Force Balance Vertical Seismometers

[g...@theconnection.com]

Hi Everyone,

I see a lot of discussion about the Raspberry Shake seismometers, how are they with the far distance shakes coming from the South Pacific. Are there any members with a Force Balance Vertical unit that Brett Nordgren and Dave Nelson developed several years ago. I have a couple, one a vertical and also a horizontal see: https://www.theconnection.com/  It would be good to compare notes on our FBV’s.

Take Care,

Gary

 

 

 

585 Lincoln Ave.
Palo Alto CA 94301

650-326-0655

 

Check Out Latest Seismometer Reading

 

I hear and I forget. I see and I remember. I do and I understand. Chinese proverb

 

Be Like Costco…do something in a different way

 

Don’t trust Atoms…they make up everything

 

Fortune Favors The Brave

A part of good science is to see what everyone else can  see but

    think what no one else has ever said.

The difference between being very smart and very foolish is

    often very small.

So many problems occur when people fail to be obedient when

    they are supposed to be obedient, and fail to be creative when

    they are supposed to be creative.

The secret to doing good research is always to be a little

    underemployed. You waste years by not being able to waste

    hours.

It is sometimes easier to make the world a better place than to

    prove you have made the world a better place.

                               Amos Tversky

 

 

[Pete Rowe]

Hi Gary

I have a Yuma2 running in Los Altos. 

My friend, Alan George, also built one. His is at his son's house in San Diego. 

Go to www.rowelabs.com. 

Push the seismometer button. You will see seismograms from each of us.

We have two filter setting so we see teleseisms and local quakes.

I haven't been on the psn list in a long time. I was one of the early PSN geeks.

Come visit me sometime. 

Pete Rowe

Pete...@rowelabs.com 

Yahoo Mail: Search, Organize, Conquer

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[Bob Hammond]

Gary,

Here's some screen shots of the Molucca Sea event (2026-04-01 22:48:12 UPDATED: (M7.4) Molucca Sea 1.2 126.3) for a Raspberry Shake in Mullan ID, my MOHO Pro, and my Guralp CMG-40 T 1-second instruments.  I am absolutely sold on the MOHO.

Bob

Top trace in WinQuake is the Guralp CMG-40T 1-second instrument.  Bottom trace is the MOHO Pro.  They are running side by side.

--

[Bob Hammond]

My installation:

Moho Pro:

[Robert Beer]

Gary,  et al.,

I built a couple of the Yume-2 seismometers that are running in Bluffton, Ohio.  I am attaching screenshots of the event.  The first is one of the Yuma's and the second is a national array seismometer in Columbus Grove, Ohio.  I am using the Terrashark 3-channel 24-bit A/D from Angel Rodriguez on a Beaglebone Black.  The data is from Earthworm and the LLZ channel is decimated (DecimationRates    "5 4").  Both are plotted with Philip Crotwell's seisplotjs Javascript package, https://github.com/crotwell/seisplotjs.  I wrote the Javascript web app running on the Beaglebone  SBC.

Comments and questions are welcomed.

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Bob Beer <r-be...@onu.edu>

[g...@theconnection.com]

Nice work Bob. To keep out the atmospheric noise, I tried 3 methods, first was a simple Styrofoam box, still noisy, next was a ¼” thick Plexiglas sealed box, still noisy. Finally I ended up with ½” sealed steel case, now very quiet. It takes learning to do this. Are the Raspberry Shake units sealed from the atmosphere?

Take Care,

Gary

 

 

 

From: psn...@googlegroups.com <psn...@googlegroups.com> On Behalf Of Bob Hammond
Sent: Saturday, April 4, 2026 5:28 AM
To: psn...@googlegroups.com
Subject: Re: [PsnList] Force Balance Vertical Seismometers

 

My installation:

 

 

Moho Pro:

 

On Sat, Apr 4, 2026 at 5:19 AM Bob Hammond <propg...@gmail.com> wrote:

Gary,

 

Here's some screen shots of the Molucca Sea event (2026-04-01 22:48:12 UPDATED: (M7.4) Molucca Sea 1.2 126.3) for a Raspberry Shake in Mullan ID, my MOHO Pro, and my Guralp CMG-40 T 1-second instruments.  I am absolutely sold on the MOHO.

 

Bob

 

 

 

 

To view this discussion visit https://groups.google.com/d/msgid/psnlist/CAKoB7Oqt0cw_udx_CVDo0YKE5UFcwTbgs92KmJ2K-BhkDy2sAQ%40mail.gmail.com.

