J=F3n
This manual explains how to set the natural frequency and also the =
dampening of a Lehman.
http://www.mutr.co.uk/images/Seismometer.pdf=20

regards
Audun
http://vindkast.no/wx_seismo

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On Behalf Of J=F3n Fr=EDmann
Sent: 16. april 2009 01:26
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=20
> measure how long it takes for the boom displacement to drop by 1/2=20
> after giving it a light touch and this would be without damping in =
place.
> Gary
>=20
>=20
>=20
>=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=20
> the change is that the top now has a hindge to make it more movable.=20
> In theory that should provide me with better frequancy. However. I=20
> continune to get the peak at 0.6Hz, even with thoise changes. The=20
> damper plate is now aluminum, not steel.
>=20
> I am not sure how well this works until I get a earthquake close to=20
> Iceland or some where in the world.
>=20
> Pictures.
>=20
> http://www.jonfr.com/myndir/v/geology/seismometer/p4150001b.jpg.html
>=20
> Regards.

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