PSN-L Email List Message

Subject: Re: Instrument quality
From: ChrisAtUpw@.......
Date: Wed, 21 Oct 2009 18:10:33 EDT


 
In a message dated 19/10/2009, rpratt@............. writes:

There are also many battles out here that  need fighting in addition to 
getting the last nanometre resolution  from a home-brew seismometer.  


Hi Randy,
 
    Thanks for the feedback and for your different  perspective.
 
    Sure, but my Email was not primarily concerned with  trying to get the 
last nanometre of sensitivity, but with whether the thing  works at all !
 
    Will the detection of only one earthquake a MONTH,  when it could and 
should be several every WEEK, either spark or  maintain any significant 
interest in any of your kids? This seems more than a  bit unlikely to me.
 
    And encouraging someone to make a considerable  effort to build 
equipment which then doesn't work will definitely kill  off ANY interest !
 
Quote: "Do your homework! A lot of folks out there have already done this,  
save yourself time, effort, and money by doing some research." 
 
    So what 'fruits' of caveman's 'research' seem  have actually made it 
through to the design?
 
    A very noisy, non linear photo detector was  chosen
    A highly temperature dependant photo emitter was  chosen The excitation 
current was neither stabilised nor temperature  compensated
    A single ended electronic construction was chosen,  which does not 
reduce any common mode effects
    A multi filament suspension was chosen
    No details of how to design the sensor to match the  frequency range of 
seismic signals seems to be given
    No details of how to design and adjust the  damper to give 0.7 critical 
damping seems to be given
 
    Getting adequate seismic detection  sensitivity is not normally a 
problem with optical, electromagnetic,  magnetic or capacitor sensors, in my 
experience. I welcome equipment and  suggestions which work. 
 
    Note that caveman had detailed drawings of a Wood  Anderson seismometer 
available to copy / inspire him. Richter used several WA  seismometers to 
develop his Earthquake Magnitude Scale in 1935, so we can assume  that they 
worked reasonably well.

For the past nine years I have been  involved with a regional science fair 
and have not seen a single seismometer  project.  

    So, having identified one of the problems,  can YOU help correct it, 
please? Is this simply because the students  download a list of project 
suggestions and seismometers are just not on it?  Provide information sources and 
design help? Maybe publicise some  seismic projects which actually DO work? 
Put them on psn? 
 
   I had one highschool teacher who let  me operate my Lehman from her 
classroom for a couple weeks each year but  now she is gone and there is zero 
interest in seismology in the area. From where  I sit there will not be any 
new seismologists to use those last bits of  resolution. 
 
    How have you been trying to get kids interested in  Seismology?

Anyone providing a spark of imagination and  an avenue of entry for 
interested young minds is making a great contribution  to seismology or more 
broadly science.  Earth science is falling out of  classroom time in favour or 
green and alternative energy.   

NOT around OUR neck of the woods!! A good  quality working Lehman was 
designed for schools and marketed from Easter 2007.  Sales since then have 
exceeded 400 systems. This is a successful project and  we expand further into 
Europe next year. See _http://www.bgs.ac.uk/schoolseismology/_ 
(http://www.bgs.ac.uk/schoolseismology/)   and  click on 'Seismometers'. 
    Remember that we have just 1/5 the population of  the USA.
    I would be quite happy to pass on some details of  the design. There is 
a handbook on the website. There is considerable enthusiasm  amongst our 
pupils for 'Real Science with Real Seismic Signals'. It is 'their'  
seismometer and small interested groups run it, analyse the quakes with help  from 
AmaSeis, plot them on a world map and keep records. They also get  considerable 
credit for having done a practical scientific project when  they apply for 
a place at University. 

What will give a student more pride and  motivation, connecting a 
professional device with no understanding of  it or constructing a caveman device and 
recording a distant quake?   We are up against Facebook and IPhones for 
kids time and energy.
Randy


    What professional devices are you considering? 
    Are you suggesting that it is not possible to  make a good quality DIY 
seismometer? 
    Where is the evidence that the caveman  device can give an even 
marginally adequate performance?
    One quake a month (maybe) will not provide much  competition for 
Facebook or an IPhone, but it might generate a  few Twitters. 
 
    A few years back, I helped one of your students  with his seismic 
project - very long range help! We discussed the design  requirements, principles 
and details. He had a friend helping with some  machining, but made the 
design choices himself. He produced a good working  seismometer and a full 
written account, complete with recordings of quakes  and comparison records from 
a local broad band seismometer. They were almost  identical. He entered 
this in a Science Fair and won a First Prize. 
    You need many more like him.
 
    What you do seem to be lacking in the USA is an  inexpensive school 
seismometer responding flat with velocity from about 5 Hz to  20 seconds. The 
response must be independant of temperature. It must be easy to  set up and 
operate. Iris seem to be insisting on a vertical sensor. It  would be 
preferable if it was compensated for variations in air pressure, since  these are 
the predominant source of sensor noise.
    What do you suggest? 
    
