontal ground plane cannot be shortened to appropriate length, the excess shall be folded back and forth forming a bundle 30cm to 40cm long". Does this mean you can cut the cable to 1m or ? even though you will be shipping say 2m cables with the product? *I have not attached the photograph, 212Kb. This will be sent to those requesting it i.e. to those people who are thinking of commenting on this email. I look forward with interest to this forums comments. Kind Regards Alex McNeil Principal Engineer Tel: +44 (0)131 479 8375 Fax: +44 (0)131 479 8321 email: alex.mcn...@ingenicofortronic.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: 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 subscri