[Brian Kuschak]

I’m still running two Yuma-2 FVBs in Washington and Oregon.  

Haven’t updated my page in years and some details are out of date now, but the data plots are live:
https://www.groundmotion.org/

One of the FBV was deployed to a quiet remote site:
https://sites.google.com/view/personal-projects-brian/home/seismic-station-deployment

I’d like to build a MOHO Pro at some point.

Brian

To view this discussion visit https://groups.google.com/d/msgid/psnlist/CAA3252cfAWtKvxnOe%2BaCC9Z8PWp83q_zZXhfuYSR2jEoisWjKw%40mail.gmail.com.

[Bob Hammond]

Gary,  what you don't see inside the foam box is a sealed industrial polystyrene case.  I don't have a photo of it right now.  I agree, a sealed steel or thick aluminum case would be better.  More mass too which helps.

The Raspberry Shakes are not sealed.  The plot I sent is from a RS located on the floor of a fire station near an active mine and I'm surprised how well it does.  I don't like how expensive it is to get data from the RS but that's their business model.

This is a good alternative to the RS:  https://github.com/erellaz/seisberry

Bob

To view this discussion visit https://groups.google.com/d/msgid/psnlist/1cbb01dcc47d%24681bf110%243853d330%24%40theconnection.com.

[Brendan Cooney]

Hi Gary

do you or does anybody else have any construction details of the INYO or YUMA force balanced seismographs, i noticed that some of the links on Larrys website are not working. I'm based in the south east of ireland and its fairy quite seismically.  Plans, BoM, Dimensions, coil construction etc etc would be great.

regards

Brendan.

--

[Bob Hammond]

Here's what I have:

https://www.groundmotion.org/main.html

To view this discussion visit https://groups.google.com/d/msgid/psnlist/9bab7c95-d84b-4fb4-9c93-3afb8367dd83%40gmail.com.

[Angel Rodriguez]

Hi Brenden,

The CAD files, BoM might be available and I will take a look at the end of this month.  So much was lost when Brett passed away.  Today most of Dave's and my energy is in the MOHO Pro which is 3D printed and almost as good as the metal variaants.  The print files and BoM for those are available as well as kit with essential items that might hard to get. Making the springs is one of the hard parts.

Cheers,

Angel

To view this discussion visit https://groups.google.com/d/msgid/psnlist/9bab7c95-d84b-4fb4-9c93-3afb8367dd83%40gmail.com.

[John L. Males]

Brendan,

Bob Hammond's reply of Brian's site of
<http://www.groundmotion.org/main.html> if an excellent resource
for many elements of a Yuma2 build that at least has the
schematic, mechanical drawing and parts list. Much of the
information would apply to building a Inyo. Also excellent set of
information in addition to helicorder for Yuma2 recording.

Some other links for Inyo built that have active helicorders as
well are:

<https://www.buffalogeo.com/Inyo.html>
<https://www.buffalogeo.com/Inyodetails.html>
<https://www.buffalogeo.com/florenceseismic.html>

<https://www.theconnection.com/design-details-for-fbv/>
<https://www.theconnection.com/fbv-steel-case/>
<https://www.theconnection.com/force-balanced-vertical-seismometer/>

<https://www.sydneystormcity.com/g_phones.htm#INYO>
<https://www.sydneystormcity.com/seismograms.htm>

Inyo that was active many years until about mid 2024:

<http://web.archive.org/web/20200117153249/http://earthalabama.com/equipment.html#Inyo_parts>
<http://web.archive.org/web/20200217013731/http://earthalabama.com/seismicity.html>
<http://web.archive.org/web/20240822135236/http://earthalabama.com/seismicity.html>

Other Yuma2 built about 10 years ago with only helicorders of the
instruments and still active are:

<http://alanslab.com/seismo/seismo.html>
<http://www.rowelabs.com/roweseismo.html>

Alan has few pics of his Yuma2:

<http://www.alanslab.com/Yuma/Yuma.htm>

There was an excellent site of Yuma2 build and smaller Yuma2 builds
that sadly for all intents archive.org did not archive what was
simple HTML web site and images of <http://www.earthmode.org>. A
really great loss. I might, but have not been able to find yet
copies in PDFs and HTML manual saves of <http://www.earthmode.org>.

