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 [email protected] | 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] 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"
