Re: Low Frequency Conducted Immunity....
Scott, Being a low frequency problem, it sounds like a likely candidate for a common impedance coupling. Possibily through a common ground return. Mind you, if it is Low freq in nature, series inductance [even large amounts ~ 3 mH ect...] and common-mode chokes may not work. Try checking the grounding. The design should be such that no currents flows in any part of the metal work, (which is a rather tall order for an automotive part). :-) Tim Foo scott@jci.com Sent by: To: emc-p...@majordomo.ieee.org owner-emc-pstc@majordomcc: (bcc: Wan Juang Foo/ece/staff/npnet) o.ieee.org Subject: Low Frequency Conducted Immunity 11/02/01 09:04 PM Please respond to Scott.Mee Thank you to all who have responded to my LFC immunity issue. Your help is much appreciated. Regards, Scott Mee EMC Engineer Johnson Controls Inc. PH: 616.394.2565 EMAIL: scott@jci.com +++ Cortland Richmond 72146@compuserve.com Sent by: owner-emc-p...@majordomo.ieee.org 10/31/01 12:50 AM Please respond to Cortland Richmond I'd be inclined to look at the design. Bandaids have a way of multiplying until your product looks like a mummy. If it's a low-level power problem, make sure the EUT's regulator can respond to induced ripple. This may be as simple as exchanging a cheap electrolytic cap for one with better ESR, or you may have to redesign the regulator's filter loop. If the problem is unregulated power to a PA stage, try getting better balance in the stage; look at it as a CMR problem. Look for ground-loop problems; a shared return between a stage run from the injection point and a low-level amplifier will do what you report. And you might look for an unintended path. Active switches can be modulated, too. Good luck! Cortland Ken Javor ken.ja...@emccompliance.com Sent by: owner-emc-p...@majordomo.ieee.org 10/30/01 02:54 AM Please respond to Ken Javor More info needed on type of power supply or whether unit simply runs off 12 Vdc. A power converter will definitely do the trick, but obviously is not a solution unless it is already part of the EUT. -- scott@jci.com Sent by: owner-emc-p...@majordomo.ieee.org 10/30/01 12:42 AM Please respond to Scott.Mee Hello Group, I am working with and electronic device which contains and audio output. During a low frequency conducted immunity test, a tone can be heard at the output of the audio section with a frequency equal to that of the test frequency. The test starts at the lower end of the audio spectrum [~400Hz] and progresses over time up to the top end of the audio spectrum [~30kHz]. I would like to be able to filter the conducted noise from getting into my electronic device. This is an automotive application, so if I am unsuccessful alternator noise may also be heard in my audio signal during normal operation in the vehicle. I have tried a few things to reduce the amount of noise such as: 1. LC filter with a cutoff at 1kHz 2. Series inductance [large amounts ~ 3mH] 3. Various common mode choke types, each with different core materials [ie. iron core, ferrite core, etc] #1 helped some, but is not effective enough, #2 was very successful, but the size of the choke would be enormous and not practical in this application, #3 was not effective Can anyone suggest an improvement upon the three methods above, or suggest something different? I would like to implement something on the board itself if possible, but modification to the harness may
Low Frequency Conducted Immunity....
Thank you to all who have responded to my LFC immunity issue. Your help is much appreciated. Regards, Scott Mee EMC Engineer Johnson Controls Inc. PH: 616.394.2565 EMAIL: scott@jci.com +++ Hello Group, I am working with and electronic device which contains and audio output. During a low frequency conducted immunity test, a tone can be heard at the output of the audio section with a frequency equal to that of the test frequency. The test starts at the lower end of the audio spectrum [~400Hz] and progresses over time up to the top end of the audio spectrum [~30kHz]. I would like to be able to filter the conducted noise from getting into my electronic device. This is an automotive application, so if I am unsuccessful alternator noise may also be heard in my audio signal during normal operation in the vehicle. I have tried a few things to reduce the amount of noise such as: 1. LC filter with a cutoff at 1kHz 2. Series inductance [large amounts ~ 3mH] 3. Various common mode choke types, each with different core materials [ie. iron core, ferrite core, etc] #1 helped some, but is not effective enough, #2 was very successful, but the size of the choke would be enormous and not practical in this application, #3 was not effective Can anyone suggest an improvement upon the three methods above, or suggest something different? I would like to implement something on the board itself if possible, but modification to the harness may be possible if necessary. Thank you in advance for any help! Regards, Scott Mee EMC Engineer Johnson Controls Inc. PH: 616.394.2565 EMAIL: scott@jci.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: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Low Frequency Conducted Immunity....
