[time-nuts] Portable Time Standard - Additional Clarification

Scott McGrath scmcgrath at gmail.com
Sun Jan 13 02:52:38 UTC 2019


Mechanical chonometers are still rated and the offset applied.  This was probably the earliest application of the offset with respect to the time standards of the day.  I.e. Greenwich and USNO among others.



Content by Scott
Typos by Siri

On Jan 12, 2019, at 5:15 PM, Jim Harman <j99harman at gmail.com> wrote:

I don't have modern knowledge of this, but traditionally marine
chronometers were not adjusted for precise timekeeping, but rather would be
"rated" for how much they would gain or lose per day and that correction
would be applied at the time of the astronomical observation.

Do you have an opportunity to post-process your data, i.e. record the
offset of your standard periodically so that you can interpolate the
results? That would probably make the requirements a lot less demanding.

> On Sat, Jan 12, 2019 at 4:28 PM Joe Hobart <nova at npgcable.com> wrote:
> 
> Here is more explanation:
> 
> I need a stand-alone, easily portable unit with display; the unit may be
> used
> where GPS, cell phone, or WWVB are not available.  Low power consumption is
> highly desirable.
> 
> I have seen advertisements of marine quartz chronometers listing an
> accuracy as
> good as <0.01 second/day at a constant temperature of 22 C.  Has anyone had
> experience with a marine quartz chronometers?  If so, how much did the
> accuracy
> vary with temperature?
> 
> 
> Thanks for the suggestions about pickup coils;  I had hoped a coil would
> detect
> the clock movement well enough to compare to a standard 1 PPS.  I have a
> Motorola GPS timing module and a storage oscilloscope for comparison.
> 
> Joe
> 
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-- 

--Jim Harman
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