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Flickering LCD and Florescent Light
Name: Chris
Status: Other
Grade: Other
Location: CA
Country: United States
Date: October 2007
Question:
Dear Scientist, Recently, I have come across a flickering
phenomenon between an LCD display with a Florescent light lamp. This
lamp actually utilizes 50Hz at 220V (from Europe). After
investigation, I believe it has to do with the interference between
the screen frequency and the lamp. If I were to adjust the default
value from 77.5 Hz to approximately 99 Hz, then the phenomenon will
therefore disappeared. I was wondering would you be able to provide
some information in regards to the relationship between these type
of frequencies?
Replies:
Chris,
It sounds to me like you are viewing a form of phase interference.
Whenever there are two sources, (dual helicopter rotors, speakers,
irplane engines, etc.) operating at relatively close frequencies,
you get the interference. If I were to set up two speakers, one to
play a 50 hz tone, and the other a 75 hz tone, then we could hear
'beats'. The rate of the beats is the difference between the two
tones, so in this case, 25 hz.
That flickering effect is still there, and is quite unavoidable.
while your monitor was set to 77.5 hz, events (where the lamp was
not lit between power cycles, and the screen was refreshing) matched
up about 27.5 times per second, and were noticeable with a human eye.
When you changed to 99 hz, you increased the frequency of the
flickering to almost 50 hz, and you can no longer notice them.
Ryan Belscamper
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