Readability
SolaR load The energy of the radiation that is generated by the sun on a surface—which we call “Solar Loading” and is measured in watts per square meter—can far outweigh the effect that ambient temperature alone would cause. For example, a display that is outdoors in the shade with the ambient temperature at a comfortable 60°F would see an increase in the internal temperatures
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Temperature and Solar Irradiance in Las Vegas on June 28, 2012: A combination of high temps (+40°C) and high solar load (900 W/m2) from 2-4pm makes for a very harsh environment if a digital display is facing west towards the setting sun without any cover. of the display by over three times. This temperature increase would impact the life and operation of all the internal display components. Dealing with the temperature and this solar load relies on the thermal management system that the display uses.
SolutionS “Display in a Box.” One solution that can be utilized to deal with extreme
Condensation inside a display enclosure. signshop.com
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A typical display operates with a maximum brightness level around 250 to 350 “nits” or candelas per square meter (cd/ m2). When exposed directly to high ambient light however, such a display can become almost unreadable. The light and especially the reflections cause a decrease in contrast, which becomes worse as the ambient light increases. Most displays designed for high-bright environments typically compensate for this by increasing the output of the LED backlights, which drives more light to the display. However this can end up causing a more washed out image, lacking in contrast. In fact, we find that improving contrast is more important than brightness on an outdoor display. A typical outdoor display might have a maximum brightness of 1000 to 2500 nits. But a display that uses optical bonding with an anti-reflective panel directly to the LCD can reduce internal reflections, driving up the contrast of the image and therefore requiring less “light output” to create a vivid and readable image.
temperatures or conditions would be to simply put the displays in an enclosure that would allow a “standard” digital sign to function within operating specifications. Such an enclosure could be air-conditioned or heated, and it could also be sealed to prevent some amount of water ingress. The biggest advantage of this solution is that such enclosures are “display agnostic.” You could use any display inside these enclosures and could replace those displays independent of the enclosure. However the disadvantages can be significant: (1.) You are relying on an external mechanical system (the air conditioner) to operate, in order to keep the display environment within its specifications so that it can remain functioning. These systems can also be loud and unusable in certain applications (such as in a drive-through). (2.) Such artificial environments create a host of other issues that can decrease the overall performance of the display— the first of which is managing the condensation inside the enclosure when the solar radiation and the ambient temperatures go in opposite directions. Having displays enclosed behind a
January 2014 // Sign Builder Illustrated
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