
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 rightclick.
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
changes.)

sts1solve.zip Updated October 5, 2004
 622k
An analysis of a fixedend astatic leaf spring vertical seismometer,
using the STS1 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
 9k
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 STM8 loop.
Part II of a series.

loop3.pdf Updated
November 28, 1998  91k
This is an ongoing mathematical analysis of the feedback loop properties
of a forcefeedback seismograph. Part III of a series.
STM8 block diagram and definitions of the blocks. Both forward
and feedback paths analyzed and results graphed along with loopgain and
response curves for velocity input only. Includes asymptote and cornerfrequency
formulas and evaluation of how some individual components are affecting
the system. Matches ST 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 STM8 driver circuit and P/I/D branches
in order to improve DC stability and resistance to spring creep and other
slowlyvarying forces. Incorporates suggestions received from several
sources on the previously proposed design modifications. Addendum
added to address noise issues raised by ST Morrissey.

lpmeas2.pdf
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
 35k
The revised and corrected "zero force" hinge. A design for a vertical
seismometer beam hinge having extremely low restoring force.

bbab028.pdf Updated November 13,
1998  109k
BurrBrown Corporation Application Bulletin 28  "Feedback plots define
opamp performance" This was written for operational amplifier designers,
but is an excellent tutorial on all aspects of feedback design. Downloaded from
the old BurrBrown Web site.

bbab045.pdf Updated November
13, 1998  73k
BurrBrown Corporation Application Bulletin 45  "Opamp performance
analysis" Another excellent article for opamp designers that contains
much wisdom about feedback systems in general.

vertgeom.pdf Updated October 5, 2004
 141k
Comparison of the geometries of the LaCoste infiniteperiod vertical
sensor design and a leaf spring vertical such as the STM8. Includes graphs
demonstrating infiniteperiod behavior. When complete, I hope to
also include some procedures to derive the physical design for an infiniteperiod
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 STM8 vertical seismograph.
It contains data and graphs of the forcedeflection 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 recreate the spreadsheet analysis, this
is a tabdelimited text file which should import successfully into most
any spreadsheet program. Column widths and number formats will have
to be reentered, 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.

reddick.pdf Updated
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 STM8 vertical seismometer spring in spring.pdf
.

tempco.pdf Updated
October 5, 2004  24k
A short analysis of the temperature coefficient of the STM8 leaf spring.
If you can't view and print the .pdf files,
just download your free Adobe Acrobat Reader.
Versions available for most computer systems.
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