PSN-L Email List Message

Subject: Re: Instrumentation
From: George Bush ke6pxp@.......
Date: Thu, 01 Mar 2012 09:01:22 -0800


Brett, Bob, and Geoff-

At least in the Vertical direction. You have some chance of balancing 
gravity out in the horizontal directions.

George

At 11:38 AM 2/29/2012, you wrote:
>Bob & Geoff,
>
>I'd missed that part of the original question, and Bob is quite 
>right.  Gravity (an acceleration) and the ground motion you want to 
>see (which may also be viewed as acceleration) can't be separated 
>from each other.  When you manage to cancel out the first one, you 
>also end up canceling out the second.  Unfortunately, no way around it.
>
>Gravity is just a (huge) DC component of the same motion you want to measure.
>
>Brett
>
>At 01:55 PM 2/29/2012, Bob McClure wrote:
>>Hi Geoff,
>>
>>Making the mass of a seismometer neutrally buoyant will get you 
>>nowhere. The mass will not differentially move with respect to the 
>>frame when external acceleration is applied. You may be able to 
>>demonstrate a long period, but you will get no signal.
>>
>>Bob
>>
>>On Wed, Feb 29, 2012 at 1:40 PM, gmvoeth 
>><gmvoeth@.........> wrote:
>>Hello Mr. Nordgren,
>>
>>You speak in a way I might be able to understand.
>>
>>What I was wondering is that buoyancy can be implemented in ways
>>which might produce spring like results possibly one might
>>use a "weak spring (low weight/inches)" with whatever mass
>>in combination with buoyancy "like a submarine or ship" to
>>produce extended or lower frequencies using shorter lengths.
>>simply submerging the mass within a dense liquid may allow
>>this to happen.
>>
>>has such a thing ever been tried ?
>>
>>I saw this research ship which could be flooded
>>to float like a fising bobber ? it made me think
>>of other things like this one above.
>>
>>thanks for your responses.
>>
>>regards,
>>geoff
>
>
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Brett, Bob, and Geoff-

At least in the Vertical direction. You have some chance of balancing gravity out in the horizontal directions.

George

At 11:38 AM 2/29/2012, you wrote:
Bob & Geoff,

I'd missed that part of the original question, and Bob is quite right.  Gravity (an acceleration) and the ground motion you want to see (which may also be viewed as acceleration) can't be separated from each other.  When you manage to cancel out the first one, you also end up canceling out the second.  Unfortunately, no way around it.

Gravity is just a (huge) DC component of the same motion you want to measure.

Brett

At 01:55 PM 2/29/2012, Bob McClure wrote:
Hi Geoff,

Making the mass of a seismometer neutrally buoyant will get you nowhere. The mass will not differentially move with respect to the frame when external acceleration is applied. You may be able to demonstrate a long period, but you will get no signal.

Bob

On Wed, Feb 29, 2012 at 1:40 PM, gmvoeth << mailto:gmvoeth@.........>gmvoeth@.........> wrote:
Hello Mr. Nordgren,

You speak in a way I might be able to understand.

What I was wondering is that buoyancy can be implemented in ways
which might produce spring like results possibly one might
use a "weak spring (low weight/inches)" with whatever mass
in combination with buoyancy "like a submarine or ship" to
produce extended or lower frequencies using shorter lengths.
simply submerging the mass within a dense liquid may allow
this to happen.

has such a thing ever been tried ?

I saw this research ship which could be flooded
to float like a fising bobber ? it made me think
of other things like this one above.

thanks for your responses.

regards,
geoff


__________________________________________________________

Public Seismic Network Mailing List (PSNLIST)

To leave this list email PSNLIST-REQUEST@.............. with the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.

George


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