[time-nuts] Q/noise of Earth as an oscillator

bg bg at lysator.liu.se
Wed Jul 27 03:11:20 EDT 2016

"A note on gyros.  When located in a dynamic platform, like an airplane, the gyro needs to be located at the center of mass of the vehicle.  This way when the plane banks, pitches or yaws the gyro will only respond to the angles.  But if it's located anywhere else it will be in error.  This applies to models as well as to full size vehicles."
This is not true. You can - and people do - mount gyros (interial systems) anywhere in the rigid part of the body - wingtip mount might be a bad idea...
If the gyro is away from the center of rotation it will experience the same rotation and also an acceleration. The chosen gyro should be good enough at separating rotation from acceleration. This has not been a problem for a very long time - 40+ years - for typical aviation nav systems.
For specialized applications - say spinning munitions - where your performance is really limited by acceleration - you should keep your sensors at the center. 
The same could be said for accelerometers, oscillators and many other sensors that might have errors amplified by the extra acc.
--      Björn

Sent from my smartphone.-------- Original message --------From: Brooke Clarke <brooke at pacific.net> Date: 27/07/2016  01:00  (GMT+01:00) To: Discussion of precise time and frequency measurement <time-nuts at febo.com> Subject: Re: [time-nuts] Q/noise of Earth as an oscillator 
Hi Hal:

I resemble that remark.

Momentum and drift.  It's interesting that the drift rate depends on the physical volume.  See table at: 

Have Fun,

Brooke Clarke
The lesser of evils is still evil.

-------- Original Message --------
> attila at kinali.ch said:
>> I am not sure you can apply this definition of Q onto earth. Q is defined
>> for harmonic oscillators (or oscillators that can be approximated by an
>> harmonic oscillator) but the earth isn't oscillating, it's rotating. While,
>> for time keeping purposes, similar in nature, the physical description of
>> both are different.
> What do gyroscope-nuts use to describe the quality of their toys?

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