[time-nuts] DAC performance

[Richard (Rick) Karlquist]

On 7/17/2017 1:41 PM, Attila Kinali wrote:
> On Mon, 17 Jul 2017 12:07:29 -0700
> "Richard (Rick) Karlquist" <richard at karlquist.com> wrote:
> 
>> On 7/17/2017 10:54 AM, Azelio Boriani wrote:
>>> This implies that in a Rb or Cs there is not a voltage reference source?
>>>
>>
>> Yes, that's right, there is no voltage reference with a material
>> effect on stability or accuracy.
> 
> How about the temperature and C-field control? Aren't those based
> on keeping the output of a sensor stable compared to a voltage reference?
> 
> 			Attila Kinali
> 

Good oven design is typically done with thermistor/resistor bridges 
which are ratiometric and definitely don't depend on a reference.
In the 5071A, the C field is controlled with
a Zeeman splitting check, hence no reference involved.  In
older Cs standards, the C field accuracy depended on a reference
but it didn't require a very good one to get sufficient accuracy
in the C field.  In Rb standards, the C field is so crude it
is often adjusted using a pot.

Rick N6RK