Thanks for the ideas and interesting links.
         The Ashcroft XLDP looks interesting Len,  so before investing in
any kit, I will set up a float-pulley-weight system driving a 10 turn pot
etc. to try and record the max/min levels in the well.
          Len mentioned building a Wood-Anderson torsion seismograph,
inspired by the C.L.Strong book. If there is any interest I will scan the
other articles relating to seismology. I imagine the book is long out of
print, home made "X-ray machines" and "atom smashers" are probably not
encouraged these days.
Regards,
Andy

On 8 November 2010 01:33, Brett Nordgren  wrote:

> Geoff,
>
> Using a fluid as a mass is very much along the lines of what Dave Nelson
> was working on for his miniature horizontal.  It doesn't work so well for
> vertical designs, since for those you need to support the liquid column with
> something which doesn't change even slightly with temperature or outside
> pressure.  So far he hadn't found anything that works well for that.
>
> This has two helicorder traces and a picture, but Dave says that the N/S
> channel has a problem that he's going to be looking into.
> http://bnordgren.org/seismo/gif_images2.htm
>
> To see what's inside and see an analysis of its frequency response:
> http://bnordgren.org/seismo/FMES2.zip
>
> Dave's electronics extends the flat portion of its velocity response down
> to somewhat lower frequencies so that it sees teleseisms better.
> It is quite sensitive.
>
> Regards,
> Brett
>
> See:
>
>
> At 04:59 PM 11/7/2010, you wrote:
>
>> Possibly float a magnet on the surface
>> held in place by whatever and then
>> have a coil on the wall of the well ?
>>
>> or, vice versa.
>>
>> getting the stuff into place is a big wonder.
>>
>> I often thought a big water tower might make a good
>> vertical sensor if you hydraulically amplify
>> the pressure changes related to ground motion.
>> The water is a fluid and non-compressible
>> with lots of mass and momentum, every tiny undulation should
>> cause considerable pressure change.
>>
>> Sort of like a little pressure on the break pedal causes
>> big pressure in the hydraulic cylinders.
>>
>> When I look at the water tower at Falcon Field
>> at Mesa AZ, I often think of it as a potential seismometer.
>>
>> But such a thing must be dedicated only to sensing.
>>
>> Maybe a denser fluid like mercury ?
>>
>> A barometer like device that reacts to motion
>> instead of air pressure.
>>
>> geoff
>>
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSNLIST)
>
> To leave this list email PSNLIST-REQUEST@.............. with the body of
> the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
Thanks for the ideas and interesting links. 
=A0=A0=A0=A0=A0=A0=A0=A0 Th=
e Ashcroft XLDP looks interesting Len,=A0 so before investing in any kit, I=
 will set up a float-pulley-weight system driving a 10 turn pot etc. to try=
 and record the max/min levels in the well.

=A0=A0=A0=A0=A0=A0=A0=A0=A0 Len mentioned building a Wood-Anderson torsion =
seismograph, inspired by the C.L.Strong book. If there is any interest I wi=
ll scan the other articles relating to seismology. I imagine the book is lo=
ng out of print, home made "X-ray machines" and "atom smashe=
rs" are probably not encouraged these days.

Regards,
Andy

On 8 November 2010 01:33=
, Brett Nordgren <brett3nt@.............> wrote:

Geoff,



Using a fluid as a mass is very much along the lines of what Dave Nelson wa=
s working on for his miniature horizontal. =A0It doesn't work so well f=
or vertical designs, since for those you need to support the liquid column =
with something which doesn't change even slightly with temperature or o=
utside pressure. =A0So far he hadn't found anything that works well for=
 that.




This has two helicorder traces and a picture, but Dave says that the N/S ch=
annel has a problem that he's going to be looking into.

h=
ttp://bnordgren.org/seismo/gif_images2.htm



To see what's inside and see an analysis of its frequency response:

http://=
bnordgren.org/seismo/FMES2.zip



Dave's electronics extends the flat portion of its velocity response do=
wn to somewhat lower frequencies so that it sees teleseisms better.

It is quite sensitive.



Regards,

Brett



See:




At 04:59 PM 11/7/2010, you wrote:


Possibly float a magnet on the surface

held in place by whatever and then

have a coil on the wall of the well ?



or, vice versa.



getting the stuff into place is a big wonder.



I often thought a big water tower might make a good

vertical sensor if you hydraulically amplify

the pressure changes related to ground motion.

The water is a fluid and non-compressible

with lots of mass and momentum, every tiny undulation should

cause considerable pressure change.



Sort of like a little pressure on the break pedal causes

big pressure in the hydraulic cylinders.



When I look at the water tower at Falcon Field

at Mesa AZ, I often think of it as a potential seismometer.



But such a thing must be dedicated only to sensing.



Maybe a denser fluid like mercury ?



A barometer like device that reacts to motion

instead of air pressure.



geoff






__________________________________________________________



Public Seismic Network Mailing List (PSNLIST)



To leave this list email PSNLIST-REQUEST@.............. with the body of the m=
essage (first line only): unsubscribe

See h=
ttp://www.seismicnet.com/maillist.html for more information.