PSN-L Email List Message

Subject: Re: Newbie trying to get started
From: Mark Robinson mark.robinson@...............
Date: Sat, 21 Jun 2008 20:03:56 +1200


Steinar Midtskogen wrote:
> [ChrisAtUpw@........
> 
>>        You seem to be trying to do things the hard way!
> 
> It is also a good way to learn how things work, so I'm willing to make
> a try.
> 
>>        The SEP box is designed to plug directly into almost any old
>> PC running windows! You download the AmaSeis data logging and
>> analysis software from http:
>> //bingweb.binghamton.edu/~ajones/AmaSeis.html This gives you a WHOLE
>> SUITE of dedicated seismic programs, including both low and high
>> pass digital filters, FFT analysis and a lot more! The hard work has
>> already been done for you!
> 
> I guess, but it is the x86 Windows part which is my problem.  True, I
> can probably get a 20 year old Windows PC for free somewhere, though
> it will still add to the electricity bill (wouldn't a PC with moving
> parts, i.e. harddisk and fans, nearby the seismometer cause some
> vibrations?) and it would take up even more space in the basement
> storeroom (where I have the seismometer) which I don't really have.
> 
> My real concern is probably that I don't like to run software which
> I'm unable to modify to my needs.  No source code = no control.
> 
> Anyway, the piece of code for reading the data was trivial, just a few
> lines of C code.  And gnuplot does the plotting job for me, at least
> the plotting that can be done automatically for a web page.  All this
> was done in a few hours.
> 
> So I think the only thing I'm missing is the filter.  Does any seismic
> programs come with source code?
> 
> But I'll have a look at AmaSeis anyway, which might be useful for
> manual analysis of seismic events.  If I make my logger program store
> raw data in a way AmaSeis can read it, I don't need to run AmaSeis on
> my datalogger.  My regular PC is an AMD64 running Linux, but chances
> that AmaSeis will run on it using Wine should be good.
> 
> 
> I did make a very simple filter:
> 
>     output[i] = output[i-1] + alpha * (input[i] - output[i-1]);
> 
> and experimented with different values for alpha, but I suspect that
> this filter is too soft.

This looks like an ideal use for a slug to me.

Perhaps you could simply average every ten readings as a low pass filter.

It would also be easy to make the raw data stream available on a port to any
external application which can then do further processing. Can Amaseis swallow
such a stream ?

Nice work.
-- 
Mark
-------------
21 Jun 1990 50,000 people die as the result of an earthquake in Iran.

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