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Date:	Tue, 22 Jan 2002 00:24:59 PST7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Monitor Glitch

Content Type: text/plain

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Benedict G. Archer wrote:
>
> Incandescent light bulb life is a function of time
> on and operating temperature. Lifetime measured
> in time on is the same whether on continuously
> or cycled on/off at ~1 Hz or any slower rate.

Ben, I'm curious about the study you're referring to. The studies I've
read (although I can't cite any of them) and my personal experience both
indicate that incandescent bulbs are most likely to fail at power-on.
The studies said it was because of thermal shock.

For example, I've changed the 75w bulb in my desk lamp several times --
and each time the failure has been when I turned it on. A lamp has
never suddenly "gone out" while I'm using it. (I have had incandescent
lamps do that, but rarely.)

I'm always willing to learn. Can you point me at a study that shows
these lamps aren't more likely to fail at power-on?

(Tangent: I extended the life of the incandescent equipment lamps (such
as vu meter lamps) in the studios by running them at low voltage,
typically 10%-20% lower than their "spec" voltage. Neumann record
cutting lathes dropped the voltage even more -- iirc they ran 12v lamps
at 9v which is a 25% drop. Architectural lighting is sometimes run at a
lower voltage to reduce the maintenance cost of constant relamping.
Theme park special effect lighting is sometimes run at a lowered voltage
for the same reason. I've seen manufacturer charts on lamp life vs.
voltage applied as a % of spec voltage and the change is both non-linear
and quite dramatic.)

(Another tangent: The rated life expectancy hours are printed on the
box that the 120v incandescent lamp comes in. (Low voltage incandescent
lamps also have life expectancies.) I've seen 650 hours to 1300 hour
life expectancies for 60w-100w bulbs; the cheaper bulbs usually have
lower life expectancies. Not a big cost factor since most of the cost
of operating the bulb is the electricity consumed. 1000 hours at 100w
is 100kw-hr, and at 16 cents/kw-hr that's $16 for the electricity -- and
only $1 for the bulb.)

- Peter

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