PSN-L Email List Message
Subject: Re: Channel, 1,2 and 3?
From: Brett Nordgren Brett3mr@.............
Date: Sun, 23 Mar 2008 13:16:07 -0400
You may find that you do agree with John. I think the key word here was
'physical', i.e. a pendulum which has a rotational moment of inertia which
is significantly larger than ML^2 (L being the distance from the pivot to
the center of mass). If the difference is considerable you do, indeed,
sacrifice sensitivity to linear motion (vs a 'simple' pendulum) to obtain
the long period, as you described.
At 12:20 PM 3/23/2008 -0400, you wrote:
>In a message dated 23/03/2008, johnjan@........ writes:
>My understanding of a long period physical pendulum is that sensitivity to
>ground motion is sacrificed in order to obtain the long period.
> That is NOT my understanding in general.
> But you are using a nearly balanced pendulum, with a high moment of
> inertia but a small C of G to suspension distance, correct? This type
> have a long period but a LOUSY sensitivity to linear ground motion. They
> are however, sensitive to ground rotation.
> Longer period pendulums like the Lehman and the Romberg are very
> sensitive to linear ground motion and make good seismometers.
> Chris Chapman
My e-mail address above should be working, but if not
you can always use my mail form at: http://bnordgren.org/contactB.html
using your Web browser.
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