In a message dated 2006/12/10, tchannel@.............. writes:

>  I am thinking I would like to build a vertical sensor.  I have read that 
> the AS1 has a period of 1.5 seconds, but is extended electronically.
>  
> Q 1  Is there a program which does this? Maybe an article which explains it.

Hi Ted,

       In thinking that, remember that vertical seismometers are more 
difficult to build and to set up than horizontal ones. Having access to a small metal 
turning lathe and a drilling / milling machine are very helpful. Quite a lot 
of 'practical machanics' are involved and also various sources of 
constructional materials. 

       Some drawings for the AS-1 are on John Lahr's website. See 
http://jclahr.com/science/psn/as1/index.html 

       An electromagnetic damper to replace the messy oil damper is described 
at http://jclahr.com/science/psn/chapman/as1%20damping/index.html
       
       The period can be extended with the Robert' circuit or an adaption of 
it. See http://jclahr.com/science/psn/roberts/index.html 

       You can get stable periods out to about 4.5 secs with steel springs, 
but any further extension needs springs wound with / made of Ni-SpanC alloy to 
control the stiffness / temperature variations. A 'fairly happy' compromise 
might be to set up the seismometer with a steel spring for ~3 secs period and to 
then extend this to 30 secs, electronically or in software. If you do it in 
software, you really need a 16 bit ADC, since your dynamic range is reduced by 
maybe x100. Plan to cover the periods around 20 secs fairly typical of 
Rayleigh waves.

> Q 2  I have articles on the AS1 which shows its basic design. Is there an 
> article showing "how to" build your own Vertical?
> My basic questions would be over all dimensions, and locating the proper 
> spring.

       There is a drawing of a similar device built by Dewayne Hill See 
http://jclahr.com/science/psn/hill/index.html

and a prototype of a rather better construction at 
http://quake.eas.gatech.edu/Instruments/LPVERT0.htm

    It might be possible to build one like this inside a glass vessel or a 
tubular enclosure. Allan Coleman used an Al damper casing from a scrap yard. A 
serious problem with vertical sensors is that they are sensitive to air density 
changes / wind noise. These noise levels can be 100 times that of a 
horizontal seismometer.

    Also have a look at the EAS vertical and the drawings in the EAS Manual 
at http://www.eaiinfo.com/EAI2004/Index.htm This uses the ready made 60 deg 
agate bearings produced for chemical balances. However, there is no reason why 
you should not use a crossed rod Carbide suspension, or the dual foil one of the 
LPVERTO. The LP construction would enable you to add an air flotation chamber 
on the opposite side of the arm to the mass to greatly reduce atmospheric 
noise. Something like a miniature Al drinks can, drilled, emptied, rinsed out and 
then resealed?  

    Have a look at the STM-8 designed by Sean Morrissey at 
http://www.eas.slu.edu/People/STMorrissey/index.html and read his notes at 
http://psn.quake.net/info/stm-mail.zip
Keith has a working seisometer of this type with photos at 
http://www.bryantlabs.net/seismo.html  

> Q 3  On a different subject.  I am in Idaho and sure would like to find 
> someone in Idaho to share .PSN files and notes with. When I record an event I 
> would love to compare my signal with other local stations.  Please if you are 
> in the area or know of a station, near Boise, let me know.

       Look up all registered American stations? See links on the World Map 
at http://www.sydneystormcity.com/map.htm There is Don Sieber in Boise and Jan 
Marshall in Nampa, both close to you. There is also an associated contact and 
equipment list. There are also several educational groups operating across the 
USA.

       Since P waves travel at maybe 8 km  / sec you might also consider 
anyone 100 to 300 km distant?

       Can you set up a website with photos of your seismometer / 
alternatively send photos to John Lahr to display?

       Regards,

       Chris Chapman
In a me=
ssage dated 2006/12/10, tchannel@.............. writes:



 I am thinking I would like to=20=
build a vertical sensor.  I have read that the AS1 has a period of 1.5=20=
seconds, but is extended electronically.

 

Q 1  Is there a program which does this? Maybe an article which explain=
s it.




Hi Ted,



       In thinking that, remember that vertica=
l seismometers are more difficult to build and to set up than horizontal one=
s. Having access to a small metal turning lathe and a drilling / milling mac=
hine are very helpful. Quite a lot of 'practical machanics' are involved and=
 also various sources of constructional materials. 



       Some drawings for the AS-1 are on John=20=
Lahr's website. See http://jclahr.com/science/psn/as1/index.html 



       An electromagnetic damper to replace th=
e messy oil damper is described at http://jclahr.com/science/psn/chapman/as1=
%20damping/index.html

       

       The period can be extended with the Rob=
ert' circuit or an adaption of it. See http://jclahr.com/science/psn/roberts=
/index.html 



       You can get stable periods out to about=
 4.5 secs with steel springs, but any further extension needs springs wound=20=
with / made of Ni-SpanC alloy to control the stiffness / temperature variati=
ons. A 'fairly happy' compromise might be to set up the seismometer with a s=
teel spring for ~3 secs period and to then extend this to 30 secs, electroni=
cally or in software. If you do it in software, you really need a 16 bit ADC=
, since your dynamic range is reduced by maybe x100. Plan to cover the perio=
ds around 20 secs fairly typical of Rayleigh waves.



Q 2  I have articles on th=
e AS1 which shows its basic design. Is there an article showing "how to" bui=
ld your own Vertical?

My basic questions would be over all dimensions, and locating the proper spr=
ing.




       There is a drawing of a similar device=20=
built by Dewayne Hill See http://jclahr.com/science/psn/hill/index.html



and a prototype of a rather better construction at http://quake.eas.gatech.e=
du/Instruments/LPVERT0.htm



    It might be possible to build one like this inside a glas=
s vessel or a tubular enclosure. Allan Coleman used an Al damper casing from=
 a scrap yard. A serious problem with vertical sensors is that they are sens=
itive to air density changes / wind noise. These noise levels can be 100 tim=
es that of a horizontal seismometer.



    Also have a look at the EAS vertical and the drawings in=20=
the EAS Manual at http://www.eaiinfo.com/EAI2004/Index.htm This uses the rea=
dy made 60 deg agate bearings produced for chemical balances. However, there=
 is no reason why you should not use a crossed rod Carbide suspension, or th=
e dual foil one of the LPVERTO. The LP construction would enable you to add=20=
an air flotation chamber on the opposite side of the arm to the mass to grea=
tly reduce atmospheric noise. Something like a miniature Al drinks can, dril=
led, emptied, rinsed out and then resealed?  



    Have a look at the STM-8 designed by Sean Morrissey at ht=
tp://www.eas.slu.edu/People/STMorrissey/index.html and read his notes at htt=
p://psn.quake.net/info/stm-mail.zip

Keith has a working seisometer of this type with photos at http://www.bryant=
labs.net/seismo.html  



Q 3  On a different subjec=
t.  I am in Idaho and sure would like to find someone in Idaho to share=
 .PSN files and notes with. When I record an event I would love to compare m=
y signal with other local stations.  Please if you are in the area or k=
now of a station, near Boise, let me know.




       Look up all registered American station=
s? See links on the World Map at http://www.sydneystormcity.com/map.htm Ther=
e is Don Sieber in Boise and Jan Marshall in Nampa, both close to you. There=
 is also an associated contact and equipment list. There are also several ed=
ucational groups operating across the USA.



       Since P waves travel at maybe 8 km =
; / sec you might also consider anyone 100 to 300 km distant?



       Can you set up a website with photos of=
 your seismometer / alternatively send photos to John Lahr to display?



       Regards,



       Chris Chapman