Hey Chris,
 
Thanks a million. That's a lot. My space is so limited hence the PS2 system
I've kept. Hmmm...  I'll take a look the general layout at the link you
provided.
I'll let you know if I have any further questions.
 
- KAreem 

  _____  

From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Monday, March 05, 2007 10:28 PM
To: psn-l@..............
Subject: Re: Getting started...


In a message dated 2007/03/05, system98765@............. writes:



The Dataq I have is the model DI-154RS. I bought some years ago...
Kareem



Hi Kareem,

       That will be OK. It gives 12 bit resolution for a +/-10V input.
       You need a sensor, a seismic amplifier/filter, the ADC, a suitable
power supply, a data recording and analysis program, a computer to record
and analyse the signals and a time check system. The computer may need a
modem to download programs, do time checks, send and receive sample data
etc.
       The time check system may be an on-line timing signal, radio or GPS.
This is the 'unexpected extra'. The software clocks on modern computers
cannot be relied upon to within 30 sec per day! This is hopelessly
inaccurate for seismic recording, when a P wave has a velocity of about 8
km/sec. A 30 sec time error may give over 150 miles error in the epicentre
position. You need to know the time correct to about a second.
       It is not too difficult to make a Lehman using electromagnetic
damping and piano wire, or ball on a plane, or crossed cylinder type
suspensions. This should allow you to set the period to over 20 sec fairly
easily - many of the surface waves are about this period. It is a 'good
idea' to make a really rigid cross braced T type frame to support ALL the
components INCLUDING the damper and the sensor magnets. Make the arm and
mass out of non magnetic materials and put the sense and damper magnets on
the base frame. You set up the arm, sensor and damper alignment first and
then set the cross balance and period using three levelling screws on the
frame.   
       See http://www.jclahr.com/science/psn/chapman/school/MKII/index.html
for a general layout. This seismometer was made in a machine shop. It uses a
SS ball on a carbide plane and a wire suspension. The brass mass is at the
end of the arm, then comes the quad sense magnet and the white pickup coil,
then the suspension block and then the damping plate + the quad sliding
magnet. The sense arm is about 2 ft long, the base about 2 ft 6 in and the
frame height about 1 ft 6 in. I use 3" x 1" x 1/8" thick U Channel Al, large
8" triangular x 3/16" thick bolt on Al corner plates and 1/4" SS bolts. 
       {Point and knife edge suspensions may severely limit the period and
are not likely to be satisfactory long term. Oil damping is strongly
temperature dependant and messy. Oil 'creeps' slowly over most surfaces and
then attracts dust. Systems which use separate mounting/damping/sensing
components may be much more difficult to set up and to adjust. You really
don't need these sort of problems.}
       You will also need a thermally insulating, completely draft proof
'inverted box' type cover. See http://pages.prodigy.net/fxc/seiscoverslg.jpg
It is quite large! I use 2" Celotex with the joints taped and glued with
polyurethane foam grouting, both from building supplies. You can make two
layer viewing windows out of clear mylar transparency copying film or
cellophane sheet. If you don't make a screening box, you will get a lot of
'noise' due to air turbulence moving the arm. You will probably need a small
heater, maybe 10 to 20 Watts inside the top of this housing to prevent air
convection noise in the late evening / early morning.
       It is up to you whether you buy or can make the amplifier/filter. You
can buy +/-12V stabilised power supplies fairly cheaply. If you buy Larry's
amplifiers, he will supply an inexpensive wall plug transformer to drive
them - the supply regulators are built into his boards.

       NOTE: A large seismometer setup can damage your wealth!
       Check your wallet out first? Hope that this helps!

       Chris Chapman 





Hey Chris,
 
Thanks a million. That's a lot. My space is so =
limited=20
hence the PS2 system I've kept. Hmmm...  I'll take a look the =
general=20
layout at the link you provided.
I'll let you know if I have =
any further=20
questions.
 
