Chris,

Excellent point on the whole boom moving sideways; I'd not thought of that.
Presumably thats probably the "vibratory/local source noise"
aspect of it.  Perhaps a partial limiting cure for that oscillation; might
be having a strong eddy current dampening plate boom centered
and dropping down abit underneath the boom.

Think I'll make a rough quick oscillating model; just to get a much
better impression of its aspects.  It will likely be interesting.

Take care, Meredith




On Sat, Jul 12, 2008 at 2:53 PM,  wrote:

> 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
Chris,
 
Excellent point on the whole boom moving sideways; I'd not thought of that.  Presumably thats probably the "vibratory/local source noise"
aspect of it.  Perhaps a partial limiting cure for that oscillation; might be having a strong eddy current dampening plate boom centered
and dropping down abit underneath the boom.    
 
Think I'll make a rough quick oscillating model; just to get a much better impression of its aspects.  It will likely be interesting.
 
Take care, Meredith  
 


 
On Sat, Jul 12, 2008 at 2:53 PM, <ChrisAtUpw@.......> wrote:


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