[time-nuts] Pendulums & Atomic Clocks & Gravity
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun May 27 00:00:13 UTC 2007
Brooke Clarke wrote:
> Hi Mike:
>
> Back in the 1800s clock makers found ways to temperature compensate the
> pendulum such as putting a Mercury thermometer at the bottom, using metals with
> dissimilar expansion coefficients (Harrison used steel and bronze (no zinc
> then)) or materials with almost zero COE like Invar.
>
> The Dent clock at Greenwich in 1885 had an arenoid type compensator to remove
> barometric pressure effects, later clocks were run in vacuum.
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
>
Brooke
Invar and super Invar sound OK except that they are notoriously unstable
with the dimensions changing slowly over time even at constant temperature.
Bruce
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