[time-nuts] Slightly OT: inexpensive USB analog-digitalconverter?

[Didier Juges]

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Poul-Henning Kamp
> Sent: Friday, January 18, 2008 3:58 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Slightly OT: inexpensive USB 
> analog-digitalconverter?
> 
> 
> The measurement errors are static and can be calibrated out, 
> the major one I found is stray magnetic fields.
> 

We use those and sensitivity to stray fields is indeed the most significant
beef I have with them (low bandwidth being another, and drift being the
icing on the cake :-)

I have not looked at their complete line, and maybe I should, but those we
use have a nominal output for zero current that is not zero volts, so they
require a differentiual amplifier and an additional voltage reference which
brings its own set of problem and complexity.

However, it's easy to get 1500VAC isolation (as I am required in the
application where I use them) and DC coupling.

Bottom line, if you can live with the moderate precision they offer
off-the-shelf, they are great, but don't try to improve on it or you'll hit
all sorts of brick walls.

Didier KO4BB

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8:23 PM