PSN-L Email List Message

Subject: Re: Lehman Construction Questions...
From: BOB BARNS roybar@........
Date: Mon, 10 Apr 2000 10:39:43 -0400

  About your questions about a Lehman:
1.  The magnet-coil properties are not related to bit resolution.  16
bit resolution is better than 12 bit because of the greater dynamic
range achieved.  See Sean-Thomas discussion of the last few days about
dynamic range.
2.  The output of the coil is directly proportional to the strength of
the magnet and the number of turns of the coil if the geometry is the
same.  Since gain in the amplifier is cheap, getting enough signal from
the coil is rather easy if the geometry of the coil is appropriate for
the magnet.  10,000 turns (pretty easy if #40 or finer wire is used)
should be enough with a reasonable horse-shoe magnet.
3.  There is no reason to balance the boom-the balance does not affect
the period.  The length of the period depends only on the geometry of
the boom and its pivot points.
Call the point of emergence of the suspension wire from the top support
A and the pivot point at the end of the boom (the end opposite from the
magnet or coil) B.  The boom should be reasonably horizontal-say within
+/- 10 deg. The period is determined by the angle between the vertical
and the line between A and B.  If the line A-B is vertical, the period
is infinite, that is, there is no stable position for the boom.  The
period will be long (say 24 sec.) if the line A-B is slightly (say 0.25
deg.) inclined toward the far end of the boom.
  Since you are 'in central New York state', I am reasonably close-in
Berkeley Heights, NJ, which is about 25 miles due west of Manhattan. 
You are welcome to come see my Lehman.
  If the above is not clear, I would be happy to discuss this on the
'phone  908-464-6785 any time.
Bob Barns

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Larry Cochrane <cochrane@..............>