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    Re: How Many Chronometers?
    From: John Huth
    Date: 2009 Sep 16, 10:11 -0400

    Quartz crystals have the great advantage that they have very little temperature dependence.   Typically, they're fabricated to have a minimum sensitivity to temperature around 25 degrees C.

    As I recall, the dependence is roughly a quadratic, and goes like the square of the difference in temperatures - departures from 25 degrees C.   The coefficient is something like 0.04 ppm/(degrees C)**2

    So, at freezing, one might expect 25 ppm shift, which is 2 seconds per day - pretty significant, if I consider that my typical systematic drift is 0.1 seconds per day at standard temp's.

    FYI - I wear my wristwatch 24/7/365 for this reason.

     


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