[time-nuts] Sensing pendulum position, speed, or height

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu May 31 21:18:32 EDT 2007


Tom Van Baak wrote:
> A Measurement of the Period Stability of a Free Pendulum
> http://www.leapsecond.com/history/1996-DeMarchi-Pendulum-Stability.pdf
>
> Clever solution. His optical gap is something like 5 microns.
>
> /tvb
>
>   
An additional issue is the pointing instability of the laser used.

A position sensitive detector (lateral-effect photodiode sensor) for 
which the output is independent of the beam flux could be used however 
the noise and drift (typically <=1um/C) may be an issue.

Bruce





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