The resource that is one link I am sure you have seen for all files
and related information for building and theory for Inyo and Yuma2
for many years was Brett M. Nordgren's web site
<http://bnordgren.org/seismo/>. Again sadly archive.org for all
intents did not archive over the many years for all intents
<http://bnordgren.org/seismo/> so when bnordgren.org domain expired
a few months after Brett passed away
<https://www.legacy.com/us/obituaries/name/brett-nordgren-obituary?id=54163943>
the site was lost except at least I made copy of site a few days
prior to bnordgren.org domain about to expire and a few times in
few years prior for other reasons.

Trying to figure out from files on <http://bnordgren.org/seismo/>
the information to build an Inyo or Yuma2 is challenge. I started
working on building document in LibreOffice start of 2025 to
consolidate, organize, with table contents link index and internal
links to cross reference the related information including
information that applies to both instruments or very close to
same. This is a very time consuming effort that sadly paused
unexpectedly mid 2025 where I have multiple OS issues. No data loss
for work, just pause I man itching to resume. The effort is very
time consuming as I have to convert each PDF manually for
LibreOffice as only way to correctly convert. PDF conversion tools
make a mess and not even close to conversion I do manually. One
PDF takes from day to over week to convert. The various advanced
math formulas take alot of effort to convert and ensure I converted
manually correctly. I do make various comments, additions, et al
of my own at times in document. The document has credits of
designers, builders (I have included details of builder's
information for their instruments, et al).

I have no mill or such equipment. I really wanted to build some
Inyos. In late 2023 I tried to make Boom1 which is most
challenging Inyo part to made with just hand hacksaw and file. I
managed to make a Boom1 and managed to achieve the important
tolerance and parallel cut of the hinge part of Boom1. I
managed to achieve a tolerance for the Boom1 hinge of +- 0.005"
with freehand hacksaw, file, and unique technique of hand taped
guides on the raw Boom1 L before I started to cut with hacksaw.
This took nearly 30 man hours over about 6 weeks due to weather:

<https://www.flickr.com/photos/33969106@N03/54531839860>
<https://www.flickr.com/photos/33969106@N03/54530615037>
<https://www.flickr.com/photos/33969106@N03/54530615042>
<https://www.flickr.com/photos/33969106@N03/54531734408>

I have no workshop so all this metal work has to be done outside
during non-winter months.

I had actually wanted to build an Inyo for years, but I did not
feel I could make Boom1. As side note if you look carefully at
<https://www.buffalogeo.com/Inyodetails.html> you will see a
different approach to buildin the Inyo Boom where the L is actually
a seperate piece of metal attached via machine screws and a one
piece boom rater than larce Boom1 with small L attached to Boom1 to
connect to boom capacitor plates.

When I saw how parts for Yuma2 were laid out on
<http://www.earthmode.org> and
<http://earthalabama.com/equipment.html#Inyo_parts>
mid 2019 I started to find tapping, micrometer, and other items
needed before I start purchasing metal. Sadly mid Fall 2019 I
sustained a very serious rib cage injury that made normal
breathing very very painful, let alone near impossible to sleep,
get in/out bed, make meals, no showering for months, etc. By time
the rib cage injury was bearable early March 2020 COVID-19 changed
the most basic for everyone. It was not until Fall 2023 could I
purchase any metal from any metal store in Toronto as these metal
stores (not same company) continued to operate in COVID-19
lock down when for over 2 years, and only few times mild
variations until 18+ months prior to metal stores deciding to stop
COVID-19 lock down. I purchase in person and pay cash as done for
years at metal stores where I can usually find what I need in
offcuts so no need to cut from standard stock. Hence a 4+ year
delay in starting my Inyo and Yuma2 building.

I learned and designed 3D print file for Yuma2 coil and then over
next few years improved code so can make coil form using same
OpenSCAD file just using different basic dimension information.
Using this same OpenSCAD file with different basic dimension
information I can create coil jibs to centre magnet in ring and
align boom to level with coil centred to coil. This in my opinion
will require different ring height, and changes to some of magnet
assembly materials used. After I have built an Inyo and Yuma2 with
ring magnet assembly I will try an alternate coil/magnet design I
arrived at in later 2019 easier to make with other pluses in
design. I have tested the design idea, hence know should work with
Inyo and Yuma2.

In 2024 I managed to cut most of metal for 3+ Inyos and 4+ Yuma2.

