NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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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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.
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList-@fer3.com
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