[time-nuts] a real atomic wristwatch

Bob Camp lists at rtty.us
Wed Oct 2 18:36:40 EDT 2013


Hi

Any "real" watch or clock depends very much on things averaging out. If you look at a 5 second a year watch, it might be off by a second or two a week in some weeks….

Bob

On Oct 2, 2013, at 1:19 PM, Tim Shoppa <tshoppa at gmail.com> wrote:

> You are correct, I observe that several of my circa $100 non-WWVB quartz
> watches are good to 5 secs a year.
> 
> That 5 sec a year if I do my math right... is 1.6e-7, which is only a
> little worse than the spec of the ovened HP10811 (1e-7). Now under my
> typical use there is a 98.6 degree F oven right next to the watch most of
> the time, but I doubt that is as good as an 10811 oven :-)
> 
> That's very impressive for a mass produced miniaturized device in such an
> environment. Is there any documentation about how they achieve this? I'm
> guessing there's custom-programmed temperature compensation done at the
> factory for each unit, and maybe some aging before that, and maybe they
> even have characterized the aging well enough that it's programmed in as a
> trend as well.
> 
> Tim.
> 
> 
> On Wed, Oct 2, 2013 at 10:35 AM, Ronald Held <ronaldheld at gmail.com> wrote:
> 
>> Even if the spec is exaggerated,  What do you expect the real world
>> spec to be?  Current TC watches are hard pressed to average under
>> 5s/y.
>>       Ronald
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