In a message dated 28/12/2005, ian@........... writes:

Outside  I have my geophone and Lehman in an insulated waterproof enclosure 
which sits  over the concrete pad. This keeps the wind and rain out. The only 
thing I  can think of that would "damage" the geophone is that if it got really 
cold,  the spring inside the geophone would change its characteristics and 
may not  work too well.  How cold does it get?

I'm not sure that your  geophone would be anymore sensitive to the 
crashing of the waves if it  were placed outside. 


Hi Ian,
 
    If you are using one of Larry's L15B units, you  should be able to seal 
it with the "non acetic acid" type of silicone rubber  sealant OK. This should 
be good from -40 C to 70 C. The Geospace geophones seem  mostly rated from -45 
C to 100 C, but I am not sure about the plastic case  for the higher 
temperature. An alternative sealant which I use is  Blue-Tack / White-Tack from a 
stationery supplier. It is a putty like, non  hardening adhesive sold for 
attaching posters etc to walls without damaging  or staining the surface finish. It is 
not available in the USA.
 
    I agree about the environmental noise, but you  could get more wind noise 
in an outside location. This is likely in  Iceland.
 
    I use a SEQUA10 frequency extension board from 
_http://www.sara.pg.it/prod04_04_e.htm_ (http://www.sara.pg.it/prod04_04_e.htm) 
They cost E30 and extend the low frequency response of a 4.5  Hz geophone 
down to 1/10 the natural frequency, a bit like the low  frequency boost circuit 
on a HiFi amplifier. This enables you to sense both P  and S waves, at 1.0 and 
0.5 Hz, for local, regional and teleseismic events with  a 4.5 Hz geophone. It 
is a modified version of the Roberts' circuit.
 
    Regards,
 
    Chris Chapman






In a message dated 28/12/2005, ian@........... writes:
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  I have my geophone and Lehman in an insulated waterproof enclosure which s=
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  over the concrete pad. This keeps the wind and rain out. The only thi=
ng I=20
  can think of that would "damage" the geophone is that if it got really col=
d,=20
  the spring inside the geophone would change its characteristics and may no=
t=20
  work too well.  How cold does it get?

I'm not sure that your=20
  geophone would be anymore sensitive to the 
crashing of the waves if it=
=20
  were placed outside. 

Hi Ian,
 
    If you are using one of Larry's L15B units, you=
=20
should be able to seal it with the "non acetic acid" type of silicone rubber=
=20
sealant OK. This should be good from -40 C to 70 C. The Geospace geophones s=
eem=20
mostly rated from -45 C to 100 C, but I am not sure about the plastic c=
ase=20
for the higher temperature. An alternative sealant which I use is=20
Blue-Tack / White-Tack from a stationery supplier. It is a putty like, non=20
hardening adhesive sold for attaching posters etc to walls without dama=
ging=20
or staining the surface finish. It is not available in the USA.
 
    I agree about the environmental noise, but you=20
could get more wind noise in an outside location. This is likely in=20
Iceland.
 
    I use a SEQUA10 frequency extension board from=20=
http://www.sara.pg.it/prod04_=
04_e.htm
They cost E30 and extend the low frequency response of a 4.5=20
Hz geophone down to 1/10 the natural frequency, a bit like the low=
=20
frequency boost circuit on a HiFi amplifier. This enables you to sense both=20=
P=20
and S waves, at 1.0 and 0.5 Hz, for local, regional and teleseismic events w=
ith=20
a 4.5 Hz geophone. It is a modified version of the Roberts' circuit.
 
    Regards,
 
    Chris Chapman