RE: radiated emission from 15 inch TFT-LCD
Hi, The Hitachi Europe website has a app note on flat panel displays called APPS/043/1.0, titled "flat panel displays - emi considerations." I have a copy on my hard drive that I would be willing to send. dave garnier -Original Message- From: XU,CATHERINE (HP-SanDiego,ex1) [mailto:x...@hp.com] Sent: Thursday, February 07, 2002 6:27 PM To: EMC-PSTC Internet Forum Subject: RE: radiated emission from 15 inch TFT-LCD Hi, The following paper might be a good references on this topic: EMC analysis of an 18" LCD monitor Zeeff, T.M.; Hubing, T.H.; Drewniak, J.L.; Dussroff, R.E.; Van Doren, T.P. Electromagnetic Compatibility, 2000. IEEE International Symposium on , Volume: 1 , 2000 Page(s): 169 -173 vol.1 Catherine Xu ---| EMC Engineer | Hardware Test & Regulations| All-in-One Personal Printing - HP | -Original Message- From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, February 07, 2002 2:02 PM To: EMC-PSTC Internet Forum Subject: Re: radiated emission from 15 inch TFT-LCD Importance: High Hi, It has been my (limited) experience that the LCD itself isn't much trouble for emissions. However, typically the LCD is in the face of the product and there may be some high speed, processor type circuits behind it. We have run into trouble with the processor emissions leaking around the LCD. Most of the LCD's that I have experience with have a metal plate on the back of them. This plate is usually a fairly good shield. So, emissions don't go through the LCD. However, if this plate isn't bonded well to the metal chassis at its edges (either with gasketing or with straps placed every 1/2" or so), then emissions will leak around the LCD. I'm wondering what type of "shielded" window you have. If it is an ITO (Indium Tin Oxide) coating, it is conductive enough to dissipate static; but not very good for emissions. We have tried them before only to remove them (because they hurt visibility) and concentrate instead on sealing around the LCD as mentioned above with better results. However, if you have a metal mesh shielded window, that should be good enough to contain any emissions; but again, check how it is sealed around the edges. I still think that even in this case, it would be worth a try to get rid of the shielding window and concentrate on bonding the metal backplate of the LCD to your product chassis. In a pinch at the lab, we've done it with copper tape with decent results. Another thing to look at is the power and signal interface cables to the LCD. They may be carrying processor noise up to your LCD. We typically filter them with some very light capacitance ( 10's of pF or so). Just enough to let the video signals through while bleeding off some of that nasty processor noise. We have also tried clamp on ferrites on these cables. Best of luck my man. Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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...@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://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...@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://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 lis
RE: radiated emission from 15 inch TFT-LCD
Hi, The following paper might be a good references on this topic: EMC analysis of an 18" LCD monitor Zeeff, T.M.; Hubing, T.H.; Drewniak, J.L.; Dussroff, R.E.; Van Doren, T.P. Electromagnetic Compatibility, 2000. IEEE International Symposium on , Volume: 1 , 2000 Page(s): 169 -173 vol.1 Catherine Xu ---| EMC Engineer | Hardware Test & Regulations| All-in-One Personal Printing - HP | -Original Message- From: Chris Maxwell [mailto:chris.maxw...@nettest.com] Sent: Thursday, February 07, 2002 2:02 PM To: EMC-PSTC Internet Forum Subject: Re: radiated emission from 15 inch TFT-LCD Importance: High Hi, It has been my (limited) experience that the LCD itself isn't much trouble for emissions. However, typically the LCD is in the face of the product and there may be some high speed, processor type circuits behind it. We have run into trouble with the processor emissions leaking around the LCD. Most of the LCD's that I have experience with have a metal plate on the back of them. This plate is usually a fairly good shield. So, emissions don't go through the LCD. However, if this plate isn't bonded well to the metal chassis at its edges (either with gasketing or with straps placed every 1/2" or so), then emissions will leak around the LCD. I'm wondering what type of "shielded" window you have. If it is an ITO (Indium Tin Oxide) coating, it is conductive enough to dissipate static; but not very good for emissions. We have tried them before only to remove them (because they hurt visibility) and concentrate instead on sealing around the LCD as mentioned above with better results. However, if you have a metal mesh shielded window, that should be good enough to contain any emissions; but again, check how it is sealed around the edges. I still think that even in this case, it would be worth a try to get rid of the shielding window and concentrate on bonding the metal backplate of the LCD to your product chassis. In a pinch at the lab, we've done it with copper tape with decent results. Another thing to look at is the power and signal interface cables to the LCD. They may be carrying processor noise up to your LCD. We typically filter them with some very light capacitance ( 10's of pF or so). Just enough to let the video signals through while bleeding off some of that nasty processor noise. We have also tried clamp on ferrites on these cables. Best of luck my man. Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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...@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://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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: radiated emission from 15 inch TFT-LCD
