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

[Bob Camp]

Hi

What is atypical about these parts is:

1) The excellent noise performance inside 10 Hz
2) The built in Nyquist filters

The first is very impressive compared to just about anything else out there.
The second is available in some, but not all similar parts.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Robert LaJeunesse
Sent: Monday, December 10, 2012 10:27 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 31bit ADC, 1000 samples per second

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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