A key electronic part for the electronics, Wima MKS2 10uF, was
end of life Spring 2025 because the company that supplied the
unique very thin film used for MKS2 stopped production on short
notice due to financial problems. This means the ExpressPCB
files for the Inyo and Yuma2 are no longer useable because the
MKS2 uF was unique in only 10uF film capacitor with 5mmpin
spacing. Most 10uFs are 22mm or larger pin spacing with one
exception of one made at 15mm pin spacing. Hence new PCB needs
to be designed to accommodate the larger PCB space six 10uFs will
require. It will not be good idea to use MLCC for these six 10uF
film capacitors.

It is likely best to design PCB using Open Source ECAD so PCB can
be made by any PCB fab but ExpressPCB. ExpressPCB will not accept
gerber files and no other PCB fab can use ExpressPCB files. The
schematics were on Brett's site in PDF as well as the ExpressPCB
files.

I am still trying to find hoe for files on
<http://bnordgren.org/seismo/> and of course would post WIP
organized consolidation PDF and LibreOffice document that takes just
couple clicks over few seconds to create PDF with PDF links. I was
really hoping to do so with bnordgren.org domain, but bnordgren.org
domain keeps bouncing about to other parties using bnordgren.org
for really odd makes no sense uses. I wanted to use bnordgren.org
as many links many places refer to bnordgren.org or files of
bnordgren.org. The other goal is once have site, ideally
bnordgren.org fine way for archive.org to correctly archive again
ideally with bnordgren.org. Maybe trying to hold out for
bnordgren.org is not best practical approach.

I also like to find new home for fbv-topics mailing list using same
mailing list software that fbv-topics uses. So far only can find
paid versions of sites specifically designed to host just mailing
lists using same software. Easy to import existing fbv-topics. I
have sense with Brett's passing there is not anyone else to
approve new persons wanting to join fbv-topics that has good
information on the Inyo and Yuma2 that still apply.


John L. Males
Toronto, Ontario
Canada

2026-04-12 10:38+0000 UTC eMail Start
2026-04-12 12:47+0000 UTC
2026-04-12 08:47-0400 EDT

*****Not GPG/PG Signed*****



On Date: Sat, 11 Apr 2026 10:25:02 +0100
From: Brendan Cooney <brenw...@gmail.com>

To: psn...@googlegroups.com
Subject: Re: [PsnList] Force Balance Vertical Seismometers

> Hi Gary
>
> do you or does anybody else have any construction details of the
> INYO or YUMA force balanced seismographs, i noticed that some of
> the links on Larrys website are not working. I'm based in the
> south east of ireland and its fairy quite seismically.  Plans,
> BoM, Dimensions, coil construction etc etc would be great.
>
>
> regards
>
> Brendan.
>
> On 03/04/2026 22:39, g...@theconnection.com wrote:
> >
> > Hi Everyone,
> >
> > I see a lot of discussion about the Raspberry Shake
> > seismometers, how are they with the far distance shakes coming
> > from the South Pacific. Are there any members with a Force
> > Balance Vertical unit that Brett Nordgren and Dave Nelson
> > developed several years ago. I have a couple, one a vertical
> > and also a horizontal see: https://www.theconnection.com/ It
> > would be good to compare notes on our FBV’s.
> >
> > Take Care,
> >
> > Gary
> >

> > *585 Lincoln Ave.
> > Palo Alto CA 94301*
> >
> > *650-326-0655*
> >
> > **
> >
> > Check Out Latest Seismometer Reading <http://theconnection.com/>
> >
> > *I hear and I forget. I see and I remember. I do and I
> > understand*. Chinese proverb
> >
> > __
> >
> > *Be Like Costco…do something in a different way*
> >
> > *Don’t trust Atoms…they make up everything*

> >
> > Fortune Favors The Brave
> >
> > A part of good science is to see what everyone else can  see but
> >
> > think what no one else has ever said.
> >
> > The difference between being very smart and very foolish is
> >
> > often very small.
> >
> > So many problems occur when people fail to be obedient when
> >
> > they are supposed to be obedient, and fail to be creative when
> >
> > they are supposed to be creative.
> >
> > The secret to doing good research is always to be a little
> >
> > underemployed. You waste years by not being able to waste
> >
> > hours.
> >
> > It is sometimes easier to make the world a better place than to
> >
> > prove you have made the world a better place.
> >
> > Amos Tversky
> >
> > --
> > You received this message because you are subscribed to the
> > Google Groups "Public Seismic Network Mailing List" group.
> > To unsubscribe from this group and stop receiving emails from
> > it, send an email to psnlist+u...@googlegroups.com.
> > To view this discussion visit
> > https://groups.google.com/d/msgid/psnlist/1bb501dcc3b2%246a9cfae0%243fd6f0a0%24%40theconnection.com

> > <https://groups.google.com/d/msgid/psnlist/1bb501dcc3b2%246a9cfae0%243fd6f0a0%24%40theconnection.com?utm_medium=email&utm_source=footer>.