Hi, It has been my (limited) experience that the LCD itself isn't much trouble for emissions. However, typically the LCD is in the face of the product and there may be some high speed, processor type circuits behind it. We have run into trouble with the processor emissions leaking around the LCD. Most of the LCD's that I have experience with have a metal plate on the back of them. This plate is usually a fairly good shield. So, emissions don't go through the LCD. However, if this plate isn't bonded well to the metal chassis at its edges (either with gasketing or with straps placed every 1/2" or so), then emissions will leak around the LCD. I'm wondering what type of "shielded" window you have. If it is an ITO (Indium Tin Oxide) coating, it is conductive enough to dissipate static; but not very good for emissions. We have tried them before only to remove them (because they hurt visibility) and concentrate instead on sealing around the LCD as mentioned above with better results. However, if you have a metal mesh shielded window, that should be good enough to contain any emissions; but again, check how it is sealed around the edges. I still think that even in this case, it would be worth a try to get rid of the shielding window and concentrate on bonding the metal backplate of the LCD to your product chassis. In a pinch at the lab, we've done it with copper tape with decent results. Another thing to look at is the power and signal interface cables to the LCD. They may be carrying processor noise up to your LCD. We typically filter them with some very light capacitance ( 10's of pF or so). Just enough to let the video signals through while bleeding off some of that nasty processor noise. We have also tried clamp on ferrites on these cables. Best of luck my man. Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | --- 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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: radiated emission from 15 inch TFT-LCD
I read in !emc-pstc that rehel...@mmm.com wrote (in ) about 'radiated emission from 15 inch TFT-LCD', on Thu, 7 Feb 2002: >It has been my experience that LCDs do not emit much energy in themselves >but their >driving electronics might. I just tested a thin film transistor liquid >crystal display on Tuesday. It's nice to know that theory works sometimes in EMC. An LCD has a strictly-confined electric field of very small dimensions and not very much current flows. So one might well expect only minimal emission. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. 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: davehe...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: radiated emission from 15 inch TFT-LCD
It has been my experience that LCDs do not emit much energy in themselves but their driving electronics might. I just tested a thin film transistor liquid crystal display on Tuesday. Bob Heller 3M Product Safety, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 = "Wani, Vijay (V)" To: "'emc-p...@majordomo.ieee.org'" cc: (bcc: Robert E. Heller/US-Corporate/3M/US) Subject: radiated emission from 15 inch TFT-LCD 02/06/2002 09:01 PM Please respond to "Wani, Vijay (V)" hello Group: My question is kind of general but i would appreciate any input / experience. typical, TFT-LCD is enclosed in a metal enclosure and there is a shielded window to prevent any emi from front. Is LCD (video signal) big source of emi? if LCD unit not properly isolated (shielded) within a system, does it immune to emi (intra-system interference)? thank you in advance. vijay --- 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...@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://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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
radiated emission from 15 inch TFT-LCD
hello Group: My question is kind of general but i would appreciate any input / experience. typical, TFT-LCD is enclosed in a metal enclosure and there is a shielded window to prevent any emi from front. Is LCD (video signal) big source of emi? if LCD unit not properly isolated (shielded) within a system, does it immune to emi (intra-system interference)? thank you in advance. vijay --- 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...@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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"