Hi Folks, Thanks for the advise on vertical sensors, You all have such =
great incite and background on these subjects.  Making the best of this =
mailing list save me alot of wasted time and effort.

I am still trying to eliminate my daytime noise, or at least identify =
it.  Thanks, to those who are trying to help.  It was suggested I remove =
the magnet from the coil area to see if the noise continued, if so it =
might be electrical, like RF, communications etc. using the coil and =
cables as antenna. During a noisy hour I remove the magnet, from the =
coil.    All the noise disappeared, the helicorer was just a flat line. =
After a while, I reinstalled the magnet surrounding the coil and the =
noise reappeared.  Note: I only get these spikes between 8am and 5pm, =
the night time hours are very quiet.
Q.  Should I conclude that this means that it can not be electrical, ie, =
radio interference, but must be something creating vibrations?

Q. On a different subject.  Thanks to your input, I now have a better =
understanding of LaCoste zero length spring suspension, and how it is =
applied.
But I don't understand (what is zero length) or how to find if a spring =
is zero length.  Perhaps someone could walk me thru this using a "screen =
door spring" as an example.

Thanks, Ted
  ----- Original Message -----=20
  From: John or Jan Lahr=20
  To: psn-l@.................
  Sent: Wednesday, November 29, 2006 9:55 AM
  Subject: Re: School project


  I've posted pictures of a simple seismic system made from wood here:
  http://jclahr.com/science/psn/wooden/
  The natural period is a function of the tilt of the spring.  As it =
becomes more horizontal (by attaching the top of the spring lower on the =
mast) the period becomes longer.  However, if one tries to make the =
period too long the pendulum will become unstable and it will be hard to =
keep it from drifting to the upper or lower stop.

  At 02:10 PM 11/28/2006, you wrote:

    Hi Folks,  Some discussion on a simple vertical seismometer got me =
to thinking about a possible school project for the kids.  At one time, =
I found a simple vertical sensor on the internet, it used pvc pipe and a =
small 9"? spring.  I built it but never tested it because I had an idea =
the coil and magnet were just too undersized.  It probably works but =
would require some strong amplification, further more, I have no idea =
what the period would be.
    =20
    I wonder if one could use a "Slinky"  a toy spring used by kids? =
They are about 3" in dia. and collapsed about 5" tall.  I think I will =
get one and suspend it vertically, to check its suspended length and its =
natural resonance.  I have no idea how long the spring would expand =
under its own weight?   But let's say under 8 feet. If so, maybe it =
could be hung from the ceiling and the coil and mass would be near the =
floor?


   A sensitive seismic system must be covered to prevent air currents =
from causing vibrations much larger than those generated by earthquakes. =
 A vertical system will have to be very tall, and thus difficult to =
enclose.



    It just might be something kids would enjoy.  =20

  Yes, indeed.  This would demonstrate the concept of a seismic sensor =
but would not be very good for detecting earthquakes.


    Q. 1.  If I pull down on a spring and release it, it will move up =
and down, until it come to rest, if each cycle is 1 sec, (say a very =
long spring), is that its natural period? Yes, one full cycle is the =
natural period.
    Q. 2. If I put a mass on the end of the spring, will it move slower? =
  Yes.  If so, is that, now its period?     Maybe 2 or 3 seconds?
    Q. 3. If I could work out the construction details, what period =
should I target for a vertical sensor?  The AS-1 seismic systems have a =
natural period of 1.6 seconds.  To see surface waves the electronics =
with a period of 20 seconds, the electronics have to greatly boost the =
low frequencies.
    Q. 4. Are there any websites or information on using long vertical =
springs?

   I've posted various designs on my web site:  =
http://jclahr.com/science/psn/

  Keep us posted what you come up with!

  John










Hi Folks, Thanks for the advise on =
vertical=20
sensors, You all have such great incite and background on these =
subjects. =20
Making the best of this mailing list save me alot of wasted time and=20
effort.
 
