000529-01a
The seismometer above operates very much like a S-G type seismometer, except that there is no physical "boom", the diamagnetic graphite "floats" a neodymium magnet in a roughly directional channel within the graphite.  The large black colored object midway down from the top are actually ferrite magnets on a threaded rod, which is adjusted up or down to help adjust the height of the levitated magnet.  Like all magnetic masses, alot of problems arise because it is magnetic.  In the picture, no wires from the Hall sensor are shown.  For a practical seismometer, I would not recommend this approach, it is too expensive overall and very time consuming to achieve even a limited result, with little real useful output.....however, its "different", and therefore somewhat interesting in itself.

Thanks go to John Lahr, Charles Patton and Robert Lamb for their assistances over time in relation to this project.  John Lahr introduced me to this diamagnetic subject back in 1998, and whom maintains a steady interest.  Charles Patton introduced me to a key model machine in mid 1999, and was key to obtaining some diamagnetic bismuth material, which although it has been superceded by superior graphite since, it did substantially create a more hopeful atmosphere in obtaining better diamagnetic material.  Robert Lamb has had a long time interest in diamagnetism, and has delved alot into the details of diamagnetics, and with whom I've shared many notes and materials over quite a span of time.  Here; again, Robert Lamb's Hall sensor circuit is used in its original circuitry, and it has been very reliable.  Robert has been the source of all electronic resolutions in the Hall sensor circuits, and he has done alot of diamagnetics experiments and research on his own over many years.

Other individuals which have shared this subject of diamagnetism, and who have made large and significant contributions include Martin Simon of the UCLA Dept. of Physics and Astronomy, whose machine the essential pyrolytic Graphite has been used in this approach, and his contributions of information.  Dan Bartmann of the firm of Forcefield/Wondermagnet, has shown strong interest and has made material contributions of subject trial magnets, and one of which is described further, and is the source of the magnets used in this trial instrument.  Indeed, the magnet of choice lies solely from this source; no other known magnet is known to exist with this capability which is readily available to private individuals.

Probably in real life essence, without the help of all of the above, whether major or minor, this test instrument may never have been made.  No claim is made here as too the uniqueness of this instrument, its simply the progression of the available material, mechanical resources and present information on hand and simple experimentation.

While earlier rough models could be technically viewed as being diamagnetic pendulums or tiltmeters, with the addition of copper plates to the nearest proximity to the levitated magnet, the eddy current damping effect seems sufficient to classify this model as being more appropriately called a seismometer.  It is somewhat overdamped presently.

Simply put; the main part is the diamagnetic material used.  Here the diamagnetic disks used were those
found in Martin Simons diamagnetic machines.  The reason for this, is that this particular graphite
exhibits the strongest diamagnetic fields of any known material.  Other lesser diamagnetic graphite samples with their lesser fields have a more pronounced temperature variance from the magnets in use, and have less resulting space to allow for temperature variations, which will normally occur.  In short, the field is bigger, which allows
more space for a certain amount of temperature range, than is allowable than with a lesser material.

The second key part is the levitation magnet used.  Here, the magnet is a Forcefield magnet with the unusual magnetic orientation, of being polarized through 1/2 the diameter lengthwise, and its shape and size are such that it was readily adaptable into this machine.  It also has very useful extra gauss strength over that of a normal production neodymium magnet.

The 3rd key part is the diamagnetic graphite wedges used to simply contain the magnet within its channel.  The strength of this material need be only sufficient to exert a lateral sideways force on the magnet, and is not abosolutely necessary to be as strong as the main diamagnetic disks.  The only important dimension of this graphite is the height, which is determined by the discs graphite and the levitated magnets reaction to that.

The overhead magnet/s was the easiest obtainable item.  Here the magnets are ferrite "donuts", and are stacked
one atop another.  Ferrite magnets were chosen for one main reason over neodymium magnets.  The ferrite magnets are naturally weaker than neodymium, but in their larger mass, they do have the property of extending
the distance between them and the levitated magnet.  This is a simple pendulum effect, and can be understood by the length of a pendulum on a string.  A short string (i.e., neodymium) will have a shorter "period" of natural
oscillation, than a longer string on a pendulum.  Hopefully with a slightly longer natural period, the levitated
magnet will have less susceptibility to high frequency seismic "noise", and because of the arc of the "string" they will have more space to operate before they can touch the diamagnetic material.

The frame and base plates and leveling screws.  Here the material was simply material on hand.  Their total
weight is an asset in the sense that any adjustments have a lesser disturbance on the overall output, than if they were light weight and more flimsy construction.  Its kind of a basic sturdy frame that is a necessity in any instrument used in seismographic areas.

