In a message dated 4/29/01 4:25:53 AM GMT Daylight Time, ChrisAtUpw@....... 
writes:

       <<  If you go 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. >>

        Regards,
 
        Chris Chapman  >>

Hi Chris,

I believe what you see at this Geotech site is three A/D converters stacked 
in an aluminum cylinder. The physical dimensions given are 3.5 in (88.9 mm) 
diameter, 27.0 in (68.6 cm) length and weighing 6 lb. (2.73 kg). Such a small 
lightweight package could hardly contain the three seismometers. A similar 
electronics package may be inside the free KS36000 borehole seismometers. A 
better picture of a KS36000 is at   
http://www.geology.smu.edu/~hayward/Txar/ks.html   This is bigger and heavier 
and obviously is the whole unit that we are offered free for the taking. The 
outside container for this precision Geotech instrument is undoubtedly 
stainless steel so there will be no rust problem to prevent opening it and 
taking it apart. If Raul Alverez and Charles Patton go ahead with their plans 
to rescue these KS36000s I believe they will be able to remove three very 
high quality Geotech seismometers from each stainless steel cylinder. Of 
course we will have to homebrew our own electronics if none is inside the 
KS36000s. A description of the type of electronics we will need can be found 
in a description of a homemade seismometer with a capacity type sensor in the 
"Amateur scientist" section of "Scientific American Magazine" some years ago. 

We are told that they tested the KS36000s at Albuquerque and some of them are 
noisy. Other letters posted on PSN have said the seismos are sealed units 
filled with Helium which lowers the noise figure because the light Helium 
atoms create much less noise than heavier air molecules impacting on the 
capacitor plates of the sensor. Apparently the Helium has leaked out and air 
has leaked in to make them noisy. I believe I could refill the noisy sealed 
units with Helium and make them quite like they once were. At least I'd like 
to have a couple to give it a try. I can get a tank of pure Helium from my 
Welding supply dealer and I have glass blowing equipment. I would pump them 
down with a regular mechanical vacuum pump and refill them with pure Helium. 
Then I would pump the refilled Helium out and refill again with pure Helium. 
This process could be repeated several times and should end up with pure 
enough Helium inside so the unit would be as noise free as when Geotech first 
made it. 

The important thing right now is to help Raul and Charles get these KS36000s 
into a storage shed where they can take some of them apart. Once we see 
what's inside we can plan what to do next. PSN members can help by sending a 
small $$ donation to Raul and Charles. They are willing to do the work so the 
rest of us should be willing to finance the project. Even a small 
contribution will help. Our reward will be enough free precision Geotech 
seismometers for everyone 

Best regards,
Casper Hossfield
 
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