Hi Bob- Well your timing is good. =
I am getting ready to deploy 3 BH seismometers down hole and am using th=
e Mark Products L15B (4.5Hz) elements. Two deployments will be at the S=
kyWalk Bridge, AZ and 1 at the new NV State College in Henderson.
The L15B goes for ~$100/component where the better L4 (1Hz) is ~$1K/comp=
onent and is a much larger size than the geophone.
You essentially have turned my L15 geophones into a L4...T~0.2s to 1s. =
I will let you know how your filter works and THANKS......Jim
Jim O'Donnell =
Geological/Geophysical Consultant
GEOTECHNICAL APPLICATIONS
702.293.5664 geophysics@..........
702.281.9081 cell jimo17@........
-- Bobhelenmcclure@....... wrote:
I am an amateur seismographer, located in Locust Valley, NY. My statio=
n consists of home built sensors of rather short natural period. Out of =
necessity, I have developed a digital inverse filter, which allows exten=
sion of the natural period of the sensors to five or more times their na=
tural period. It took a lot of grunting and straining to perfect this fi=
lter, and I want to share it with anybody who could benefit. It ended up=
being simple to code and use. All you need to set it up is the natural =
period and damping of the sensor, and the desired filter period. It can =
be used in real time or on completed files. In case you have any need =
to enhance the performance of geophones or any other open loop sensor yo=
u operate, please refer to web page http://www.jclahr.com/science/psn=
/mcclure/filter.html This page describes the analog prototype of the f=
ilter and the pseudocode for its digital version. A mathematical analysi=
s demonstrates that the filter's frequency response is correct. This f=
ilter is implemented in my programs "WQFilter.exe" and "Heliplot.exe", w=
hich can be downloaded from http://www.jclahr.com/science/psn/mcclure/=
wdq_utilities/index.html "WQFilter.exe" is a utility program for filte=
ring WinQuake PSN Type 4 event files. "Heliplot.exe" is a program for fi=
ltering and displaying Dataq WQD format files. It would be easy for me t=
o code these applications for other file formats, including Little Endia=
n SAC binary files. Dr. Alan Jones has also incorporated this filter i=
nto "AmaSeis.exe" for filtering SAC binary format event files. However, =
the version he has coded is no longer up-to-date, and the response is no=
t quite so accurate as the latest version. All my applications are wri=
tten using Visual Basic 6.0 for Windows. Alan is currently re-coding Ama=
seis using Java, so that it can be compiled for other operating systems.=
Please note that "WQFilter.exe" also includes Butterworth filters for=
lowpass and highpass filtering. Forward, backward, and forward-backward=
filtering can be selected. If you apply both my period extending filter=
and a second order highpass backward filter to the event data, you can =
end up with a broader bandwidth file which has no phase distortion and n=
o time delay in the passband. Robert (Bob) McClure
Hi Bob- Well your timing is good.
I am getting r=
eady to deploy 3 BH seismometers down hole and am using the Mark Product=
s L15B (4.5Hz) elements. Two deployments will be at the SkyWalk Br=
idge, AZ and 1 at the new NV State College in Henderson.
The L15B goes for ~$100/component where the better L4 (1Hz) is ~$1K/c=
omponent and is a much larger size than the geophone.
You essentially=
have turned my L15 geophones into a L4...T~0.2s to 1s.
I will =
let you know how your filter works and THANKS......Jim
&nb=
sp; Jim O'Donn=
ell
=
; Geological/Geophysical Consultant
=
; GEOTECHNICA=
L APPLICATIONS
702.293.5664 geophysics@m=
ysite.com
702.281.9081 cell jimo17@........
=
-- Bobhelenmcclure@....... wrote:
I am an amateur seismographer, located in Locust Valley, NY.=
My station consists of home built sensors of rather short natural perio=
d. Out of necessity, I have developed a digital inverse filter, which al=
lows extension of the natural period of the sensors to five or more time=
s their natural period. It took a lot of grunting and straining to perfe=
ct this filter, and I want to share it with anybody who could benefit. I=
t ended up being simple to code and use. All you need to set it up is th=
e natural period and damping of the sensor, and the desired filter perio=
d. It can be used in real time or on completed files.
In case you have any need to enhance the performance of geop=
hones or any other open loop sensor you operate, please refer to web pag=
e
This page describes the analog prototype of the filter and t=
he pseudocode for its digital version. A mathematical analysis demonstra=
tes that the filter's frequency response is correct.
This filter is implemented in my programs "WQFilter.exe" and=
"Heliplot.exe", which can be downloaded from
"WQFilter.exe" is a utility program for filtering WinQuake P=
SN Type 4 event files. "Heliplot.exe" is a program for filtering and dis=
playing Dataq WQD format files. It would be easy for me to code these ap=
plications for other file formats, including Little Endian SAC binary fi=
les.
Dr. Alan Jones has also incorporated this filter into "AmaSe=
is.exe" for filtering SAC binary format event files. However, the versio=
n he has coded is no longer up-to-date, and the response is not quite so=
accurate as the latest version.
All my applications are written using Visual Basic 6.0 for W=
indows. Alan is currently re-coding Amaseis using Java, so that it can b=
e compiled for other operating systems.
Please note that "WQFilter.exe" also includes Butterworth fi=
lters for lowpass and highpass filtering. Forward, backward, and forward=
-backward filtering can be selected. If you apply both my period extendi=
ng filter and a second order highpass backward filter to the event data,=
you can end up with a broader bandwidth file which has no phase distort=
ion and no time delay in the passband.
Robert (Bob) McClure
See what's free at AOL.com.