PSN-L Email List Message

Subject: Re: Opinion on seismometer
From: Pete Rowe ptrowe@.........
Date: Wed, 13 Jun 2007 17:04:02 -0700 (PDT)

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.

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.

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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