In a message dated 2008/07/12, paleoartifact@......... writes:

> You're right it was originally developed for a gravimeter; but recommended 
> by this Zollner for use in a seismometer.
> Haven't found this Zollner persons first name. German design of 1869. Being 
> as their is almost zero on the web, it sounds like it had "problems" of some 
> sort.  I'd think it would need a very strong boom to prevent bowing or 
> vibration; and a
> strong support frame.  

    Some of the gravimeters were made from fused silica. One problem is that 
the Zollner boom can oscillate by moving the whole boom sideways, as well as 
by rotating. I am not sure how you would set up the damping in practice. 
    The garden-gate type seismometers do have one end of the boom firmly 
located by the flexure.

The vertical single wire Wood-Andersons (horizontal sensing) of the 1920's, 
are 
> "sort-of" considered a variation.
> 
       I can't think why. W-As have an offset mass suspended by a taught 
vertical torsion wire. The torsional properties of the wire determine the 
sensitivity.

       For an itemised history see 
http://www.oge.or.at/Lecture_Seismometry.pdf

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/07/12, paleoartifact@......... writes:



You're right it was originally=20=
developed for a gravimeter; but recommended by this Zollner for use in a sei=
smometer.

Haven't found this Zollner persons first name. German design of 1869. Being=20=
as their is almost zero on the web, it sounds like it had "problems" of some=
 sort.  I'd think it would need a very strong boom to prevent bowing or=
 vibration; and a

strong support frame.  




    Some of the gravimeters were made from fused silica. One=20=
problem is that the Zollner boom can oscillate by moving the whole boom side=
ways, as well as by rotating. I am not sure how you would set up the damping=
 in practice. 

    The garden-gate type seismometers do have one end of the=20=
boom firmly located by the flexure.



The vertical single wire Wood-Andersons (horizontal sensing) of the 1920's,=20=
are 

"sort-of" considered a variati=
on.



       I can't think why. W-As have an offset=20=
mass suspended by a taught vertical torsion wire. The torsional properties o=
f the wire determine the sensitivity.



       For an itemised history see http://www.=
oge.or.at/Lecture_Seismometry.pdf



       Regards,



       Chris Chapman