[time-nuts] oscillators

Bob Camp lists at rtty.us
Thu Aug 30 17:13:09 EDT 2012


Hi

It turns out that the fundamental is "not quite" 1/3 of the third overtone. You can impact the degree of offset by changing the contour of the blank. The temperature coefficient is also different on the fundamental. The net result is that you can get a pretty good thermometer reading by mixing one with the other divided by 3.

Bob

On Aug 30, 2012, at 4:37 PM, Azelio Boriani <azelio.boriani at screen.it> wrote:

> Interesting this third overtone/fundamental*3 idea but what makes the third
> overtone not equal to the fundamental*3? Is the crystal operated in series
> or parallel resonance?
> 
> On Thu, Aug 30, 2012 at 10:30 PM, Magnus Danielson <
> magnus at rubidium.dyndns.org> wrote:
> 
>> On 08/30/2012 06:33 PM, Bob Camp wrote:
>> 
>>> Hi
>>> 
>>> The fundamental / third approach is one of several possible ways to go.
>>> You
>>> can also run an SC on the B and C modes to get thermometer data. Early
>>> implementations used a pair of independent blanks, one cut to be a good
>>> thermometer. Some have even gone as far as to mount a thermistor on the
>>> crystal.
>>> 
>>> No matter what you do, it adds cost.
>>> 
>> 
>> The reason for doing it is to lower powerconsumption in critical
>> applications.
>> 
>> Cheers,
>> Magnus
>> 
>> 
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