At 02:55 PM 8/3/99 -0500, Sean-Thomas wrote:
2: Many have experimented with logarithmic amplifiers to expand the
dynamic range of seismic recording. The problem is how to deal with 
the negative side of the signal.

Quite a few years ago in Alaska we experimented with inverse hyperbolic
tangent amplifiers.  The function is linear through zero and then becomes
logarithmic for larger positive and negative values.  I think Analog Devices 
may have made these amplifiers.  We decided to use discrete gain 
steps instead because to the eye the signals just appeared to be
truncated.  This was in the pre-digital days of Develocorder film 
recording.

John

John C. Lahr
POB 1529
Golden, CO 80402
(303) 215-9913
http://lahr.org/john-jan

I am only one, But still I am one.
I cannot do everything, and because I cannot 
do everything, I will not refuse 
to do the something that I can do.
Edward Everette Hale

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