I am still trying to eliminate my =
daytime noise, or=20
at least identify it.  Thanks, to those who are trying to =
help. =20
It was suggested I remove the magnet from the coil area to see if =
the noise=20
continued, if so it might be electrical, like RF, communications=20
etc. using the coil and cables as antenna. During a noisy hour =
I=20
remove the magnet, from the coil.    All the noise =
disappeared,=20
the helicorer was just a flat line. After a while, I reinstalled the magnet surrounding the coil and the =
noise=20
reappeared.  Note: I only get these spikes between 8am and 5pm, the =
night=20
time hours are very quiet.
Q.  Should I conclude that this =
means that it=20
can not be electrical, ie, radio interference, but must be something =
creating=20
vibrations?
 
Q. On a different subject.  Thanks =
to your=20
input, I now have a better understanding of LaCoste zero length spring=20
suspension, and how it is applied.
But I don't understand (what is zero=20
length) or how to find if a spring is zero length.  Perhaps =
someone=20
could walk me thru this using a "screen door spring" as an =
example.
 
Thanks, Ted

  
----- Original Message ----- 
  From:=20
  John or =
Jan Lahr=20
  
  
To: psn-l@.............. 
  
Sent: Wednesday, November 29, =
2006 9:55=20
  AM
  
Subject: Re: School =
project
  

I've posted pictures of a simple =
seismic=20
  system made from wood here:
http://jclahr.com/science/psn/wooden/
The =
natural=20
  period is a function of the tilt of the spring.  As it becomes =
more=20
  horizontal (by attaching the top of the spring lower on the mast) the =
period=20
  becomes longer.  However, if one tries to make the period too =
long the=20
  pendulum will become unstable and it will be hard to keep it from =
drifting to=20
  the upper or lower stop.

At 02:10 PM 11/28/2006, you =
wrote:

  
Hi =
Folks,  Some=20
    discussion on a simple vertical seismometer got me to thinking about =
a=20
    possible school project for the kids.  At one time, I found a =
simple=20
    vertical sensor on the internet, it used pvc pipe and a small 9"?=20
    spring.  I built it but never tested it because I had an idea =
the coil=20
    and magnet were just too undersized.  It probably works but =
would=20
    require some strong amplification, further more, I have no idea what =
the=20
    period would be.
 
I wonder if one =
could use=20
    a "Slinky"  a toy spring used by kids? They are about 3" in =
dia. and=20
    collapsed about 5" tall.  I think I will get one and suspend it =

    vertically, to check its suspended length and its natural =
resonance.  I=20
    have no idea how long the spring would expand under its own=20
    weight?   But let's say under 8 feet. If so, maybe it =
could be=20
    hung from the ceiling and the coil and mass would be near the=20
  floor?


 A sensitive=20
  seismic system must be covered to prevent air currents from causing =
vibrations=20
  much larger than those generated by earthquakes.  A vertical =
system will=20
  have to be very tall, and thus difficult to enclose.


  

It =
just might be=20
    something kids would enjoy.   =

Yes, indeed.  This would demonstrate the concept =
of a=20
  seismic sensor but would not be very good for detecting=20
  earthquakes.


  
Q. =
1.  If I=20
    pull down on a spring and release it, it will move up and down, =
until it=20
    come to rest, if each cycle is 1 sec, (say a very long spring), is =
that its=20
    natural period? Yes, one full =
cycle is the=20
    natural period.
Q. 2. If I put a mass on =
the end of=20
    the spring, will it move slower?   Yes.  If so, is that, now its=20
    period?     Maybe 2 or 3 seconds?
Q. 3. If I =
could=20
    work out the construction details, what period should I target for a =

    vertical sensor?  The =
AS-1 seismic=20
    systems have a natural period of 1.6 seconds.  To see surface =
waves the=20
    electronics with a period of 20 seconds, the electronics have to =
greatly=20
    boost the low frequencies.
Q. 4. Are there =
any=20
    websites or information on using long vertical=20
  springs?

 I've posted=20
  various designs on my web site:  http://jclahr.com/science/psn/

Keep us =
posted what=20
  you come up with!

John



  
   Many=20
    thanks, Ted