The sensor used.  In this case, the first sensor tried is a Hall effect device.  Here the levitated magnet has no attachments whatsoever.  Its possible to use other sensors which may require attaching other lightweight parts to the levitated magnet (optical), or, creating additional electronic parts such as may be used in various other sensors.   The Hall circuit used is a exact replica of Robert Lamb's reliable circuit used successfully on a variety of seismometers, and previously described.    Here, the Hall device only senses the movement of the levitated magnet both toward and away from the Hall device itself.  In this configuration, the sensitivity is greatly reduced, but the amplification is increased in the circuit to better evaluate the experiment.
 

000529-015a
This view shows the mechanical parts of the adjustable diamagnetic graphite plate with its Hall sensor.  Here the parts were simply glued onto the copper coated alumina plate, and after drying, they were further epoxied to insure
the parts staying thereon.  The wires are not attached to the Hall sensor socket in this view.
 

000529-016a
A closer view of the Hall sensor.  For illustration the black Radio Shack neodymium "pill" magnet is roughly centered over the Hall sensor where it would need to be for a signal.  Normally the graphite assembly is around the levitated magnet.
 

000529-018a
A side view.  For the actual seismometer the Hall leads were bent upward to where the Hall is positioned on the side of the levitated magnet, rather than underneath.  It was felt that the side position would be less subject to vertical movement readings, and temperature position changes over time.

This comes from U.S. patent 3831287, originally a borehole tiltmeter made by the Arthur D. Little, Inc., of Cambridge, Ma.  The inventors were Richard M. Sawdo and Ivan Simon.  This model was constructed by using a strong magnetic field (probably Alnico magnets),  and levitating a very lightweight hollow tube of strong diamagnetic graphite. For all purposes the graphite was tightly constrained within a linear magnetic field, and used a "flag", optical output and electromagnetic feedback to maintain the graphite centered in its range.  For a homebrew replica this design is not practical.  Temperature problems also plagued this instrument, and very few were made.  This model depended on using electronic means to center the levitated graphite.

 See: IBM Intellectual Property Network

This homebrew model basically draws from some of the same rough reversed features of the A.D. Little tiltmeter.  The graphite "sandwich" along with the earths gravity and an overhead magnets are the main parts for this experimental instrument.    For this first model, no electromagnetic influence is used, it solely depends on the magnetic pendulum effect coming from the overhead magnets, and it also has no temperature compensation arrangement; the instrument is simply enclosed in a somewhat thermally insulated box resting on a concrete pier on loose soil under a house.

The main specific graphite used, comes from the Model PGV diamagnetic levitators made at the UCLA Dept of Physics and Astronomy, by Martin Simon.  As of 3/1/2000 the U.S. price is $69.00 each.  Simply put, they represent the most diamagnetic graphite known at this time.  Moreover, the item is sold as non-profit.  Its possible to actually use this original levitator as is for this experiment, but I elected for a sturdier frame of my own.  Outside of this item, a great variety of graphite exists, but it also can vary greatly in its diamagnetic property, and some is even magnetic (paramagnetic), and nothing approaches its diamagnetic value.  I've obtained a fair variety of graphite from a number of sources, but, none have been near as diamagnetic as this material.  "Model PGV uses a more expensive pyrolytic graphite which has the highest diamagnetic susceptiblity for any solid substance (except superconductors) of about 450 x 10>(-6)", according to the reference below:

000529-001a
The above view is a part of the initial construction.  The salvaged disks are laid side to side atop the copper plate.
On the sides is the cut up "wedges", used to center the levitated magnet.
 

00529-002a
Here the top disks have been added.  This completes the graphite encirclement of the design for the levitated magnet.
 

000529-003a
Here, epoxy has been used to strengthen and hold the graphite attached to the bottom plate.
 

000529-019a
The completed graphite containment of the levitated magnet.  Here another copper plate has been glued to the top.

  SEE: DIAMAGNETIC LEVITATORS FOR SALE

The specific manufacturer of this graphite is Mineral Technologies Inc.  They actually make two varietys of pyrolytic graphite, however, unfortunately, the company can not identify which variety is the most diamagnetic.
This is in no means unusual; no graphite company makes their graphite specifically for diamagnetics and therefore their is no real interest on their part to evaluate their own graphite in this regard.  However in the
sense of using density as a measurement of purity, their SN is slightly denser being at 2.22 g/cc, (Metric units) while their CN graphite is listed at 2.19 (which appears to be the graphite of choice) .  Some writers cast the theoretical limit of graphite purity at ~2.25.  Further, actual manufacturing variations, may make these values rather useless, i.e., thickness, impurities etc; and of course no amateur experimenter is going to have a diamagnetic measurement machine on hand (k$).  Going further into the specific graphite discs, the gas disposition pyrolytic graphite is layered on top and bottom (impervious), and the usefull graphite inbetween is pervious (it can absorb liquids).  For some more details visit the web page, but, the pictures there only show the best example of pyrolytic surface (there are occasional outgassing pits, in the actual material)...not the actual cross section of the complete material as actually sold .

