## PSN-L Email List Message

Subject: Re: Vertical vs. Horz.
From: Barry Lotz barry_lotz@.............
Date: Tue, 22 Dec 2009 19:53:16 -0800 (PST)

```Chris
To extent to sensor period what about using winquake and imposing a 2 pole =
low pass filter to the signal's fft=A0 starting at the sensors rf?=20
On a different note , could there be a vertical component to the P wave due=
to the angle of wave to the earths tangent due to the depth of the hypocen=
ter ?

Regards
Barry
http://www.seismicvault.com

--- On Tue, 12/22/09, ChrisAtUpw@.......  wrote:

From: ChrisAtUpw@.......
Subject: Re: Vertical vs. Horz.
To: psn-l@..............
Date: Tuesday, December 22, 2009, 6:32 PM

=0A=0A =0A=0AIn a message dated 22/12/2009, brett3nt@............. writes:c=
lip-
=A0=0A=A0=A0=A0=A0The Roberts' period compensating amplifier circuit =0Ais =
probably the easiest technique for amateurs to use. It has constant gain fr=
om =0Athe LP filter down to ~ the resonant frequency rf=A0of the vertical s=
ensor, =0Aat say 1/2 Hz. See http://jclahr.com/science/psn/roberts/index.ht=
ml=A0 =0AIt was first used on geophones. =0A=A0=A0=A0=A0Below this to about=
rf / 10, (=3D 1/20 Hz) the gain =0Aincreases as 1 / f^2, so compensating t=
he f^2 falling output to give a flat =0Acharacteristic. So you can extend a=
2 second period vertical sensor out to about =0A20 seconds quite easily. E=
xtending the period much beyond x10 quickly runs into =0Anoise problems wit=
h a coil + magnet velocity detector.=A0You need two of =0Athese stages with=
=A0maximum gains of x10 (total x100 at 20 =0Aseconds)=A0linked by a 2 pole =
high pass filter at ~ 1/30 Hz. Lennartz use a =0Asystem like this. So do I =
and it works fine.=0A=A0=A0=A0=A0Direct digital period compensation probabl=
y works =0Abest with 24 bit ADCs. The French use it on their schools system=
.. 16 bit ADCs =0Amay only show a few counts (1/100 the rest of the signal) =
at x10 period, unless =0Athe gain is quite high and it may be partly masked=
=A0by electronic =0Anoise.=0A=A0=0A=A0=A0=A0=A0Regards,=0A=A0=0A=A0=A0=A0=

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ChrisTo extent to sensor period what abou=
t using winquake and imposing a 2 pole low pass filter to the signal's fft  starting at the se=
nsors rf? On a different note , could there be a vertical component to =
the P wave due to the angle of wave to the earths tangent due to the depth =
of the hypocenter ?RegardsBarryhttp://www.seismicvault.com=
--- On Tue, 12/22/09, ChrisAtUpw@....... <ChrisAtUpw@......
om> wrote:From: ChrisAtUpw@.....
com <ChrisAtUpw@.......>Subject: Re: Vertical vs. Horz.To: ps=
n-l@..............Date: Tuesday, December 22, 2009, 6:32 PM=0A=0A =0A=0AIn a message dated 22/12/2009, brett3nt=
@............. writes:clip- =0A  &=
nbsp; The Roberts' period compensating amplifier circuit =0Ais probabl=
y the easiest technique for amateurs to use. It has constant gain from =0At=
he LP filter down to ~ the resonant frequency rf of the vertical senso=
r, =0Aat say 1/2 Hz. See http://jclahr.com/science/psn/roberts/index.h=
tml  =0AIt was first used on geophones. =0A   =
Below this to about rf / 10, (=3D 1/20 Hz) the gain =0Aincreases as 1=
/ f^2, so compensating the f^2 falling output to give a flat =0Acharacteri=
stic. So you can extend a 2 second period vertical sensor out to about =0A2=
0 seconds quite easily. Extending the period much beyond x10 quickly runs i=
nto =0Anoise problems with a coil + magnet velocity detector. You need=
two of =0Athese stages with maximum gains of x10 (total x100 at 20 =
=0Aseconds) linked by a 2 pole high pass filter at ~ 1/30 Hz. Lennartz=
use a =0Asystem like this. So do I and it works fine.=0A &=
nbsp;  Direct digital period compensation probably works =0Abest =
with 24 bit ADCs. The French use it on their schools system. 16 bit ADCs =
=0Amay only show a few counts (1/100 the rest of the signal) at x10 period,=
unless =0Athe gain is quite high and it may be partly masked by elect=
ronic =0Anoise.=0A =0A    Re=
gards,=0A =0A    Chris Chapm=
an=0A
```