[time-nuts] 31bit ADC, 1000 samples per second

[Robert LaJeunesse]

31 bits is just a convenient word size that comes out of the on-chip filter, and 
does not really relate to performance. Better to look at SNR which, at worst 
case, is 120dB in high-res mode. That indicates performance just under 20 bits, 
typical for better monolithic sigma-delta converters. Nonetheless 20 bits 
indicates a matching reference would have to hold 1PPM over temperature, no 
simple task. 


Bob LaJeunesse



________________________________
From: Azelio Boriani <azelio.boriani at screen.it>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Mon, December 10, 2012 9:39:30 AM
Subject: Re: [time-nuts] 31bit ADC, 1000 samples per second

31-bit is 186dB... with what do you compare that device? What kind of
reference is needed?

On Sun, Dec 9, 2012 at 11:18 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> It's the "big brother" of the ADS127x parts that I mentioned a little
> while back. I'm sure it works quite well. The 127x's are fine parts. The
> internal filtering combined with the chopper is a very nice combination.
>
> Bob
>
> On Dec 9, 2012, at 5:13 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>
> >
> > I'm doing some work with a couple of geophones (long story...) and
> > stumbled across TI's ADS1282 geophone ADC.
> >
> > It has some pretty amazing specs for low frequencies, and having played
> > with the EVAL board for an evening here in my lab, I'm pretty impressed.
> >
> > People working with close-in phase-noise measurements may want to
> > consider this chip...
> >
> > --
> > 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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