>
> --
> You received this message because you are subscribed to the
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> send an email to psnlist+u...@googlegroups.com. To view
> this discussion visit

> https://groups.google.com/d/msgid/psnlist/9bab7c95-d84b-4fb4-9c93-3afb8367dd83%40gmail.com.

[g...@theconnection.com]

Hi Brendan,

Others have replied I see. I did a lot of experimenting in order to find the right box to keep out atmospheric noise. Ended up with 1/2 inch steel container. Nice and quiet now.

Gary

 

 

 

From: psn...@googlegroups.com <psn...@googlegroups.com> On Behalf Of Brendan Cooney
Sent: Saturday, April 11, 2026 2:25 AM
To: psn...@googlegroups.com
Subject: Re: [PsnList] Force Balance Vertical Seismometers

 

Hi Gary

To view this discussion visit https://groups.google.com/d/msgid/psnlist/9bab7c95-d84b-4fb4-9c93-3afb8367dd83%40gmail.com.

[michael k]

Hi Gang,

Long time lurker here due to life responsibilities.  I have a mechanically complete Yuma that I finished about 7 years ago (there is probably a post of mine in the PSNlist with a pic.)  My goal for 2026 is to finally finish the electrical board and get it up and running.  Fingers crossed.

I did pull some of Brett's files years ago, specifically about the Yuma.  I have posted them on my site if anyone cares to take a look.  If others have additional files from Brett's site, I'm happy to add them.

mckimzey.com/seismic/yuma/

Regards,

Mike

[John L. Males]

Michael,

Do you have 6 of the Wima MSK2 10uF capacitors needed for Ci nd Cd?
I ask on assumption You have either a V2.0 or V4.x PCB. Wima had to
EOL the MKS2 (and believe MKS02) on short notice from supplier of
very unique thin film used due to supplier financial challenges. I
would not suggest using ceramic parts in place of Ci and Cd.

There are few sources left, but they are charging about 10 time
original cost these sellers pain for these MKS2 10uF.

One of my ToDos is create new PCB via KiCAD to use 10Uf film
capacitors with 15 or next pin spacing up I think is 22mm or 27mm.

If you have not populated your Yuma PCB yet I suggest not
populating:

1) C9 big time with reason being causes significant different
response difference between High and Low outputs not just for top
end slope, but for time constant of output. There is no integrator
capacitor for Low output. Ci is where integration is. I have lots
of proof from operational Inyos and Yuma2s of the significant
difference in response of High and Low outputs that is not related
to 50X gain of High output with C9 present.

2) C10 as not needed for inverse filter as C10 is not part of
inverse filter formula. C10 adds integration not needed in my
opinion and exaggerates the Ci integration in my opinion.

3) C14 adds unnecessary exaggerated integration to Ci
integration.

4) C13 again adds unnecessary integration like C9 and there is no
integration capacitor for Centre Force.

5) C11 in my opinion adds unnecessary exaggerated integration to
Ci.

6) C25 change from 0.1uF to 0.01uF to match all other outputs using
100R0/0.01uF as output.

If you were to open the original Loop7Y.xls and set these noted
capacitor vales to zero in "Control" tab (C11 occurs twice in
"Control" tab) then open a second copy of same original
Loop7Y.xls. Select the "Instrument" tab for both opened versions
of Loop7Y where you will observe major difference in "Instrument"
response. The version with noted capacitors set to zero is
better and top end roll off is actually symmetrical as should be
for High and Low high end as the Top end and Low end curves are
same slope due to

I really like the Organized directory you decided on. I was going
to do similar, but change file names to add to organization.

I have a few complete snapshots of Brett's website. A few that are
likely the same month or two before Brett's site went dark. One
copy a day or so before went dark. One or two a few years prior to
site gone dark that has more files (about twice file space).

I have wanted to find home for the files. I have been holding out
for bnordgren.org domain to be available and reasonable cost as
there were many references on internet pointing to that cannot be
changed with one or two exceptions I know of.

