In a message dated 29/12/2005, jonfr500@......... writes:

> Since I am in the learning business of how to use geophones and
> seismometers I did find an interesting article that people here might
> find useful. The article is in the link below, it is a pdf file.
> http://www.iris.edu/stations/seisWorkshop04/seisWorkshop.htm

Hi Jon,

       This is the link to the March 2004 Granlibakken Conference on very 
long period seismometers. 

       There is one link to Barzilai's extended period geophone, more full 
described on the Stanford Website at 
http://micromachine.stanford.edu/smssl/projects/Geophones/ 
       Neither the text, the circuit, nor the construction seem to have been 
updated or developed in the last four years. The digital detector circuit is 
quite noisy and the construction seems to be far from optimal. The external 
cylinder of a geophone was cut into two equal halves to insert a capacitative 
pickup. Slide 16 shows a noise level about 100x that of a Guralp CMG-40T and 
worse than a conventional geophone above about 0.2 Hz. This does NOT seem to be 
the best way to modify a geophone.

       Regards,

       Chris Chapman
In a message dated 29/12/2005, jonf=
r500@......... writes:



Since I am in the learning busi=
ness of how to use geophones and

seismometers I did find an interesting article that people here might

find useful. The article is in the link below, it is a pdf file.

http://www.iris.edu/stations/seisWorkshop04/seisWorkshop.htm



Hi Jon,



       This is the link to the March 2004 Gran=
libakken Conference on very long period seismometers. 



       There is one link to Barzilai's extende=
d period geophone, more full described on the Stanford Website at http://micro=
machine.stanford.edu/smssl/projects/Geophones/ 

       Neither the text, the circuit, nor the=20=
construction seem to have been updated or developed in the last four years.=20=
The digital detector circuit is quite noisy and the construction seems to be=
 far from optimal. The external cylinder of a geophone was cut into two equa=
l halves to insert a capacitative pickup. Slide 16 shows a noise level about=
 100x that of a Guralp CMG-40T and worse than a conventional geophone above=20=
about 0.2 Hz. This does NOT seem to be the best way to modify a geophone.


       Regards,



       Chris Chapman