SEE: MINERAL TECHNOLOGIES INC.

A part of the problem of adopting graphite with a specific levitated magnet is matching or making the graphite fit the dimensions of the magnet used, with the necessary diamagnetic spacing.  In this case, the graphite discs are .7" in diameter (two joined side to side and a total of 4 discs per machine) and the magnet is slightly smaller at some 1" in length.  Its adequate with overlap of the graphite.  As I only have a variety of saws and a old drill press, one can only do with what they have.

000529-004a
This is a view of the parts underneath the overhead ferrite magnets.  Here the levitated magnet is inserted, and
physical moved to center the hall over the Hall sensor center.
 

000529-006a
Another view with the levitated magnet over the Hall.  Here the levitated magnet uses a prior shorter spacer, which was too short to allow more signal due to the levitated magnets field being much stronger than the R.S. magnet.
 

000529-010a
Another view of the levitated magnet.  The copper plates were chosen primarily for their ability to dampen the levitated magnet.  The copper is actually electrical buss bars from a surplus source.  Unfortunately, the copper
can not be adjusted for less damping as they are glued down.
 

000529-012a
This view shows the graphite/copper containment block, and the slide channel guides for adjustments in one direction on the plate.  The alumina plate has copper on both sides, but the not shown bottom has a circuit layout for a unknown application.  The alumina seems to conduct thermal heat very well; perhaps somewhat of a aid to environmental temperature changes over time.

Here, the specific magnet is from Forcefield/Wondermagnet.  This unit is some 1" in length by .250" in diameter.  The unique polarization is through half the diameter lengthwise.  The polarization means the magnet floats on its side, however their doesn't seem to be any less significant gap space from this, and indeed it could almost appear to have a slightly increased gap space when compared to a normal neodymium rod magnet.  The plating is of a thin gold over perhaps copper or nickel.   This specific magnet is indeed better in its magnetic property, it was made to order by Dan Bartmann, and fortunately its specific grade is some 1-2 thousand gauss stronger than a normal magnet of its size. Although somewhat frail compared to other neodymium magnets, its increased gauss (13,700, or R45) contributes very significantly in its levitation stability over similar but lesser magnetic neodymium magnets.  The web site to view or order this magnet is below.

000529-013a
This is a view of the main levitated magnet.  Attached to both ends are lightweight plastic tubes.  On the left is the
Radio Shack "pill" magnet which is actually centered over the Hall.  The right hand spacer is used to contain a
counterweight to maintain a level balance.  The actual instrument just used solder wire stuffed in the end and
glued in place after the balance is achieved.
 

000529-021a
The above view simply shows the levitated magnet assembly atop the copper and graphite containment assembly.
Note the magnet is shorter in length than the graphite; this simply allows room for the levitated magnet to move a
distance with any seismic signals, and it also provides more diamagnetic support in case the movement goes the
distance either way.  The gold colored aluminum bracks (4), are simply arranged to act as a guide for movement
adjustments.  The inside of the guide was not epoxied down of course, to allow free movement.

 SEE: FORCEFIELD/WONDERMAGNET.COM

The graphite used here is simply to contain the levitated magnet within its assigned channel of horizontal directional preference.  However, it also is cut to a specific height, which has been demonstrated to be ideal for this specific levitated magnet and that magnetic gap force from the overhead ferrite magnets on the discs used.  Normally a number of brass adjustment screws and plates configuration could also be used to expand or close the gaps.    Overall, it has it multiple purposes, and is very important, although its not a rare item to adapt for use.  This sawed up diamagnetic graphite is from McMaster-Carr, 1/4" by 6"X6" plate  which appears to be slightly better than pure bismuth, and can only roughly be assigned a estimated value of ~ -190.   This guessed value is based on text book references of bismuth (presumed pure), of ~ -170.  The rectangular wedges are 1/4" thick by .450" length by .345" height; which yields a gap/s of .0475" (+ - .001") on each side of the top and bottom main discs.  In real escence, about any diamagnetic material from any source could be utilized here, where its known to be effective.    Probably the best material for the wedges would have been graphite of the same diamagnetic strength as the upper and lower layers disks; this would have helped limited any sideways or non-channel movement more.

  ON TO SOME QUAKE RECORDS WITH THE DIAMAGNETIC SEISMOMETER

 
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