I managed via some creative technical skills have some files via
archive.org that may be better or files I was not aware existed.

The file name approach I am still working on would be along lines I
was using for document where I am consolidating all files into
organized links table contents and intra-linked in PDF document
cross references via LibreOffice document still WIP.

I have made added versions of some of Brett's files, with more
likely. That said my intent is to add to not replace original file
by Brett.

I have also been working on improved Loop7 spreadsheet four
Yuma2 where one can read formulas as math formulas rather than hard
coded cell references. In process I discovered a few errors in
Loop7 spreadsheet due to simple typos in cell references. I have
not completed yet. After I need to repeat from scratch the Loop7I
for Inyo. Then maybe Napa Loop7N where maybe is because no
mechanical plans were published for Napa, but excellent pics were
with ruler maybe mechanical can be deduced.

For adding files to your site I could feed them to you a bit at
time and suggested directory for.

John L. Males
Toronto, Ontario
Canada

2026-04-21 02:21+0000 UTC eMail Start
2026-04-21 03:43+0000 UTC
2026-04-20 23:43-0400 EDT

*****Not GPG/PG Signed*****



On Date: Mon, 20 Apr 2026 17:10:39 -0700 (PDT)
From: michael k <mcki...@gmail.com>
To: Public Seismic Network Mailing List <psn...@googlegroups.com>
Subject: [PsnList] Re: Force Balance Vertical Seismometers



> mckimzey.com/seismic/yuma/

[Brendan Cooney]

Hi Mike

That is brilliant!! I have 2 documents I downloaded and i don't see them on you site. 

I'm cc'ing your email as i don't know if the list address allows file attachments so they should get to you.

I'm downloading the files you have as they'll help me in my build.

Regards

Brendan.

--

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[John L. Males]

Brendan,

The "FBV_Circuit_Description.pdf" shows the Inyo schematic where
key elements are same as the later versions of circuit such as
Yuma, Napa. I have on my ToDo list to extend for later schematics
where the major difference is the design of analogue output after
the Inverse Filter ignoring a set of part values that are
different. The idea is will still

There are two documents:

"Inyo_FBV_history.pdf" created 20111113 Document Undated
"FBV_Overview.pdf" created 20121031 Document Dated 20230502

The "Inyo_FBV_history.pdf" is single page document with mostly
similar to page 1 of "FBV_Overview.pdf".

Michael,

My suggestion for files Brendan attached is
"FBV_Circuit_Description.pdf" be in directory called "Theory" or
"Design" not in directory of ant Instrument. as there will be other
files that will make sense for such a directory.

"FBV_Overview.pdf" I suggest likely makes sense to be in base
directory of directory your directory set up as applies to all
Instruments. An "All" or "Any" directory in some ways might make
sense, but if I recall there would be only 1-3 documents for such
a directory. I am inclined makes sense such documents be in base
directory. If my memory is correct I used "Introduction" and/or
"History" for table of contents for such documents in the
consolidation document WIP I will resume once some OS matters are
sorted out.

The consolidated document is in range of about 400 pages and about
150Mb thus far. Test in conversion takes up little space. The
bulk of the document size is converting various schematic versions,
many different mechanical drawings, graphics in PDFs, pics of
instrument builds, key builder web site images (with related text),
et al. The page count as one example due to many pages the
drawings consume and the well over hundred pages of text from
PSNList archive for Sean-Thomas Morrissey that took several days to
reformat the well over hundred pages to be correct looking as
originally due to many ASCII diagrams of Sean-Thomas Morrissey.
The archive of Sean-Thomas Morrissey was included because of key
references to Sean-Thomas Morrissey and related PSNList
items/archive by Brett in some of Brett's documents.

To be clear the suggestions for directory as just that only
suggestions.

When I have chance to copy the files on the consolidation work I
started early 2025 that paused late Spring 2025 due to multiple OS
issues it will be easy to see from how I have organized files. The
rational I used to organize files in document lists original source
of file, including zip file name were is case, and/or file dates
and/or PDF create date, and/or date in actual document. I can tell
you I struggled for some time how to organize files in the
consolidation work I have done thus far. I am hoping I have what
make sense in how I organized files in the consolidation work I am
doing and fear if not then I know from first few initial attempts I
will have alot of work to organize again. Hence my suggestions for
directory names are just that, only suggestions.

