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From: frankb@hpsad.HP.COM (Frank Ball)
Newsgroups: sci.electronics
Subject: Re: Re: Converting a florescent hood
Message-ID: <1840020@hpsad.HP.COM>
Date: 13 Dec 89 03:55:31 GMT
References: <23152@gryphon.COM>
Organization: HP Signal Analysis Division - Rohnert Park, CA
Lines: 18

*From: richard@gryphon.COM (Richard Sexton)
*Subject: Re: Re: Converting a florescent hood
*Newsgroups: alt.aquaria,sci.electronics,misc.consumers
*In article <21670@adm.BRL.MIL> moss@brl.mil (Gary S. Moss (VLD/VMB) <moss>) writes:
*>Recently, I learned something regarding rapid-start ballasts and flourescent
*>fixtures; certain, if not all such ballasts, require that a strip of metal
*>grounded to the ballast be roughly within 1 inch of the bulb along its entire
*>length.  
*
*Does anyone know why ?

I would suspect it is for the starting circuit.  They use a high voltage 
spike to ionize the gas inside, the spike is applied between the pins
on the end of the tube and the ground strip.  This sounds very similair to 
the triggering of a xenon flash tube, which have a trigger electrode that
is connected to the outside of the glass tube.

Frank Ball          frankb@hpsad.HP.COM