[time-nuts] uC ADC resolution (was: Poor man's oven)

Bob kb8tq kb8tq at n1k.org
Sat Jun 10 17:17:22 EDT 2017


> On Jun 10, 2017, at 5:15 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> --------
> In message <B90B65D3-5E09-4C1C-ADE1-100A0A26D418 at n1k.org>, Bob kb8tq writes:
>> If you want the controller noise to *not* be the limiting factor at an ADEV floor of 1x10^-12, 
>> that drives you to a noise floor of < 0.1 mK. You can then work through the various thermal 
>> gains to come up with a level of DAC bits that you need. You could equally as well decide
>> on a 1x10^-13 floor and / or might have a 1x10^-9 sensitivity. 

Sounds like a sound plan.


> Which gets us back to what SRS does for low noise:
> Implement the low noise stuff, the PI(D) loop, in analog, but
> tune/calibrate/adjust the analog circuitry with DAC's set (infrequently)
> by a uC.
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.

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