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

> 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.

Hi there Cap,

       I was actually looking at the KS54000 
@....................................
They give the dimensions as 98" long by 5.38" dia. I believe that this is the 
replacement for the KS36000.

> A better picture of a KS36000 is at   
> http://www.geology.smu.edu/~hayward/Txar/ks.html   

       If you go to this address and click the back button, there are photos 
of other installations.

>  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.

       There should be a circuit diagram in the Seis manual. I would expect 
the oscillator/demodulator units to be inside the main casing. A setup 
similar to that on Seans site should be OK, or even a modification of the S-G 
capacity sensor.

 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. 

       It could be gas convection after an air leak in, or electronic circuit 
noise. I would expect the units to have been evacuated using a diffusion pump 
and a cold trap and baked to ~150 C to remove all water vapour. They would 
then be filled to a fraction of a mm Hg pressure with either hydrogen or 
helium. This allows internal heat conduction, but the low pressure prevents 
convection and this is essential.

  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. 

       They could be glass seals, but it is more common to use copper pipe 
seals. The Cu pipe may be tinned with soft solder on the inside. After 
pumping, the pipe is W crimped, heated to melt the solder and cut off. With 
suitable crimp tools, clean copper pipe may be crimped and cut in the same 
operation. The outside of the cut may then be tinned with solder or coated 
with epoxy.

       I used to work with vacuum systems in a university research lab. 
       Hope that this helps.

       Regards,

       Chris Chapman
In a message dated 29/04/01, CapAAVSO@....... writes:



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.




Hi there Cap,



       I was actually looking at the KS54000 

@....................................

They give the dimensions as 98" long by 5.38" dia. I believe that this is the 

replacement for the KS36000.



A better picture of a KS36000 is at   

http://www.geology.smu.edu/~hayward/Txar/ks.html   




       If you g
o to this address and click the back button, there are photos 

of other installations.



 If Ra
ul 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.




       There sh
ould be a circuit diagram in the Seis manual. I would expect 

the oscillator/demodulator units to be inside the main casing. A setup 

similar to that on Seans site should be OK, or even a modification of the S-G 

capacity sensor.



 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. 



       It could
 be gas convection after an air leak in, or electronic circuit 

noise. I would expect the units to have been evacuated using a diffusion pump 

and a cold trap and baked to ~150 C to remove all water vapour. They would 

then be filled to a fraction of a mm Hg pressure with either hydrogen or 

helium. This allows internal heat conduction, but the low pressure prevents 

convection and this is essential.



  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. 




       They cou
ld be glass seals, but it is more common to use copper pipe 

seals. The Cu pipe may be tinned with soft solder on the inside. After 

pumping, the pipe is W crimped, heated to melt the solder and cut off. With 

suitable crimp tools, clean copper pipe may be crimped and cut in the same 

operation. The outside of the cut may then be tinned with solder or coated 

with epoxy.



       I used to work with vacuum systems in a university research lab. 

       Hope that this helps.



       Regards,



       Chris Chapman