| Victor Roberts wrote:
|>> Anyone who disagrees with the above conclusion, please raise your
|>> hand... ;o)
|> OK - I'll raise my hand.
|> Instead of using your approach I just connect an optical
|> detector with sufficiently short response time to my
|> oscilloscope and point it at the CFL. If the trace is nor
|> flat then the light output is modulated.
|> for an oscilloscope trace of the light output of a CFL with
|> a small amount of modulation.
|> The zero level is a bit below the first division on the
|> screen, where the small arrow pointer is positioned. The
|> average output is about 40 mV and the peak-to-peak ripple is
|> about 7 to 8 mV.
| I see your objection and evidence, but I disagree that this modulation is
| "visible flickering".
| If the zero on your oscilloscope screen (as you say) is close to the lower
| arrow, then I count a modulation amplitude of something like 5, max 10%. If the
| zero is lower, the amplitude is less than 5%.
| Are you kidding me Vic? That's a practically flat signal.
Doesn't look flat to me. But maybe it is beyond your ability to sense
any flickering. Only you can tell us whether that is the case or not.
| Obviously there is a certain minimum modulation of the first oscillator in
| for the video to display a /visible/
flickering effect on the coupled
| oscillator, but we could then argue ad nauseam what should this minimum
| modulation be, in order for the flicker to qualify as "visible".
I hope you understand that the level of light changes that gets sensed as
flicker is different for different people.
| I mean, if the CFL displayed a 2% amplitude modulation, does the corresponding
| flicker qualify as "visible"? What about 0.00006%?
The lower the percentage, the fewer people would see it. I don't know if
the effect would be linear, or just what point is needed to eliminate all
people seeing it. And the effect within a person could vary as people
might not see different levels the same way.
| Let me then correct the conclusion, by adding the word "visible", which I did
| not include in my previous post (but had it on my web page regardless):
| "If the CFL pictured above displayed any _visible_
flicker, then the video
| should also have displayed flicker, as per the analysis above. But it does not.
| Hence this particular CFL does not display _visible_
I put more trust in the optical sensor than I do in a video camera,
especially if the camera has CCD technology and/or artifacts processing.
| In my eyes a modulation of 5-10% certainly does not qualify as "visible
| and is a huge improvement over magnetic ballast flickering on old fluoescent
| lamps where there is an actual shutoff of the light.
Although I have not used the kind of setup Vic did to measure the actual
light levels and changes, I do suspect I can sense flicker in a lot lower
level than you can. I do sense some degree of difference: some lights do
have more or less than others. I reference a neon night light I have as
a case with extreme flicker. CFLs are not as bad at that.
I am gradually using more and more CFLs and am putting them in places I do
not already have fluorescent lights, with the exception of long term task
lighting areas (work bench, kitchen, etc) which will stay with incandescent
until some better spectrums come out.
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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