    Regards,
 
    Chris Chapman





In a message dated 19/10/2009, rpratt@............. writes:
There are also many battles out he= re that=20 need fighting in addition to getting the last nanometre resolu= tion=20 from a home-brew seismometer.  
Hi Randy,
 
    Thanks for the feedback and for your differen= t=20 perspective.
 
    Sure, but my Email was not primarily concerne= d with=20 trying to get the last nanometre of sensitivity, but with whether the thin= g=20 works at all !
 
    Will the detection of only one earthquake a= MONTH,=20 when it could and should be several every WEEK, either spark or= =20 maintain any significant interest in any of your kids? This seems more tha= n a=20 bit unlikely to me.
 
    And encouraging someone to make a considerabl= e=20 effort to build equipment which then doesn't work will definitely kill=20 off ANY interest !
 
Quote: "Do your homework! A lot of folks out there have already done= this,=20 save yourself time, effort, and money by doing some research."
 
    So what 'fruits' of caveman's 'research'= seem=20 have actually made it through to the design?
 
    A very noisy, non linear photo detector was= =20 chosen
    A highly temperature dependant photo emitter= was=20 chosen The excitation current was neither stabilised nor temperature=20 compensated
    A single ended electronic construction was ch= osen,=20 which does not reduce any common mode effects
    A multi filament suspension was chosen
    No details of how to design the sensor to mat= ch the=20 frequency range of seismic signals seems to be given
    No details of how to design and adjust= the=20 damper to give 0.7 critical damping seems to be given
 
    Getting adequate seismic detection=20 sensitivity is not normally a problem with optical, electromagne= tic,=20 magnetic or capacitor sensors, in my experience. I welcome equipment and= =20 suggestions which work.
 
    Note that caveman had detailed drawings of a= Wood=20 Anderson seismometer available to copy / inspire him. Richter used several= WA=20 seismometers to develop his Earthquake Magnitude Scale in 1935, so we can= assume=20 that they worked reasonably well.
For the past nine years I have= been=20 involved with a regional science fair and have not seen a single seismom= eter=20 project.  
    So, having identified one of the problems,=20 can YOU help correct it, please? Is this simply because the stud= ents=20 download a list of project suggestions and seismometers are just not= on it?=20 Provide information sources and design help? Maybe publicise som= e=20 seismic projects which actually DO work? Put them on psn?
 
   I had one highschool tea= cher who let=20 me operate my Lehman from her classroom for a couple weeks each year = but=20 now she is gone and there is zero interest in seismology in the area. From= where=20 I sit there will not be any new seismologists to use those last bits of=20 resolution. 
 
    How have you been trying to get kids interest= ed in=20 Seismology?
Anyone providing a spark of ima= gination and=20 an avenue of entry for interested young minds is making a great contribu= tion=20 to seismology or more broadly science.  Earth science is falling ou= t of=20 classroom time in favour or green and alternative energy. =20
    NOT around OUR neck of the woods!! A goo= d=20 quality working Lehman was designed for schools and marketed from Easter= 2007.=20 Sales since then have exceeded 400 systems. This is a successful project= and=20 we expand further into Europe next year. See http://www.bgs.ac.uk/schoo= lseismology/  and=20 click on 'Seismometers'.
    Remember that we have just 1/5 the population= of=20 the USA.
    I would be quite happy to pass on some detail= s of=20 the design. There is a handbook on the website. There is considerable enth= usiasm=20 amongst our pupils for 'Real Science with Real Seismic Signals'. It is 'th= eir'=20 seismometer and small interested groups run it, analyse the quakes with he= lp=20 from AmaSeis, plot them on a world map and keep records. They also ge= t=20 considerable credit for having done a practical scientific project wh= en=20 they apply for a place at University. 
What will give a student more= pride and=20 motivation, connecting a professional device with no understanding= of=20 it or constructing a caveman device and recording a distant quake?&= nbsp;=20 We are up against Facebook and IPhones for kids time and energy.<= /DIV>
Randy
    What professional devices are you considering= ?=20
    Are you suggesting that it is not possib= le to=20 make a good quality DIY seismometer?
    Where is the evidence that the cave= man=20 device can give an even marginally adequate performance?
    One quake a month (maybe) will not provide mu= ch=20 competition for Facebook or an IPhone, but it might generate a= =20 few Twitters. 
 
    A few years back, I helped one of your studen= ts=20 with his seismic project - very long range help! We discussed the design= =20 requirements, principles and details. He had a friend helping with some=20 machining, but made the design choices himself. He produced a good wo= rking=20 seismometer and a full written account, complete with recordings of= quakes=20 and comparison records from a local broad band seismometer. They were almo= st=20 identical. He entered this in a Science Fair and won a First Prize.=
    You need many more like him.
 
    What you do seem to be lacking in the USA is= an=20 inexpensive school seismometer responding flat with velocity from about 5= Hz to=20 20 seconds. The response must be independant of temperature. It must be ea= sy to=20 set up and operate. Iris seem to be insisting on a vertical sensor.= It=20 would be preferable if it was compensated for variations in air pressure,= since=20 these are the predominant source of sensor noise.
    What do you suggest? 
    
    Regards,
 
    Chris Chapman

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