🚀 go-pugleaf

richard@gryphon.COM (Richard Sexton) writes:

>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 ?


Eureka! That's why half my fluoros don't start reliably!

This metalwork would affect the shape of the field when the starting-kick
is applied. The field strength (volts/inch) would be heightened by the ground
plane.

An isolated tube refuses to fire:

	[--------------------------------------]
	[                                      ]
	[--------------------------------------]
	|<-- voltage developed across here --->|

But a tube with metal near whole length can break down in stages:

	[--------------------------------------]
      __[.....                                 ]
      ^ [--------------------------------------]
      |      .
      | _____.__________________________________
                                               
      V ---->|                                
                                             

with a short arc sneaking out internally, sustained by the capacitance of
the air gap (low dielectric const, but a little higher than the rarefied
nothing inside, no?).

This arc would creep along until it met the other end, with the field 
strength essentially constant, as the resistance of the arc is exceedingly low
once struck.

	[--------------------------------------]
      __[****************                      ]
      ^ [--------------------------------------]
      V                 .
      v_________________._______________________
                                               


I'll wind a bit of wire around my flakey fluoro, that should fix it.

Does this make any sense??
-- 
Peter Swain - Softway Pty Ltd		(swine@softway.oz)
    79 Myrtle St, Chippendale, NSW, Australia
PHONE:	+61-2-698-2322		UUCP:		uunet!softway.oz!swine
FAX:	+61-2-699-9174		INTERNET:	swine@softway.oz.au