## PSN-L Email List Message

Subject: RE: Changes to my Lehman sensor
From: "Gary Lindgren" gel@.................
Date: Wed, 15 Apr 2009 16:44:15 -0700

```Jon,
Without damping give the boom a light touch, what is the natural period.
Count how many seconds it takes to make one cycle. Then count how long =
it
takes for the displacement to go from one centimeter to 1/2 centimeter. =
This
will tell you how much friction you have in your sensor.
Gary

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On
Behalf Of J=F3n Fr=EDmann
Sent: Wednesday, April 15, 2009 4:26 PM
To: psn-l@..............
Subject: RE: Changes to my Lehman sensor

Hi

There is a peak around 0.6Hz, it might be the sensor it self that peaks
like that. But it might also be natrual forces in my area that create
this peak. I am not sure yet what natrual frequancy of the sensor is.

Regards.
J=F3n Fr=EDmann.

On mi=F0, 2009-04-15 at 15:53 -0700, Gary Lindgren wrote:
> Jon,
> What is the period length of your Lehman sensor. Were you able to =
measure
> how long it takes for the boom displacement to drop by 1/2 after =
giving it
a
> light touch and this would be without damping in place.
> Gary
>=20
>=20
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>=20
> -----Original Message-----
> From: psn-l-request@.............. =
[mailto:psn-l-request@...............
On
> Behalf Of J=F3n Fr=EDmann
> Sent: Wednesday, April 15, 2009 11:20 AM
> To: psn-l@..............
> Subject: RE: Changes to my Lehman sensor
>=20
> Hi
>=20
> Here are pictures of the latest changes to my lehman sensor. One of =
the
> change is that the top now has a hindge to make it more movable. In
> theory that should provide me with better frequancy. However. I
> continune to get the peak at 0.6Hz, even with thoise changes. The =
damper
> plate is now aluminum, not steel.
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> I am not sure how well this works until I get a earthquake close to
> Iceland or some where in the world.
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> Pictures.
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> http://www.jonfr.com/myndir/v/geology/seismometer/p4150001b.jpg.html
>=20
> Regards.

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