John L. Males
Toronto, Ontario
Canada

2026-04-21 12:48+0000 UTC eMail Start
2026-04-21 13:59+0000 UTC
2026-04-21 09:59-0400 EDT

*****Not GPG/PG Signed*****



On Date: Tue, 21 Apr 2026 13:24:05 +0100
From: Brendan Cooney <brenw...@gmail.com>
To: psn...@googlegroups.com, mcki...@gmail.com
Subject: Re: [PsnList] Re: Force Balance Vertical Seismometers

> > *585 Lincoln Ave.
> > Palo Alto CA 94301*
> >
> > *650-326-0655 <tel:(650)%20326-0655>*
> >
> > **

> >
> > Check Out Latest Seismometer Reading

> > <http://theconnection.com/>
> >
> > *I hear and I forget. I see and I remember. I do and I
> > understand*. Chinese proverb
> >
> > __
> >

> > *Be Like Costco…do something in a different way*
> >
> > *Don’t trust Atoms…they make up everything*

> >
> > Fortune Favors The Brave
> >
> > A part of good science is to see what everyone else can see
> > but
> >
> > think what no one else has ever said.
> >
> > The difference between being very smart and very foolish is
> >
> > often very small.
> >
> > So many problems occur when people fail to be obedient when
> >
> > they are supposed to be obedient, and fail to be creative
> > when
> >
> > they are supposed to be creative.
> >
> > The secret to doing good research is always to be a little
> >
> > underemployed. You waste years by not being able to waste
> >
> > hours.
> >
> > It is sometimes easier to make the world a better place
> > than to
> >
> > prove you have made the world a better place.
> >
> > Amos Tversky
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[Brendan Cooney]

Thanks John for update. I was looking for Sean-Thomas's uploads a few
days back and by trawling around a bit I found that his pages on the Uni
he worked for are still live.
https://www.eas.slu.edu/People/STMorrissey/index.html.


regards

Brendan

On 21/04/2026 14:59, 'John L. Males' via Public Seismic Network Mailing

[John L. Males]

Michael,

Some additional considerations for Yuma2 electronic parts.

1) Change C3/C4 to 0.0022uf from parts list and schematic value of
0.0047uF. As side note C3/C4 need to be same value, no matter
value used for C3/C4. The LTC1043 data sheet does not provide any
guidance for selecting the C3/C4 like values. I been unable to find
via web research any such guidance for the C3/C4 like values other
than comment of one post found via extensive web searching tp one
figure that uses 0.0047uF with no indication of why 0.0047uF was
used in figure of LTC1043 data sheet. The 0.0022uF was suggested by
Brett on fbv-topics twice a tad over year apart based on smalle
size of mass position sensor of Yuma2 compared to Inyo where Brett
then posted schematic 2.03 to so reflect. Why the change back for
C3/C4 for 4.x et al schematics I am not sure if on purpose,
oversight, none of, or combination. At least one Yuma2 builder,
Alan George, used 0.0022 uF for C3/C4 you can see operational
helicorder <http://alanslab.com/seismo/seismo.html>. It is not
known, but possible Pete Rowe may have also used 0.0022uf as Alan
and Pete built their Yuma2s about same time. Pete does not have
notes nor pic via Brett's website to confirm whereas by chance pic
of Alan's Yuma2 on Brett's site happen to show C3/C4 0.0022uF was
used i never noticed until Fall 2025. I had looked at this Yuma2
pic of Alan's many times over last few years due to unique boom
counter weight approach I suspect why I never noticed C3/C4 was
0.0022uF. The MOHO Pro Bob Hammond has where circuit was provided
already soldered
<https://groups.google.com/g/psnlist/c/dDK13Xl_ymQ> re
<https://11056767104761328006.googlegroups.com/attach/69ece5b347f5e/Moho.JPG?part=0.1&view=1&vt=ANaJVrEJKA2T2i6HlVYUpp3kpb8vKck7uE60gaW3O0ZEBTykaut7V2q5NQUSk5MPvyWsxX1zJKHqWr8fw66hmvdm9apfMv99uvXSqS5hBsbKAH0g4zmIogw>
uses 0.0039uF for C3/C4. The MOHO/MOHO Pro mass position sensor I
estimate to be larger than Inyo. Based on my MOHO/MOHO Pro
estimate that would suggest C3/C4 for Yuma2 of about 0.0015uF for
Yuma2 based on ratio of Yuma2/MOHO Pro mass position ratios. I am
not sure if makes sense to use 0.0015uF for Yuma2 C3/C4, but at
least known 0.0022uF works well for Yuma2 based on 10+ years of
Yuma2 operation of Alan's Yuma2.


