[time-nuts] Adjusting accuracy of a Casio G-Shock watch

[Don Latham]

Might want to have the watch near body temp when you adjust?
Don

----- Original Message ----- 
From: "Jim Palfreyman" <jim77742 at gmail.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Tuesday, December 14, 2010 9:16 PM
Subject: [time-nuts] Adjusting accuracy of a Casio G-Shock watch


> Fellow time-nuts.
>
> Over in another part of the internet is a group of people who love their
> Casio G-Shock watches. These digital watches have been around for decades
> and are built very well.
>
> The one I own is an "atomic" and solar model (i.e. no battery 
> replacement).
> However being in Tasmania, I cannot receive the low frequency time 
> signals.
> When I first received the watch it's accuracy was excellent. Under 10
> seconds a year. I even posted on here about it. Since then though it has
> drifted somewhat.
>
> After a ton of internet searching on how to open the case and how to 
> adjust
> these watches (this is non trivial as the models are all very different 
> and
> no instructions existed for this model - the GW-810D) I have finally 
> cracked
> it.
>
> Interestingly, the module has a pad that gives off a stepped square wave 
> at
> 32768/48 Hz. So with well calibrated equipment (which we all have of 
> course)
> it is trivial to adjust the trimmer to put the watch back to decent
> accuracy. Using the smallest adjustment of the trimmer that I could muster 
> I
> could get it down to about 0.5 in 10^6 or 1 second in around 20 days. Not 
> as
> good as when I got it - but I was probably just lucky.
>
> Over in mygshock.com they struggle with this sort of timing stuff - 
> whereas
> my big deal was opening the case!
>
> Just posting in this in case anyone here is interesting in adjusting their
> G-Shock.
>
> Jim
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