- KAreem 




From: psn-l-request@.................
[mailto:psn-l-request@............... On Behalf Of=20
ChrisAtUpw@.......
Sent: Monday, March 05, 2007 10:28=20
PM
To: psn-l@..............
Subject: Re: Getting=20
started...


In =
a message=20
dated 2007/03/05, system98765@............. writes:


The Dataq I have is the model DI-154RS. I bought some =
years=20
  ago...
Kareem

Hi=20
Kareem,

       That will be OK. It =
gives 12=20
bit resolution for a +/-10V =
input.
       You=20
need a sensor, a seismic amplifier/filter, the ADC, a suitable power =
supply, a=20
data recording and analysis program, a computer to record and analyse =
the=20
signals and a time check system. The computer may need a modem to =
download=20
programs, do time checks, send and receive sample data=20
etc.
       The time check system may =
be an=20
on-line timing signal, radio or GPS. This is the 'unexpected =
extra'. The=20
software clocks on modern computers cannot be relied upon to within 30 =
sec per=20
day! This is hopelessly inaccurate for seismic recording, when a P wave =
has a=20
velocity of about 8 km/sec. A 30 sec time error may give over 150 miles =
error in=20
the epicentre position. You need to know the time correct to about a=20
second.
       It is not too difficult =
to make=20
a Lehman using electromagnetic damping and piano wire, or ball on a =
plane, or=20
crossed cylinder type suspensions. This should allow you to set the =
period to=20
over 20 sec fairly easily - many of the surface waves are about this =
period. It=20
is a 'good idea' to make a really rigid cross braced T type frame to =
support ALL=20
the components INCLUDING the damper and the sensor magnets. Make the arm =
and=20
mass out of non magnetic materials and put the sense and damper magnets =
on the=20
base frame. You set up the arm, sensor and damper alignment first and =
then set=20
the cross balance and period using three levelling screws on the=20
frame.   
       See=20
http://www.jclahr.com/science/psn/chapman/school/MKII/index.html for a =
general=20
layout. This seismometer was made in a machine shop. It uses a SS ball =
on a=20
carbide plane and a wire suspension. The brass mass is at the end of the =
arm,=20
then comes the quad sense magnet and the white pickup coil, then the =
suspension=20
block and then the damping plate + the quad sliding magnet. The sense =
arm is=20
about 2 ft long, the base about 2 ft 6 in and the frame height about 1 =
ft 6 in.=20
I use 3" x 1" x 1/8" thick U Channel Al, large 8" triangular x 3/16" =
thick bolt=20
on Al corner plates and 1/4" SS bolts. =

      =20
{Point and knife edge suspensions may severely limit the period and are =
not=20
likely to be satisfactory long term. Oil damping is strongly temperature =

dependant and messy. Oil 'creeps' slowly over most surfaces and then =
attracts=20
dust. Systems which use separate mounting/damping/sensing components may =
be much=20
more difficult to set up and to adjust. You really don't need these sort =
of=20
problems.}
       You will also need a=20
thermally insulating, completely draft proof 'inverted box' type cover. =
See=20
http://pages.prodigy.net/fxc/seiscoverslg.jpg  It is quite large! I =
use 2"=20
Celotex with the joints taped and glued with polyurethane foam grouting, =
both=20
from building supplies. You can make two layer viewing windows out of =
clear=20
mylar transparency copying film or cellophane sheet. If you don't make a =

screening box, you will get a lot of 'noise' due to air turbulence =
moving the=20
arm. You will probably need a small heater, maybe 10 to 20 Watts inside =
the top=20
of this housing to prevent air convection noise in the late evening / =
early=20
morning.
       It is up to you whether =
you buy=20
or can make the amplifier/filter. You can buy +/-12V stabilised power =
supplies=20
fairly cheaply. If you buy Larry's amplifiers, he will supply an =
inexpensive=20
wall plug transformer to drive them - the supply regulators are built =
into his=20
boards.

       NOTE: A large =
seismometer=20
setup can damage your wealth!
       =
Check your=20
wallet out first? Hope that this=20
helps!

       Chris Chapman=20