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Re: First post: Fluorescent lighting
Tesla List wrote:
>
> >From paulmil-at-ibm-dot-netFri Oct 18 21:36:38 1996
> Date: Fri, 18 Oct 1996 02:40:19 GMT
> From: PAUL MILLOTT <paulmil-at-ibm-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: First post: Fluorescent lighting
>
<SNIP>
>
> Bert,
>
> I used a high frequency supply to light a flourescent tube and found it lit
> from one end and traveled along the tube until the whole thing was lit. Took
> about 4 seconds as I increased the power, to reach the other end. What was
> causing it to light only part of the tube and not the whole 4 feet? I never
> did find out.
>
> Paul Millott
Paul,
At low power levels, the RF energy is just enough to begin ionizing the
rarefied gas in the tube. Equilibrium is reached when the amount of RF
energy supplied is matched by the amount absorbed by the gas during
ionization. The gas releases the absorbed energy as heat and light. If
we have only a small amount of energy, only the area nearest to the
energy source will be ionized (since with single-ended operation, we
don't need to pass current through the entire length). I'm not sure why
Phil Gannt observed striations at lower power levels - some type of
standing wave phenomenon perhaps(?).
Although I've seen this effect with various gas-filled tubes, it may be
more pronounced with mercury vapor lamps as more liquid mercury may be
vaporized as the tube warms up. The local "party store" has a number of
small displays which slowly ramp power up and down on single-ended
neon-like tubes. The lit portion slowly climbs the length of the tube,
and then slowly shrinks back down - a very interesting effect that's
really fun to watch!
-- Bert --