PSN-L Email List Message
Subject: Re: Did I get 12 second period ?
From: ChrisAtUpw@.......
Date: Mon, 25 May 2009 18:23:27 EDT
In a message dated 25/05/2009, gmvoeth@........... writes:
The floor is level, this is the same floor where I keep my geophone, with
any issues.
However, the lehman sensor appears to be this high so I can get 12 to 20
second period. I am not sure why that is.
Hi Jon,
It is the angle between the local vertical and the line joining the
centres of rotation of the top and bottom bearings which determines the
period.
_http://www.jonfr.com/myndir/v/geology/lehman/p5100003.jpg.html_
(http://www.jonfr.com/myndir/v/geology/lehman/p5100003.jpg.html) shows the
bottom bearing. You need to loosen the nuts and unscrew them so that the head of
the bolt is a few mm or more further AWAY from the bottom cross bar,
towards the mass. The tighten the nuts again. You will also have to adjust the
top suspension. Maybe adjust the top suspension so that the bolt head is
further away from the mass end?
The only problem that I am dealing with now is that once I have setup the
correct period. I sometimes find that the coil slides to the magnets and
gets stuck there. I do not know why that movment happens.
_http://www.jonfr.com/myndir/v/geology/lehman/p5100005.jpg.html_
(http://www.jonfr.com/myndir/v/geology/lehman/p5100005.jpg.html)
You have a bolt through the centre of the coil and another one suspending
it from the arm. Are these bolts, nuts, washers completely NON MAGNETIC?
eg.Brass and not nickel plated? Can you replace the metal bolt through the
coil with a nylon bolt? Maybe bolt or stick the coil to a sheet of fibreglass
/ plastic and attach this to the arm?
What metal is the plate supporting the magnet?
Regards,
Chris Chapman
In a message dated 25/05/2009, gmvoeth@........... writes:
The
floor is level, this is the same floor where I keep my geophone, with an=
y
issues.
However, the lehman sensor appears to be this high so I=
can get
12 to 20
second period. I am not sure why that is.
Hi Jon,
It is the angle between the local vertical an=
d the
line joining the centres of rotation of the top and bottom bearings which=
determines the period.
ht=
tp://www.jonfr.com/myndir/v/geology/lehman/p5100003.jpg.html show=
s
the bottom bearing. You need to loosen the nuts and unscrew them so that=
the
head of the bolt is a few mm or more further AWAY from the bottom cross ba=
r,
towards the mass. The tighten the nuts again. You will also have to=
adjust
the top suspension. Maybe adjust the top suspension so that the bolt head=
is
further away from the mass end?
The only
problem that I am dealing with now is that once I have setup the correct=
period. I sometimes find that the coil slides to the magnets and gets st=
uck
there. I do not know why that movment happens.
You have a bolt through the centre of the coi=
l and
another one suspending it from the arm. Are these bolts, nuts,
washers completely NON MAGNETIC? eg.Brass and not nickel plated? Can=
you
replace the metal bolt through the coil with a nylon bolt? Maybe bolt or=
stick
the coil to a sheet of fibreglass / plastic and attach this to the arm?
What metal is the plate supporting the
magnet?
Regards,
Chris Chapman
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