PSN-L Email List Message

Subject: Re: KS36000 seismos and assumptions?
From: ChrisAtUpw@.......
Date: Sat, 28 Apr 2001 23:19:37 EDT


In a message dated 29/04/01, travis5765@........... writes:

> I can't remember who exactly said it but someone said (in this mailing list) 
> that the sensors are sealed with a gas around them to prevent noise. I am 
> assuming that if you take them apart the gas will leak out and cause noise 
> (probably the reason for the noisy channels in the first place).

       If you go the the GeoTech site http://www.geoinstr.com/ and have a 
look at their current borehole seismos, they show a stripped down photo. 
There are three gold coloured cylinders suspended in the centre section which 
are presumably the sealed units. I would expect them to have very low 
pressure gas in them. This allows cooling but inhibits convection. There will 
probably be metal glass leadthroughs somewhere for the wiring. I would 
suggest that the instruments be tested if possible and only ones with faulty 
units be stripped down. It looks as if the main case can be stripped off - 
there has to be some way to make them! The current instruments seem to have 
the electronics inside them and require 24 V DC.
       If anyone could find a manual, one of which would probably be provided 
with every instrument of this sort of cost, it would be most helpful. The 
manual of one of our 'scopes had "WHEN ALL ELSE FAILS, TRY READING THIS 
MANUAL" printed on the cover!
       Regards,

       Chris Chapman

In a message dated 29/04/01, travis5765@........... writes:


I can' t remember who exactly said it but someone said (in this mailing list)
that the sensors are sealed with a gas around them to prevent noise. I am
assuming that if you take them apart the gas will leak out and cause noise
(probably the reason for the noisy channels in the first place).


      If you g o the the GeoTech site http://www.geoinstr.com/ and have a
look at their current borehole seismos, they show a stripped down photo.
There are three gold coloured cylinders suspended in the centre section which
are presumably the sealed units. I would expect them to have very low
pressure gas in them. This allows cooling but inhibits convection. There will
probably be metal glass leadthroughs somewhere for the wiring. I would
suggest that the instruments be tested if possible and only ones with faulty
units be stripped down. It looks as if the main case can be stripped off -
there has to be some way to make them! The current instruments seem to have
the electronics inside them and require 24 V DC.
      If anyone could find a manual, one of which would probably be provided
with every instrument of this sort of cost, it would be most helpful. The
manual of one of our 'scopes had "WHEN ALL ELSE FAILS, TRY READING THIS
MANUAL" printed on the cover!
      Regards,

      Chris Chapman


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Larry Cochrane <cochrane@..............>