Hi Geoff, I get the impression you are looking for a simple answer to a
complex problem. Here is a simple answer: I use three HS10 geophones on my
system and based on word of mouth input I received from a USGS tech in 1990
he told me to start with two  500 ohm resisters in a t-pad arrangement just
to get started and work up until I got the output I desired. That said,
Chris is right-- you will need the specs from the manufacture if you want to
setup your geophones with any kind of precision . Here are two links, one to
a USGS report describing setting the damping values for the S and T
resisters in a t-pad style damping  (one resister across the coil output and
one resister in series between the coil output and one of the inputs to the
filter/amp).  Here is a link to a USGS paper and calibration results for
their sensors. http://geopubs.wr.usgs.gov/open-file/of99-434/  

Here is the link to the Stanford Geo lab calibration procedure for the L4C
geophone. http://www-ssrl.slac.stanford.edu/lcls/technotes/lcls-tn-03-6.pdf

 

I hope this helps, Regards Steve Hammond PSN San Jose, Aptos, CA. 

 

 

 

From: psnlist-request@.............. [mailto:psnlist-request@...............
On Behalf Of chrisatupw@.......
Sent: Sunday, February 05, 2012 4:42 PM
To: psnlist@..............
Subject: Re: Damping Resistor

 

Subject: Damping Resistor

Is anyone able to comment on this expression
to get a value for the damping resistor ?
.
Hi Geoff,
    Most geophones use a copper coil former, which also forms part of 
the mass. Since this is moving in the magnetic field, damping currents 
are induced in it, giving maybe 0.4 critical damping. I think that your 
formula relates to a system with no inherent damping. The manufacturers 
supply response curves for a range of damping resistors.  
    Regards,
    Chris













Hi Geoff, I get the impression you are looking for a =
simple
answer to a complex problem. Here is a simple answer: I use three HS10
geophones on my system and based on word of mouth input I received from =
a USGS
tech in 1990 he told me to start with two  500 ohm resisters in a =
t-pad
arrangement just to get started and work up until I got the output I =
desired. That
said,  Chris is right-- you will need the specs from the =
manufacture if
you want to setup your geophones with any kind of precision . Here are =
two
links, one to a USGS report describing setting the damping values for =
the S and
T resisters in a t-pad style damping  (one resister across the coil =
output
and one resister in series between the coil output and one of the inputs =
to the
filter/amp).  Here is a link to a USGS paper and calibration =
results for
their sensors. http://geopubs.wr=
..usgs.gov/open-file/of99-434/ 


Here is the link to the Stanford Geo lab calibration =
procedure
for the L4C geophone. http://www-ssrl.slac.stanford.edu/lcls/technotes/lcls-tn-03-6.pdf

 

I hope this helps, Regards Steve Hammond PSN San =
Jose,
Aptos, CA. 

 

 

 



From:=

psnlist-request@.............. [mailto:psnlist-request@............... =
On
Behalf Of chrisatupw@.......

Sent: Sunday, February 05, 2012 4:42 PM

To: psnlist@..............

Subject: Re: Damping Resistor



 



Subject: Damping Resistor

Is anyone =
able to comment on this expression
to get a =
value for the damping resistor ?
.
Hi =
Geoff,
    Most geophones use a copper =
coil former, which also forms part of 
the mass. =
Since this is moving in the magnetic field, damping currents =
are induced =
in it, giving maybe 0.4 critical damping. I think that your =
formula =
relates to a system with no inherent damping. The manufacturers =
supply =
response curves for a range of damping resistors.  =
    Regards,
    Chris