[time-nuts] Low cost synchronization

[Mike Ciholas]

On Thu, 18 Aug 2005, buehl wrote:

> The 1 Hz difference leads to the problems of 'is it +1 or -1;  

I can deal with this with a digital counter.  You will always 
know if A is ahead of B or not.

> Or at zero, there is no output to count.

Yes, this is a problem.  Perhaps it is better to make sure the 
crystals are different, like 32KHz and 38KHz.  But still, is the 
difference between them stable to 0.1ppm?  I'm skeptical 
(otherwise everyone would do it this way), but I'd be happy for 
it to be so!

> Does anyone in the group have expertise in "forced aging" of 
> crystals.  In the 'good old days' before precision trimmed 
> parts, we commonly 'aged' parts with temperature cycles and 
> voltage cycles to get past all the first year variations.  
> This gave long term stability as well as sorting out all the 
> early life failures of parts.  Would take care of the 'first 
> year drift' variable.

If it is a simple bake, that we can do.  But if it more complex 
than that, the manufacturing cost might exceed other solutions.  
I was thinking we would build the PCB (which goes through a 
reflow heat cycle), then bake the end result at 100C or something 
for an hour.  But this was just speculation on my part that it 
would help with long term aging.

I guess I would find out in a year... :-(

-- 
Mike Ciholas                            (812) 476-2721 x101
CIHOLAS Enterprises                     (812) 476-2881 fax
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