Monday, 28 March 2011

Electromagnetic radiation from CRT, LCD plasma and LED screens and TVs


CRT - TV and screen based on a Cathode-Ray Tube.

There is a wide variety of television in today market and households.  Televisions and screens that are based on Cathode-ray Tube (CRT), the big, clumsy round and heavy devices, are the oldest type of TVs and they emit the highest levels of electromagnetic radiation (compared to other types of TVs and to other radiation sources in the house). The reason is that these TVs work on the principle of a variable electromagnetic field generated around the screen used to change the projection of the electrons making their way from the electronic booster/canon on the back of the tube to the Fluorescent screen. This field surrounds the screen on all sides. At the front of an old CRT screen there is a protective layer that blocks some of the radiation. Therefore on the back and sides (where there is no protection) the radiation levels are the highest. Since the low frequency electromagnetic radiation can pass through walls, a common mistake is to place a bed next to the other side of that wall where a CRT-TV is placed at. In a CRT TV some levels of electromagnetic radiation will be emitted even on standby mode.

In order to save office space, many businesses and offices, place computer tables against each other, back to back, which means that also the computer screens are placed back to back. In this situation, workers are exposed to high levels of electromagnetic radiation from the rear  and sides of the CRT screens.
Safety distance from a 29" CRT TVs is at least 2 meters from all sides. A safety distance from a 19" CRT PC screen should be around half a meter in any direction.

 CRT TVElectromagnetic radiation from 29" CRT TV

 
Electromagnetic radiation from 14" CRT TV 


LED/LCD and Plasma TVs

LCD, plasma and LED screens and televisions work in a digital method and are not based on a magnetic principle. Therefore the radiation levels that are emitted from all sides, are very low compared to a CRT TV or screen. The sources of radiation in these monitors are computerized circuits, microprocessors and power supplies that are located on the electronic circuit board on the back on the screen. Since the radiation levels from LCD/LED and plasma screens are usually very low, the safety distance from LCD/LED and plasma screens is only half a meter.

Plasma screens and TV are also a source of electric pollution (it produces an electrical noise that is added on to the electrical grid at home) but the levels of low frequency electromagnetic radiation emitted from the plasma screens are similar to the levels emitted from LCD and LED screens.
Safety distance from LCD screens, plasma TV LED is half a meter in any direction

Electromagnetic radiation from 19" LCD TV 40" LCD TV

2 comments:

  1. it is interesting that,, latest led and lcd displays are more safer

    ReplyDelete