Hoi David,

On Tue, 18 Oct 2016 05:25:35 -0500
David <davidwh...@gmail.com> wrote:

> Below 0.1 Hz it is not all that interesting; 

Depends on what you are doing ;-)

> the noise is just the
> noise of the chopper amp and flat below the chopping frequency.  I
> think Jim Williams mentioned in one of his articles that at low
> frequencies, noise and drift are effectively the same thing so

Yes, different words for the same thing.

> thermal EMF becomes a large if not the largest contributor.

Ah.. good to know. Thanks!
Any guess what the other big factors are?

> When I did it, I extended the single ended design to a fully
> differential gain of 1000 amplifier using a pair of LT1028s with a
> pair of LTC1150s for correction.  I used the noise curves to estimate
> what the integrator gain should be and after adjusting it for minimum
> noise from about 0.1 to 10 Hz, it was very close to the actual
> crossover point in the datasheet specifications.  RMS noise was
> measured by taking the standard deviation of the DC values from a
> Fluke 8505A over 10 seconds.

You wouldn't have the schematics and the measurments available somewhere?
It would be interesting to have a look at them.

BTW: Should this discussion be moved over to volt-nuts?
I kind of feel we are getting too off-topic for time-nuts.
(though my interest comes from long term time measurment)

                        Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson
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