Re: 24 bit ADC testing

From: Bob Masta (NoSpam_at_daqarta.com)
Date: 07/19/04 

Date: Mon, 19 Jul 2004 12:31:26 GMT

On Sun, 18 Jul 2004 19:36:47 GMT, "colin"
<no.spam.for.me@ntlworld.com> wrote:

<snip>

>wich ever signal you generate you could always set the amplitude to cover
>the botom half of the range then the middle bit then the top bit, then any
>aparent change in the signal other than the offset is purly down to error in
>the ADC and any such error should show up. adding an offset shld be posible
>without introducing any error at all, infact the adc probably can do it
>

This seems like an excellent idea! The only problem would
be with ADCs that don't respond down to DC (which I think
includes sigma-delta types) or overall systems like sound cards
that always block DC at the inputs. You may not even need to
measure the DC level all that well if you are mostly looking
for small discontinuities. However, this method may not show
up small nonlinearities. Imagine a response that has a slight
curve instead of being a straight line. In any small portion of it,
it will look pretty straight to the limits you can resolve. It's
only over a long range that you notice how far you have
deviated from a straight line. To do this piecewise with a DC
bias, you would need to know the DC level to the same accuracy
you are trying to resolve. That might be harder than creating
a straight ramp in the first place!

Bob Masta
dqatechATdaqartaDOTcom
 
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