In a message dated 17/05/2005, shammon1@............. writes:

Hi, I  was thinking about simple ways to measure this and was able to use one
of  the unused channels on Larry's A/D board by splitting the unfiltered  data
from one of my sensors into it before it was filtered. After capturing  some
sample data,  I picked a nice large spike from one of the  datasets and was
able to see an approximate 60ms delay when comparing the  filtered and
unfiltered datasets. I'm using the Pete Rowe filter design  Amp/filter found
at http://pw2.netcom.com/~shammon1/equip.htm#Electronics  and this is
consistent with what I expected to see.
Regards, Steve  Hammond  PSN San Jose
Aptos, CA



Hi Steve,
 
    The component values on Pete Rowe's circuit  diagrams on your Website are 
unfortunately almost unreadable on my  computer.
    A three pole 10 Hz Butterworth filter should give  about 30 milli sec 
delay, peaking to about 40 milli sec at 8 Hz.
    If you have a Butterworth filter and wait for a  spike, you will probably 
be measuring the delay near the peak, rather than the  low frequency delay 
which applies to P & S waves.
    Regards,
 
    Chris Chapman






In a message dated 17/05/2005, shammon1@............. writes:
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=3D2>Hi, I=20
  was thinking about simple ways to measure this and was able to use one
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  the unused channels on Larry's A/D board by splitting the unfiltered=20
  data
from one of my sensors into it before it was filtered. After captu=
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  some
sample data,  I picked a nice large spike from one of the=20
  datasets and was
able to see an approximate 60ms delay when comparing t=
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  filtered and
unfiltered datasets. I'm using the Pete Rowe filter design=
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  Amp/filter found
at http://pw2.netcom.com/~shammon1/equip.htm#Electroni=
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  and this is
consistent with what I expected to see.
Regards, Steve=20
  Hammond  PSN San Jose
Aptos, CA


Hi Steve,
 
    The component values on Pete Rowe's circuit=20
diagrams on your Website are unfortunately almost unreadable on my=20
computer.
    A three pole 10 Hz Butterworth filter should gi=
ve=20
about 30 milli sec delay, peaking to about 40 milli sec at 8 Hz.
    If you have a Butterworth filter and wait for a=
=20
spike, you will probably be measuring the delay near the peak, rather than t=
he=20
low frequency delay which applies to P & S waves.
    Regards,
 
    Chris Chapman