PSN-L Email List Message

Subject: Noise
From: Brett Nordgren brett3nt@.............
Date: Tue, 17 Jul 2012 23:28:05 -0400


Randy,

Glad you're trying to measure noise.  The only=20
problem is that it takes two, or even better,=20
three instruments whose responses you know=20
reasonably well.  If you have them, you can make=20
some very good noise measurements.

One interesting thing we discovered was that you=20
need to have the sensitive axes of the=20
instruments aligned with each other quite=20
accurately, in our case to about 0.1=20
degree.  Otherwise the contamination of the=20
signals from ground motions at right angles will=20
affect the instruments differently and therefore looks like noise.

When you get around to doing the measurements let=20
us know.  We'll be happy to share our experiences.

We have one version of the Sleeman 3-instrument=20
noise analysis program which has been used at ASL=20
for serious measurements.  I have the MatLab=20
source and a compiled version.  In order to make=20
adaptations, I was hoping to clean up the source=20
to work with Octave as I don't have access to MatLab.

Regards,
Brett

At 11:09 AM 7/17/2012, you wrote:
>Barry,
>
>2 cents to go with yours.  Maybe we=92ll get to a cup of coffee if others=
 join.
>
>Last winter I worked through many free software=20
>programs and tips available to the PSN at no=20
>cost for calibration and testing.  Yes there are=20
>good options available.  There is much room to=20
>improve and adapt them to our specific needs and=20
>configurations but source code is available for=20
>some and for others the original programmer or=20
>designers are part of PSN.  In my opinion even=20
>as an amateur it is desirable to at least see=20
>how my station fits performance wise or to=20
>compare a change I make to my previous standard.
>
>Noise in instruments =96 I found methods to=20
>correlate instruments at the same location.  I=20
>believe they similar or same as Brett and Dave=20
>use but I have yet to try them out.
>
>Noise in location =96 John Lahr provided=20
>comparison of AS1 to NLNM along with program and=20
>code to accomplish this with any=20
>instrument.  USGS also provides PDFSA which runs=20
>on LINUX and is subject to 30 sps minimum sample=20
>rate and some file formats not easily created=20
>with current PSN software.  Both programs=20
>require instrument calibration information but=20
>in differing formats.  I suspect PDFSA could run=20
>under CygWin but have not explored or tested=20
>this.  Noise testing could be periodic and=20
>provided by one or more members or on a server=20
>without setting up all the programs individually.
>
>Accurate time =96 GPS seems to be the common=20
>standard in the US at least.  My personal=20
>opinion is that data collection methods do not=20
>maintain the GPS standard when only start time=20
>and data points are maintained.  I see=20
>collection drift caused by the operating system=20
>greatly increased by use of certain other programs on a shared computer.
>
>Data Format =96 mini-SEED format and calibration=20
>files are required for some of the programs=20
>available and this is the format available from=20
>USGS.  It is complicated and I have not found a=20
>workable direct conversion from or to PSN=20
>format. Programming a converter is beyond my=20
>expertise as is creating the calibration file format.
>
>Calibration =96 The programs from Dr Weilandt work=20
>and are fairly easy to implement in a home=20
>environment using a 2 channel AD.  I found 2=20
>ways to use them with PSN data.  One method is=20
>to simply save your PSN data as text and then=20
>edit a proper header at the beginning.  For the=20
>second method I have a conversion program from=20
>PSN to the CALEX format used by the original=20
>program.  Some way to convert the results to a=20
>SEED response file would allow use with the PDFSA noise software.
>
>My notes can be linked to=20
>here:=20
>http://mit.midco.net/rpratt/images/Calibration%20using%20free%20Programs.=
pdf=20
>
>
>An idea would be to form some loose working=20
>groups and provide ideas but I also think we=20
>should be careful not to make PSN something new=20
>people might be afraid of or feel a need to=20
>measure up.  Developing interest in seismology=20
>by students and lurkers could be our most=20
>important contribution and does not require=20
>professional grade instrument performance but=20
>yet our more skilled members should take it as=20
>far as the technology can reach.  As compared to=20
>other groups on the net we seem to have the best=20
>in respect to all members and to sharing openly=20
>our thoughts from professional to new member.
>
>Randy
>
>
>| Message 5                                                           |
>'------ ------ ------ ------ ------ ------ ------ ------ ------ ------'
>Subject: Re: diamagnetic levitation seismometer possibility
>From:    Barry Lotz 
>Date:    Mon, 16 Jul 2012 19:19:03 -0700 (PDT)
>
>---1540918134-1195055643-1342491543=3D:75038
>Content-Type: text/plain; charset=3Dus-ascii
>
>Angel & Dave
>  I agree. How do we move forward?
>My 2 cents:  I work for a structural testing and=20
>inspection lab. Our lab and inspectors comply=20
>with certain standards so that our=20
>results/inspections are credible ( eg NIST,=20
>ASTM, AWS, ICC). Maybe it would be possible to=20
>have an accepted protocol for our stations with=20
>sensor(s). I would like to comment on the items you mentioned.
>
> >"We have noisy instruments"
>    It seems possible to determine the=20
> instrument noise by maybe "nesting"? Site noise=20
> could be evaluated over "X" time during=20
> day,night or both. Could it mirror the=20
> evaluation of professional systems? It seems=20
> a  threshold could be determined for=20
> credibility station/sensor noise limits. Do we=20
> use the NLNM graph with an envelope of limits?
> >"We do not calibrate"
>    Could a accepted standardized procedure be=20
> described for horizontal and vertical sensors,=20
> that all could use? I am familiar with methods=20
> that Dave and Brett use for our FBV's.
>
> >"We do not have accurate time"
>     Would , as an example, larry's SDR program=20
> and ADC unit with GPS time be sufficient? What=20
> would be an accepted variational allowance?
> >"We do not use a standard format for data exchange"
>      Could a documented conversion program(s)=20
> be used to convert from say psn to an=20
> "standard"  format? Maybe it already exists.
> > "We do not use standard naming conventions"
>
>      Should we have a described procedure for this?
>I think Dr Weilandt has programs which could address some of the noise and
>calibration issues above. I haven't completely read it but is the NMSOP=
 what
>professionals use? Could we have something similar with more nuts and bolts
>procedures and info?
>       General agreement maybe the biggest=20
> hurdle, but I agree we should make an
>effort to have more credible stations and sensors if we desire. Maybe we=
 just
>needs some agreed upon documented standards to try to achieve.
>
>
>Regards
>Barry
>


__________________________________________________________

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.

[ Top ] [ Back ] [ Home Page ]