Is it not the case that most commercial seismometers these days are
wideband instruments?  If so, they may need 24 bits to handle the
much larger dynamic range of these instruments.  Its possible that
20 bits might be enough, but vendors may have decided to go for the
extra 4 bits rather than restrict the range.  Considering the price
of a commercial instrument, the extra 4 bits probably does not add
to the cost of construction sufficiently to warrant changing the
price.  Its also possible that 24 bits (3 bytes) is preferred,
because it slightly simplifies the data processing software.
Comments?

Ron

----- Original Message -----
From: Francois 
Date: Thursday, July 4, 2002 12:04 pm
Subject: Re: 24bits A/D converters & seismology

> 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) ?

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