Xref: utzoo sci.electronics:11150 misc.consumers.house:10756
Path: utzoo!attcan!uunet!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics,misc.consumers.house
Subject: Re: florescents don't like cold!
Summary: Mercury vapor pressure
Message-ID: <3701@kitty.UUCP>
Date: 7 Apr 90 04:46:13 GMT
References: <29716@amdcad.AMD.COM> <14870@cbnewsc.ATT.COM> <28616@cup.portal.com>
Organization: Recognition Research Corp., Clarence, NY
Lines: 34

In article <28616@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes:
> I've been told that the reason for this phenomenon is that the mercury
> condenses in the tube.  If this is true, then it certainly makes sense
> that all tubes -- expensive or cheap -- made for normal household use
> would suffer from the phenomenon.

	This is correct.  The mercury in a fluroescent lamp will always
condense at the coldest point, reducing overall mercury vapor pressure,
thereby reducing light output.
 
	To a lesser extent cold temperatures have an effect upon the
phosphor and inert gas vapor pressure, which not only reduces light
output, but creates color shifts and requires longer starting time.

> It's also reasonable to believe that tubes specifically designed for
> outdoor use would work fine.  Perhaps they have more mercury or lower
> pressure or some mechanism for the filaments to heat the mercury.

	Low temperature fluorescent lamps are generally filled with
argon at lower pressure, in addition to having a thicker or coated
glass wall for thermal insulation.

> Do all flourescent tubes have filaments? 

	No.

> What's the internal difference among 1 vs. 2 pin tubes?

	No filament, and filament, respectively.

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