[time-nuts] Soundcard sampling Re: Picking a good HP 10811

Lux, James P james.p.lux at jpl.nasa.gov
Wed Dec 3 01:23:08 UTC 2008



>
> Real AD cards with adequate performance are usually far more
> expensive than $300.
> In principle, one could build an ADC card with adequate
> performance using 4 AD7760 ADCs.
>
> Bruce
>
> ____

The AD7760 eval board is $150, and I think you need another board to hook it up to a computer.  However, if you have a couple kilobuck budget (i.e. you're doing this for work), then stacking up 4 of these eval boards might be a decent way to get started.

The AD7760s themselves are $36 each (Qty:1000).. The eval board is 4 layers, so that's within the realm of inexpensive prototyping, if you were to lay out a board.  Scrounging, etc., you could probably put something together for a few hundred bucks with pretty decent performance.

If it were me, though, I'd look at the high quality pro widgets already assembled, and spend my precious hours writing software to do the data reduction from the captured WAV files.

( I note that the DMTD box they have here at JPL (Greenhall, Kirk, and Tjoelker) is reported as having a noise floor Allan dev of <1E-17 at 1000s, driving the commercial synthesizer offset generator and two inputs with the same H-maser.. And it is a straight counter style measurement (123Hz))




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