Blanking screens, saving electricity....

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Newsgroups: comp.sys.hp.hardware,comp.terminals,telrad.system
Date: Sun, 02 Feb 97 15:10:46 GMT
Organization: PencilNet, Inc.
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From: david@pencilnet.com (David Ehrens)
Subject: Re: Q: Power usage of monitors?


We supply a fair number of terminals for various Unix multiuser
applications, and we have found that configuring terminals for screen
saver or "powersaver" mode is generally preferable to turning them off
and on--on a daily basis.  They simply seem to last longer when
avoiding the shock of powering on.

Wyse terminals, in particular, seem to benefit greatly from leaving
them on; they seem to burn out the most of the 5 or 6 brands we sell.

-- 
David Ehrens

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Date: 3 Feb 1997 00:45:14 GMT
Organization: Hewlett-Packard Fort Collins Site
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From: myers@fc.hp.com (Bob Myers)
Subject: Re: Q: Power usage of monitors?


TMX1001 Daniel Ginensky 3807 (daniel@tmx100.elex.co.il) wrote:
>
> A question for hardware techies and lovers of planet earth:
>
> How much energy is saved per hour by actually turning off the screen of
> a workstation, rather than leaving it on in sleep mode with the screen
> blacked out?  Is it worthwhile to turn them off for the weekend (about
> 65 hours), or even overnight (about 15 hours)?  Does turning these
> monitors off harm them in any way?

> We have a large number of HP X terminals (monitor model A1097C), HP
> workstations (monitor model A4331D), and  NCD X-terminals (which have
> one power switch for the computer and the monitor together).  The vast
> majority are on all the time.  I am trying to figure out if it is
> worthwhile to instigate a movement to let the computer monitors sleep at
> night.


Typical power-consumption numbers for CRT monitors are around 80-100
watts or so, so I'll let you figure out your savings from there.

But another reason for turning the monitor off at night is to save the
*monitor*.

The shortest-lived component in the display is the CRT itself, and it
is aging whenever the unit is powered up, no matter what you're
displaying on the screen.  (As long as the filament is hot and the
electron gun is under bias, the cathode is emitting... and aging.)

Screen savers do NOT improve this situation, and in fact those simple
ones which merely blank the screen can actually hasten the cathode's
aging somewhat.  The more sophisticated ones, which leave a small
moving image on the screen, prevent phosphor burn, but do nothing to
save the CRT cathode.

Taking advantage of monitor power-saving features MAY help prolong the
monitor's life, IF you leave the monitor in a mode where the CRT is
powered down (at the very least, the heater voltage reduced to the
point where the cathode is no longer active) when the system is unused
for an extended period, such as overnight.

If this can't be done, then simply turning off the monitor is better
than leaving it on, even if you're not concerned about the savings in
power.  Yes, there IS the problem of thermal shock when the power is
cycled--and here the power-saving functions may do better, by leaving
the heater a *little* warm--but at least in my opinion, you're better
off cycling the power once per day than you are running the tube 24 hours
but only using it 8.  It's a tradeoff, like everything else.  Me, I
turn mine off, on my way out the door...


Bob Myers                                   | myers@fc.hp.com
Senior Engineer, Displays                   | Note: The opinions presented here
Workstation Systems Division                | are not those of my employer.
Hewlett-Packard Co., Ft. Collins, CO        |
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