[time-nuts] Most accurate small crystal

[Bob Camp]

Hi

There are whole series of papers on each of the effects you are asking about. They all have first, second, third .... order impacts. You could also add things like drive level, electric field, and (obviously) load onto your list. There are also papers on the cross correlation between issues. Things like load, drive, and temperature are indeed inter-related. 

The gotcha is that the crystal they studied  probably isn't the crystal you have. Simply put, a 2" diameter blank in a 3" glass holder is going to have different "major" issues than a 2x3mm ceramic package strip crystal.The only way to actually know the impact on the crystal you have is to measure it.  Even crystals from the same batch will have different specific issues. 

If you are looking at a bare crystal, the issues will be very different than if you are trying to model a modern OCXO. 

Best starting place - buy the CD's of the back issues of the Frequency Control Symposium. Each issue has a couple dozen papers looking at the kinds of issues you are interested in. The symposium has been running for a lot of years, there are lots of papers to dig into. 

Bob


On May 28, 2010, at 10:05 AM, Steve Rooke wrote:

> Hi Bob,
> 
> On 28 May 2010 04:32, Bob Camp <lists at rtty.us> wrote:
> 
>> There are a raft of papers on each of the sub portions of the fitting
>> process. Aging, retrace, temperature, and acceleration all have their own
>> issues and fit approaches.
>> 
>> The whole "how (and why that way) do they test a chronometer?" is something
>> there's a lot of papers on as well. Some of them date back into the 1600's.
>> 
>> Where do you want to start?
> 
> I'll probably start in the middle and figure out if I'm in the right
> place before I move from there. What I'm looking for are any docs on
> the various ways that xtal oscillators are affected, IE. drift over
> short time, long time, temp, pressure, humidity, gravitational effects
> of the Moon and the Earth, that sort of thing, things that have been
> studied and can be modelled for a xtal. I'm interested in what has
> been done by others to try and correct as much as possible, IE. ocxo
> et al, and to predict changes in an undisciplined xtal. When I look at
> the efc of my gpsdo I can see the effects of drift and temp changes
> and I'd like to look at the predictability of that. I'm excluding
> other forms of noise and xtal flips from this as they are outside any
> form of predictable control.
> 
> Thanks,
> Steve
> -- 
> Steve Rooke - ZL3TUV & G8KVD
> A man with one clock knows what time it is;
> A man with two clocks is never quite sure.
> 
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