I'd be inclined to look at the design. Bandaids have a way of multiplying until your product looks like a mummy. If it's a low-level power problem, make sure the EUT's regulator can respond to induced ripple. This may be as simple as exchanging a cheap electrolytic cap for one with better ESR, or you may have to redesign the regulator's filter loop. If the problem is unregulated power to a PA stage, try getting better balance in the stage; look at it as a CMR problem. Look for ground-loop problems; a shared return between a stage run from the injection point and a low-level amplifier will do what you report. And you might look for an unintended path. Active switches can be modulated, too. Good luck! 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: 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Re: Low Frequency Conducted Immunity....
More info needed on type of power supply or whether unit simply runs off 12 Vdc. A power converter will definitely do the trick, but obviously is not a solution unless it is already part of the EUT. -- From: scott@jci.com To: emc-p...@majordomo.ieee.org Subject: Low Frequency Conducted Immunity Date: Mon, Oct 29, 2001, 10:42 AM Hello Group, I am working with and electronic device which contains and audio output. During a low frequency conducted immunity test, a tone can be heard at the output of the audio section with a frequency equal to that of the test frequency. The test starts at the lower end of the audio spectrum [~400Hz] and progresses over time up to the top end of the audio spectrum [~30kHz]. I would like to be able to filter the conducted noise from getting into my electronic device. This is an automotive application, so if I am unsuccessful alternator noise may also be heard in my audio signal during normal operation in the vehicle. I have tried a few things to reduce the amount of noise such as: 1. LC filter with a cutoff at 1kHz 2. Series inductance [large amounts ~ 3mH] 3. Various common mode choke types, each with different core materials [ie. iron core, ferrite core, etc] #1 helped some, but is not effective enough, #2 was very successful, but the size of the choke would be enormous and not practical in this application, #3 was not effective Can anyone suggest an improvement upon the three methods above, or suggest something different? I would like to implement something on the board itself if possible, but modification to the harness may be possible if necessary. Thank you in advance for any help! Regards, Scott Mee EMC Engineer Johnson Controls Inc. PH: 616.394.2565 EMAIL: scott@jci.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: No longer online until our new server is brought online and the old messages are imported into the new server. --- 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: No longer online until our new server is brought online and the old messages are imported into the new server.
Low Frequency Conducted Immunity....
Hello Group, I am working with and electronic device which contains and audio output. During a low frequency conducted immunity test, a tone can be heard at the output of the audio section with a frequency equal to that of the test frequency. The test starts at the lower end of the audio spectrum [~400Hz] and progresses over time up to the top end of the audio spectrum [~30kHz]. I would like to be able to filter the conducted noise from getting into my electronic device. This is an automotive application, so if I am unsuccessful alternator noise may also be heard in my audio signal during normal operation in the vehicle. I have tried a few things to reduce the amount of noise such as: 1. LC filter with a cutoff at 1kHz 2. Series inductance [large amounts ~ 3mH] 3. Various common mode choke types, each with different core materials [ie. iron core, ferrite core, etc] #1 helped some, but is not effective enough, #2 was very successful, but the size of the choke would be enormous and not practical in this application, #3 was not effective Can anyone suggest an improvement upon the three methods above, or suggest something different? I would like to implement something on the board itself if possible, but modification to the harness may be possible if necessary. Thank you in advance for any help! Regards, Scott Mee EMC Engineer Johnson Controls Inc. PH: 616.394.2565 EMAIL: scott@jci.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: No longer online until our new server is brought online and the old messages are imported into the new server.
