PSN-L Email List Message

Subject: Re: Opinion on seismometer
From: Larry Cochrane lcochrane@..............
Date: Wed, 13 Jun 2007 18:58:58 -0700

Hi All,

This is a reminder that you can not send attachments to the PSN-L list. If you have a 
file you would like to share with the group you will need to place it on a web/ftp 
server somewhere and send the link to the file to the list. If you do not have access 
to a web server I can place the file on my system.

If you have a PSN event file you would like to share with the group you can send them 
to event@.............. as attachments. The event file(s) will show up on this page a few minutes after my mail server 
receives the message.

Larry Cochrane
Redwood City, PSN

Pete Rowe wrote:
> Hi all
> I sent the following message with a pdf of my
> recording but it bounced back as too large for the
> group. I'm not sure how to send it any other way.
> Pete
> Here is my recording of the Guatemalan quake today. As
> Jan mentioned, my seismometer is the size of a
> shoebox, has a three second period, is critically
> damped with a resistor across the coil, has almost no
> weight on the boom, and I can see a 7.0 anywhere on
> earth. The suspension is two fine steel wires (violin
> E string) both of which are in tension. This sits on
> the dirt under my house. The noise level is higher
> than normal today due to wind in the trees. Normally,
> I have a very quiet baseline. It has been running
> almost untouched since 1988.
> regards,
> Pete Rowe
> San Jose, CA
> --- Jan Froom  wrote:
>> I can remember when Pete Rowe and I first started
>> playing around with 
>> amateur seismometers... I built a large unit with a
>> long boom with a 
>> very heavy mass. Pete built a little unit, with no
>> mass on his boom at 
>> all. I had my unit mounted on three massive concrete
>> piers... Pete set 
>> his unit on a scrap of 2X4 under his house...
>> Funny thing... we both got about the same results...
>> and Pete didn't 
>> have half the problems I had.
>> Pete finally put a small fish weight on the end of
>> his boom... I sure... 
>> simply to appease me.
>> I've also come to the conclusion that the antique
>> seismometers I've 
>> collected all have large masses and huge coils
>> simply because they had 
>> to generate enough power to drive a pen motors
>> directly, with no 
>> external amplification. With today's amplifiers and
>> technology you can 
>> do a whole lot more with a whole lot less.
>> Since the only response to my query about drum
>> recorders came from 
>> Chris... I took his advice and took an aspirin and
>> thought about my 
>> problem. I've decided to take advantage of the
>> antique nature of what I 
>> have, and capitalize on that. Part of what I've
>> tried to inspire in the 
>> kids I've worked with... is the simplicity of a
>> seismic monitoring 
>> system... the simplicity of a whole lot of "complex"
>> scientific 
>> devices... what better way then to let them see the
>> simple pieces up 
>> close... and if it looks a bit  "Rube
>> Goldbergish"... well that will be 
>> kool too.
>> Jan in Gilroy.
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