In a message dated 19/11/2000, DSaum@............ writes:

> Here is some noise and signal data from my first Lehman which I
> am still debugging.  It looks like the noise is peaked near 6 seconds as
> you suggest.  Does this look OK to you?

Hi there Dave,

    Just a few thoughts. What does the output fft look like if you a) 
substitute an equivalent resistor for the coil and b) then reduce the gain of 
the input amplifier to unity? The noise below 0.05 Hz looks a bit high and I 
was wondering if it was due to the low pass filter, or to ambient noise? 
Filters made using OpAmps may have a lower inherent noise.

> During the day the record shows many spikes
> similar to what happens when someone walks near the pendulum and
> deforms the slab. I get some pretty quiet data in the middle of the night
> when the Big Macs go home

    Could be magnetic or mechanical or both. Did your fft represent the 
quietest period or was it average over the day?

    Hope the comment is helpful,

    Chris
    
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