2) When I set the noted capacitors in Loop7Y to zero there was a
small peak at top end of instrument curve. I found when I reduced
the coil resistance from 44 ohms to 38 ohms the peak disappeared.
The Yuma2 coil is specified as AWG #34 for about 550 turns. Math
suggests based on ratio of 38/44 closest from resistance reference
is AWG #33. I suspect AWG #33 would be difficult to have to order
custom (huge cost and MOQ) not an option. Next AWG #32 easy to
obtain and if used math suggests about 750 turns likely to need
weaker than N45 magnet where next tier down is N40 or N35 in order
to likely still result in GN for Yuma2 design. Math suggests
using Yuma2 specified AWG #34 that reducing turns to 475 likely
will be close to 38 ohms for coil that again will change GN likely
needed bit stronger magnet, maybe N50. The top end peak is not that
significant so likely staying with about 550 turns of AWG #34 will
be fine. I mentioned so you aware there will be slight top end peak
in response when do not populate as I noted capacitors and how peak
was eliminated.

John L. Males
Toronto, Ontario
Canada

2026-04-21 14:47+0000 UTC eMail Start
2026-04-21 15:51+0000 UTC
2026-04-21 11:51-0400 EDT

*****Not GPG/PG Signed*****



On Date: Tue, 21 Apr 2026 03:43:11 +0000
From: "John L. Males" <sei...@softhome.ca>
To: michael k <psn...@googlegroups.com>
Subject: Re: [PsnList] Re: Force Balance Vertical Seismometers

[John L. Males]

Brendan,

Yes, Sean's web site link you noted is still alive. At some point
the university will remove. This has occurred with well used web
pages of UK professor where at least in their case they archived it
completely to github code and web pages that others have used to
restore so people can continue to use the filter calculators.

A site that documented well a build based on Sean's design is
<http://bryantlabs.net/VertSeis.html>

The archive I was referring to Brett makes reference to in
"FBVsolve01.pdf" is:

Bibliography:

1 Wielandt, E. & Streckeisen, G., 1982.
The leaf-spring seismometer: design and performance, Bull. Seism.
Soc. Am., 72(6), 2349-2367.

2 Morrissey, S.-T., 26 Mar 2000
Correspondence archived on Public Seismic Network
http://psn.quake.net/info/stm-mail.zip
http://www.eas.slu.edu/People/STMorrissey/index.html


It is the <http://psn.quake.net/info/stm-mail.zip> that took me
many days to reformat to have same look as in ASCII in the
LibreOffice document consolidating of Brett's files and take up
100-200 pages of the 400+ page so far document. The text of
<http://psn.quake.net/info/stm-mail.zip> takes up little space of
currently about 150MB consolidated PDF document as just text.

John L. Males
Toronto, Ontario
Canada

2026-04-21 16:22+0000 UTC eMail Start
2026-04-21 16:37+0000 UTC
2026-04-21 12:37-0400 EDT

*****Not GPG/PG Signed*****



On Date: Tue, 21 Apr 2026 16:47:49 +0100

From: Brendan Cooney <brenw...@gmail.com>
To: psn...@googlegroups.com

> https://groups.google.com/d/msgid/psnlist/15b9324a-eadc-44b0-814f-6caa8885d3f2%40gmail.com.

[John L. Males]

Brendan,
Michael,

Opps I just discovered a typo for:

"Inyo_FBV_history.pdf" created 20111113 Document Undated
"FBV_Overview.pdf" created 20121031 Document Dated 20230502

I made serious typos to both dates of "FBV_Overview.pdf" with
correction that follows:

"Inyo_FBV_history.pdf" created 20111113 Document Undated

"FBV_Overview.pdf" created 20131031 Document Dated 20130502

Sorry.

John L. Males
Toronto, Ontario
Canada

2026-04-21 17:36+0000 UTC eMail Start
2026-04-21 17:43+0000 UTC
2026-04-21 13:43-0400 EDT

*****Not GPG/PG Signed*****



On Date: Tue, 21 Apr 2026 13:59:08 +0000

From: "John L. Males" <sei...@softhome.ca>

To: Brendan Cooney <psn...@googlegroups.com>, michael k
<psn...@googlegroups.com> Subject: Re: [PsnList] Re: Force Balance