[time-nuts] EFC tracking

Didier Juges didier at cox.net
Sat Jun 26 22:06:36 UTC 2010

I can only guess at what a sound card with linearity specs approaching those of the AD kit would cost, and it's still AC coupled, and as Poul pointed out, has no long term stability spec.

To me, it sounds like a no brainer, pun intended :)

Alternately, my last HP3456A cost me about $50, and that's a 6 digit DVM with decent specs. You will need an HPIB controller though, if you do not already have one.


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-----Original Message-----
From: jimlux <jimlux at earthlink.net>
Sender: time-nuts-bounces at febo.com
Date: Sat, 26 Jun 2010 12:57:37 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] EFC tracking

Didier Juges wrote:
> Steve,
> You may want to check the "Analog Devices MiniKit for ADuC702x-series".
> http://www.google.com/search?q=Analog+Devices+MiniKit+for+ADuC702x-series
> This kit includes a 24 bit ADC and integrated ARM processor in a small PWB with all the tools and sample code to do what you want with very little code to write (you can probably use the sample code as-is).
> The kit is $30 (or $35, depending on where you look...) and you will easily spend that much building something that will not work as well using your sound card.
> Sound card ADCs are intended for audio, and I'll bet their linearity does not come close to that of the ADuC702x series, if you can even get the spec for it.

sound card ADCs, the high end 24 bit ones, are pretty darn linear, and 
have pretty good SNR as well.  120-130dB S/(N+Distortion+etc) wouldn't 
be unusual.

The surrounding circuitry is likely to be a bigger problem.  1 LSB on a 
1V p-p 24bit converter is about 60nV.

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