Hello Jim,
thank you for your answer!

Of course I understand that amateur systems do not need a 24bit A/D
converter : )

But I am wondering what is the reason why commercial seismometers have a
24bit A/D convertor.
How do you explain the need for such a hight sensitivity? (120 nano-g this
is so small!)
Don't you think that the seismic noise (assuming the eletronic noise is
reduced to minimum) is much bigger than hundrerds of nano-g ?
Do you think that commercial seismometers really use the full 24bit output
of there convertors? won't it be much enough to use 20bits (2 micro-g
resolution) ?

Francois

----- Original Message -----
From: "Jim Hannon" 
To: 
Sent: jeudi, 4. juillet 2002 18:43
Subject: Re: 24bits A/D converters & seismology


> Francios,
> Most amateur systems work quite well with much less than 24 bits. In fact
> it is very difficult to build any electronics that will have noise low
> enough to work with 24 bits of resolution. Of course if you can it is nice
> to work with as much resolution as possible. It helps with not clipping on
> very large events or missing very small ones depending on how your system
> is adjusted. You don't have to adjust the gain of the system as carefully
> with more bits as you have more room for the signal to fit within the
range
> of the A/D converter.
>
> At 05:22 PM 7/4/02 +0200, you wrote:
> >Hello dear all,
> >
> >could someone explain me why you need 24bits AD converters in seismology.
> >
> >Indeed it corresponds to 16.8millions points on a 2g scale, which thus
> >corresponds to a resolution of about 120 nano-g (10^-12g !)
> >Isn't the ambient noise much higher than this ?
> >
> >thanks in advance for "enlighting" me.
> >
> >Francois
> >
> >
>
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> Jim Hannon
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