Hi Chris -

 

OOPS - I dropped part of a sentence....My fault...According to the
installation engineers at the Albuquerque Seismological Laboratory, they
have experienced  problems when the Styrofoam was in DIRECT contact with the
instrument. Under these conditions, changes in air pressure have caused
increases in ambient noise on their instruments.  I am unaware of any
problems when Styrofoam is used as a thermal shield and not in direct
contact with the instrument.    

 

Bob Hancock

 

 

 

  _____  

From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Monday, April 30, 2007 11:43
To: psn-l@..............
Subject: Re: geophone too close ?

 

In a message dated 2007/04/30, carpediem1@......... writes:




Avoid using foams or Styrofoam as they have minute air pockets in them and
as pressure changes, they will expand or contract and these changes will be
transmitted to the instrument.



Hi Bob,

       Have any problems of this sort been actually documented? We have been
using Cellotex cases for years apparently without problem. This is a sealed
cell styrofoam with two layers of glass scrim glued to the surfaces. I would
not rest my seismometer on such, but I would not expect any problems with a
Cellotex case which is supported on the floor. The total mass is low. 
       How would this be transmitted to the instrument? 

       Regards,

       Chris Chapman 
















Hi Chris =
–

 

OOPS – I dropped part of a =
sentence……….My
fault………According to the installation engineers at the
Albuquerque Seismological Laboratory, they have experienced =
 problems when
the Styrofoam was in DIRECT contact with the instrument. Under these
conditions, changes in air pressure have caused increases in ambient =
noise on their
instruments.  I am unaware of any problems when Styrofoam is used =
as a
thermal shield and not in direct contact with the instrument.  =
  

 

Bob =
Hancock

 

 

 









From:
psn-l-request@.............. [mailto:psn-l-request@............... =
On Behalf Of =
ChrisAtUpw@.......

Sent: Monday, April 30, =
2007 11:43

To: psn-l@..............

Subject: Re: geophone too =
close ?



 

In a message dated 2007/04/30, carpediem1@......... =
writes:







Avoid using foams or Styrofoam as they have minute =
air
pockets in them and

as pressure changes, they will expand or contract and these changes will =
be

transmitted to the instrument.





Hi Bob,



       Have any problems of this sort =
been
actually documented? We have been using Cellotex cases for years =
apparently
without problem. This is a sealed cell styrofoam with two layers of =
glass scrim
glued to the surfaces. I would not rest my seismometer on such, but I =
would not
expect any problems with a Cellotex case which is supported on the =
floor.
The total mass is low. 

       How would this be transmitted to =
the
instrument? 



       Regards,



       Chris Chapman =