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Why do Digital Displays have a Screen saver. When CRT's Don't?
0culus:
HP 85662A spectrum analyzer display (8566A/B, 856(7/8A)/B) is another one I forgot about...shift+g to turn off beam and shift+h to turn it on again. Can also be programmed via GPIB.
jklasdf:
The Agilent 54622d oscilloscope has a screensaver for its CRT (although it's easier to implement there since it's a digital scope). I think if high-end analog oscilloscopes had continued to be developed into the late 90s, screensavers for the CRT might have become a thing, but for just a plain old analog oscilloscope it seems like a lot of work to implement. The only ones I can think of (as already mentioned) are the Teks with MCP.
I don't think I've ever seen a screensaver on a modern LCD oscilloscope, or if they have one it can at least be disabled. Some early CRT DSOs (e.g. monochrome LeCroys) often have pretty noticeable screen burn-in, and really could've used a screensaver back in the day.
I've seen some screensavers on LCD TVs when there is no signal, or from DVD players when there's no disc, but otherwise I think they're fairly uncommon on most of the devices I've seen. It kind of makes sense when otherwise it would just display a static error message, but I think screen savers are there mostly for legacy reasons or to look nice nowadays, rather than to prevent screen burn-in.
0culus:
I know for a fact that Keysight MSO series scopes have screensavers. It's buried in some settings menu, and by default just blanks the screen and moves the Keysight branding around.
vk6zgo:
With normal TV receivers & picture monitors, the normal cause of "burn in" could be caused by still images like test patterns, or more often, text, bright white lines on a dark background, large white geometric shapes, etc.
The most common cause in TV Broadcasting, however, was deliberate underscan.
Older TV tubes had pronounced rounded corners, so if they needed to display a correct 3:4 image, it was common to set the scans to "underscan" to achieve this (it was often provided as a switch function)
If, after being set in this manner for a long time, it was restored to "full scan", the burnt on image of the smaller raster would be evident as a sharply delineated area of lower brightness.
Until the 1980s, the default with no video input was for the TV/monitor horizontal & vertical scans to "free run" at close to the normal scan rates, & the display to remain visible, basically showing random noise instead of video.
If the scans were set to "underscan", it could still cause burn in.
Starting in that decade, TV sets were designed to display a black screen when video was lost.
Picture monitors did not, by default, do this.
When CRT based monitors were used with computers, the usual display was a black screen with white (or green) text displayed upon it.
As some text was common to many operations, the problem arose of that text burning in.
The computer would automatically generate the "screen saver" when "in standby", but not currently busy.
flolic:
My current laptop (HP ZBook 15 G1) with FHD IPS panel has very noticeable image retention after few hours displaying the same image. It gradually goes away, but previous image is still noticeable after an hour.
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