In a message dated 24/03/2008, gel@................. writes:

Chris, 
Thank you for the  fine information. A couple questions: 
    1.  What is the period of your  Lehman.  
    2.  What D/A converter board are you  using. 



Hi Gary,
 
    You can set it up to about 30 seconds without  difficulty. This is 
largely a function of the improved suspension system.
    You need ~20 to 25 seconds for the surface waves.  The old WWSSN 
seismometers were set at 15 seconds to avoid tilt drift  problems and used flexing 
piano wire suspensions. See _http://jclahr.com/science/psn/wielandt/node10.html_ 
(http://jclahr.com/science/psn/wielandt/node10.html) 
 
    The UK SEP uses a low power 16 bit ADC in a  single channel proprietory 
system LTC1605 ? which runs with AmaSeis for use in  schools.
    It gives 1/2 bit noise at 20 SPS. Texas also make  two similar chips.
    Larry sells a good spec 16 bit board. OK with  WinQuake but check if you 
want to use it with AmaSeis? I suspect maybe  not?
    The Dataq boards are 14 bit and rather expensive in  my opinion. They 
seem to have yet to learn about signal averaging techniques for  reducing ADC 
internal noise.
    I use one of Mauro's boards which gives up to 18  bits resolution. He 
also sells 24 bit ADCs. See _http://mariottim.interfree.it/index_e.htm_ 
(http://mariottim.interfree.it/index_e.htm)  and  _http://www.sara.pg.it/sara_en.html_ 
(http://www.sara.pg.it/sara_en.html)  We  use DCF77 radio timing which covers 
Europe adequately for <$15. Similar to  your WWVB and it gives <20 milli sec 
error. But we can also use GPS timing. 
 
    Regards,
 
    Chris Chapman



   






In a message dated 24/03/2008, gel@................. writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000080 size=
=3D2>
  
Chris,
  
Thank you for t=
he=20
  fine information. A couple questions:
  

    
What is the period of your=
=20
    Lehman.=20
    
What D/A converter board a=
re you=20
    using. 

Hi Gary,
 
    You can set it up to about 30 seconds without=20
difficulty. This is largely a function of the improved suspension system.
    You need ~20 to 25 seconds for the surface wave=
s.=20
The old WWSSN seismometers were set at 15 seconds to avoid tilt drift=20
problems and used flexing piano wire suspensions. See http://jclahr.co=
m/science/psn/wielandt/node10.html
 
    The UK SEP uses a low power 16 bit ADC in=20=
a=20
single channel proprietory system LTC1605 ? which runs with AmaSeis for use=20=
in=20
schools.
    It gives 1/2 bit noise at 20 SPS. Texas also ma=
ke=20
two similar chips.
    Larry sells a good spec 16 bit board. OK with=20
WinQuake but check if you want to use it with AmaSeis? I suspect maybe=20
not?
    The Dataq boards are 14 bit and rather expensiv=
e in=20
my opinion. They seem to have yet to learn about signal averaging techniques=
 for=20
reducing ADC internal noise.
    I use one of Mauro's boards which gives up to 1=
8=20
bits resolution. He also sells 24 bit ADCs. See http://mariottim.interfre=
e.it/index_e.htm and=20
http://www.sara.pg.it/sara_en.ht=
ml We=20
use DCF77 radio timing which covers Europe adequately for <$15. Similar t=
o=20
your WWVB and it gives <20 milli sec error. But we can also use GPS timin=
g.=20

 
    Regards,
 
    Chris Chapman