Index of Files
This is an index of the files available here for
download. Click on the filename to download it with your Web browser.
Some browsers provide more options if you right-click.
Check back often, as I intend to add new files and updates as work
progresses. (Use your browser's refresh/reload to see the latest
sts1solve.zip Updated October 5, 2004
An analysis of a fixed-end astatic leaf spring vertical seismometer,
using the STS-1 vertical as a model. Requires Excel 97 or later. With
documentation in .rtf format. May be modified to analyze similar designs.
Unzips to sts1solve.xls (642k) and sts1solve.rtf (2,878k).
sts1docs.zip Updated October 5, 2004 - 365k
The documentation only, for the the above system. Identical contents to the sts1docs.rtf file contained in sts1solve.zip, above.
Unzips to sts1docs.pdf (928k)
feedback.pdf Updated November 4, 1998
A short tutorial on feedback system analysis and design. Previously
part of loop2.pdf.
Part I of a series.
complex.pdf Updated November
23, 1998 - 15k
This is a short tutorial on complex variables, as needed for the analysis
of the STM-8 loop.
Part II of a series.
November 28, 1998 - 91k
This is an ongoing mathematical analysis of the feedback loop properties
of a force-feedback seismograph. Part III of a series.
STM-8 block diagram and definitions of the blocks. Both forward
and feedback paths analyzed and results graphed along with loop-gain and
response curves for velocity input only. Includes asymptote and corner-frequency
formulas and evaluation of how some individual components are affecting
the system. Matches S-T Morrissey's data quite well. Considerable
explanatory detail added to mathematics sections. Short section on
design approach for seismometer loops in general. Work still
in progress. Plan to take a look at how the loop deals with noise
and large signals.
driver2.pdf Updated May
20, 2000 - 46k
Suggestions for modifying the STM-8 driver circuit and P/I/D branches
in order to improve DC stability and resistance to spring creep and other
slowly-varying forces. Incorporates suggestions received from several
sources on the previously proposed design modifications. Addendum
added to address noise issues raised by S-T Morrissey.
Updated October 5, 2004 - 179k
How to measure the loop gain of a force feedback seismometer using
an oscillator and oscilloscope. This is packed with real world advice
on how to measure and interpret the system loop gain. Added info
on using an audio transformer for voltage injection, also on the use of
current injection. Added explanations to unclear areas.
zerohng2.pdf Updated October 5, 2004
The revised and corrected "zero force" hinge. A design for a vertical
seismometer beam hinge having extremely low restoring force.
bbab-028.pdf Updated November 13,
1998 - 109k
Burr-Brown Corporation Application Bulletin 28 - "Feedback plots define
op-amp performance" This was written for operational amplifier designers,
but is an excellent tutorial on all aspects of feedback design. Downloaded from
the old Burr-Brown Web site.
bbab-045.pdf Updated November
13, 1998 - 73k
Burr-Brown Corporation Application Bulletin 45 - "Op-amp performance
analysis" Another excellent article for op-amp designers that contains
much wisdom about feedback systems in general.
vertgeom.pdf Updated October 5, 2004
Comparison of the geometries of the LaCoste infinite-period vertical
sensor design and a leaf spring vertical such as the STM-8. Includes graphs
demonstrating infinite-period behavior. When complete, I hope to
also include some procedures to derive the physical design for an infinite-period
leaf spring vertical.
vertgeom.dxf Updated February 19,
1999 - 154k
CAD file of vertical seismo geometry. Used to make two images
in the above doc file. (Use scale of 2.5" per inch.)
spring2.pdf Updated October 5,
2004 - 60k
Previously updated to correct error in "Maximum Stress " values, also
corrected one formula. This is the result of a spreadsheet analysis
of a strongly bent flat spring as used in the STM-8 vertical seismograph.
It contains data and graphs of the force-deflection curves of a 12"x3.5"x0.018"
spring and measured data on a 0.5"-wide spring as a test of the theory.
Included is a discussion of the equations, which were derived from a section
in reddick.pdf .
spring.txt Updated October 27,
1998 - 83k
For those who would like to re-create the spreadsheet analysis, this
is a tab-delimited text file which should import successfully into most
any spreadsheet program. Column widths and number formats will have
to be re-entered, but all formulas are included. Includes a short
table of elliptic integrals which are required for the computation.
Results are in both pounds/inches and Newtons/meters.
October 23, 1998 - 169k
Three pages scanned from Reddick & Miller "Advanced Mathematics
for Engineers" - 2nd edition, New York, John Wiley and Sons, 1938
This is a (rather challenging) mathematical analysis of the curve taken
by flat springs when loaded at the ends via hinges, known as the Elastica.
The results of this article were used to derive the formulas for computing
force vs length for the STM-8 vertical seismometer spring in spring.pdf
October 5, 2004 - 24k
A short analysis of the temperature coefficient of the STM-8 leaf spring.
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Versions available for most computer systems.
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