PSN-L Email List Message
Subject: Re: Lehman sensor friction
From: Brett Nordgren brett3nt@.............
Date: Sat, 18 Apr 2009 12:22:45 -0400
One source of undamped decay that isn't much talked about is how rigid is
the support for the top wire connection. Much energy can be absorbed by
microscopic swaying of the support. Similarly, if the base is mounted on
something less rigid than bedrock, energy might be getting absorbed by the
mounting surface. Air damping is a small effect, but it could be a
factor. And, of course, there is pivot quality, which has already been
much discussed. Also, if you have a coil on the boom, it should be
open-circuited to avoid losses due to interaction with the local magnetic
Once you have minimized all those effects, you will then want to add back a
good amount of well behaved damping such as with Chris' magnetic
array. You probably don't want your Lehman to just respond to one
frequency, but would prefer it to have a range of frequencies which it will
respond to. That is what you will get when you use relatively strong
damping. Reduced sensitivity = increased band width.
At 08:26 AM 4/18/2009 -0700, you wrote:
>I am curious.
>What are typical times for Lehman half-life decay?
>What are the main causes of decay?
Public Seismic Network Mailing List (PSN-L)
[ Top ]
[ Back ]
[ Home Page ]