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Flat Panel LCD monitors with transformer external to panel (NOT built in)

Posted on 2003-11-12
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Last Modified: 2013-11-06
Looking for LCD monitors that do NOT have the transformer built into the panel.

I'm hoping for a website that keeps track of these things, perhaps one devoted to products with low electromagnetic radiation. Putting the transformer in the panel increases the electromagnetic radiation (EMRs).

Vendors and manufacturers I've talked to have a hard time keeping track of this detail if it isn't listed in their published specs - it's hard to get this information. The transformer is typically a small heavy black "brick" on the power cord when it isn't built into the monitor panel itself.
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Question by:esc_toe_account
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8 Comments
 
LVL 69

Expert Comment

by:Callandor
ID: 9733403
I have a Planar 19" that has the "brick" in the power cord.
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LVL 12

Expert Comment

by:public
ID: 9735055
>Putting the transformer in the panel increases the electromagnetic radiation (EMRs).
Why do you say that?
They all use a switching supply which has to meet EMI specs internal or external mounting does not make much difference.
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Author Comment

by:esc_toe_account
ID: 9741563
I say that as a result of internal testing on two models that switched from having the brick in the cord to placing it in the panel. Measurable radiation (using a radiation meter) clearly shows where the transformer is, whether on the cord or in the panel. (When it isn't in the panel, the radiation isn't there.)
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Author Comment

by:esc_toe_account
ID: 9741592
Callandor - the problem is, we have models both ways.

Manufacturers change this feature, but don't always publish this fact. We only found out initially when newer models started arriving with the transformer in the panel. We also found (not surprisingly) that we couldn't specify which type when we ordered. We did try to find older stock (having vendors physically check their warehouse to see which type they had) but no luck.
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Expert Comment

by:public
ID: 9741975
>Measurable radiation (using a radiation meter) clearly shows where the transformer is
are you sure you know what you actually measure? radiation meter?? transformer ??
These tests are normally done with a spectrum analyzer.
The decision where to place the power supply is based on cost not on emissions strategy.
Compliance testing experience shows that most of the EMI is emitted by the flat panel matrix and not by the power supply.
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Accepted Solution

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Callandor earned 160 total points
ID: 9742010
If you're looking for low emission displays, search for keywords "MPR II" or "TCO" certification.  These are guidelines developed in Sweden by a number of organizations to set limits on electric and magnetic field emissions, and TCO-99 is the most recent one.  Philips, CTX, LG, and Iiyama are among the manufacturers who produce compliant hardware.  See http://www.hwupgrade.com/monitor/index5.html for details on the MPR and TCO specs.
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Author Comment

by:esc_toe_account
ID: 9743015
public - Electromagnetic radiation (EMR) meter. Don't know the technology it uses (rented). Don't care what the manufacturer's motives are, or what other testing seems to show. In-house testing shows there is an issue, hence this question.

In-house testing experience shows that removing the brick from the cord and placing its components in the panel changes the EMR measurements, registering noticeable EMR in a specific area of the monitor panel when the brick is in the panel, and measuring little or none in that area when the brick is on the cord.
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LVL 12

Expert Comment

by:public
ID: 9743326
>In-house testing experience shows that removing the brick from the cord and placing >its components in the panel changes the EMR measurements

Yes but unless you know what the EMR "meter" actually measures, you could be increasing user health risk, not decreasing it.
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