RE: radiated emission from 15 inch TFT-LCD

2002-02-08 Thread Garnier, David S (MED)

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 | 




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RE: radiated emission from 15 inch TFT-LCD

2002-02-08 Thread XU,CATHERINE (HP-SanDiego,ex1)

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 | 




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Re: radiated emission from 15 inch TFT-LCD

2002-02-07 Thread Chris Maxwell

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 | 




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Re: radiated emission from 15 inch TFT-LCD

2002-02-07 Thread John Woodgate

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!

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Re: radiated emission from 15 inch TFT-LCD

2002-02-07 Thread reheller


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

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radiated emission from 15 inch TFT-LCD

2002-02-07 Thread 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

---
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