On 2015-05-25 06:18, Tim wrote:
On Mon, 2015-05-25 at 03:56 -0500, g wrote:
would you presume dropping of voltage would cause a great amount of
change in a crystal's oscillation?
Seems highly tangental to the prior conversation, but possibly yes.
Essentially, it's a mechanical vibration, even at a very high rate.
If you gently pluck a guitar string while tuning it, it doesn't play the
same note as if you very harshly pluck the string. Or, to put in
another way, you pluck a string and let it ring, the note it plays goes
slightly flat before it peters out to not vibrating (the frequency
decreases).
So, I wouldn't be surprised if you kick a crystal with less voltage to
make it swing than you usually do, it mightn't do it so fast.
How far do you expect it to change, Grasshopper? Inquiring and bemused minds
want to know.
You are right in that in general changing the voltage on a crystal oscillator
will change the output frequency. Generally this is of concern to people who
build precision oscillators but not mere mortals such as computer users who are
bold enough to try to "fix" things inside their computers. We're talking single
digit parts per million frequency changes until the voltage gets low enough the
oscillator becomes unstable which may not happen before the oscillator simply stops.
The crystal oscillator frequency will change at PPM levels as voltages get
higher until one of two things happens, the crystal blank fractures or a
component in the oscillator fries.
Crystal oscillators bear no more resemblance to a guitar string than a hydra
bears to a gorilla. In one case both vibrate. In the other case both are living
creatures using DNA.
I completely fail to see why you might be concerned about the oscillator
producing a frequency of say 100.000000 MHz or 100.000100 MHz on a computer. The
oscillator will vary as much as 100 ppm with modern floor sweeping crystals from
oscillator to oscillator and over a wide temperature swing. The voltage induced
changes will be small by comparison.
{^_^} GPS Joanne
{^_^}
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