Hi,

I have a Mark Products L10B geophone.  It has a metal case and is fairly 
well sealed.  The lowest temperatures we normal get here is -10 C and 
inside the enclosure it will be slightly warmer.  Right now it's a balmy 
-0.1 C

The SEQUA10 looks interesting, though there isn't much detail on the 
webside.  Does it work by just boosting the lower frequencies?  If so, I 
can adjust my programmable filter to do the same thing, never thought 
about that...  Presumably this lowers the overall sensitivity of the 
device(?).  Would you move the upper frequency down too or keep it just 
above its natural frequency - 4.5 Hz?

Thanks

Ian

ChrisAtUpw@....... wrote:

> 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
> 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




  
  


Hi,



I have a Mark Products L10B geophone.  It has a metal case and is
fairly well sealed.  The lowest temperatures we normal get here is -10
C and inside the enclosure it will be slightly warmer.  Right now it's
a balmy -0.1 C



The SEQUA10 looks interesting, though there isn't much detail on the
webside.  Does it work by just boosting the lower frequencies?  If so,
I can adjust my programmable filter to do the same thing, never thought
about that...  Presumably this lowers the overall sensitivity of the
device(?).  Would you move the upper frequency down too or keep it just
above its natural frequency - 4.5 Hz?



Thanks



Ian



ChrisAtUpw@....... wrote:


  
  
  
  

  
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
  
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