Howdy PSN Folks,

Ill try to describe this using words,
If my words make no sense, then tell
me, and Ill make a diagram.
The sensor itself is not expected to be 100% vertical in nature.
Possibly it is better suited for the Horizontal Plane.
Only intended for P/S/L Local or Regional events.

GIVEN:
1. Copper Pipe fitting about 1.5 Inches tall, (Home Depot,or?)
   Approx: 22.90mm ID
   Approx: 24.85mm OD
   this fitting has no crimps in the middle
   perfect as you might get cylinder
   This is the primary coil and Damper of the system.
2. AWG 30 enameled Cu wire about 200ft+ (radio shack,or?)
3. Electricians Tape, rubber (not plastic)
4. 10 or so circular 0.7 to 0.75 inches Diameter Neo rare Earth chrome plated magnets
    stacked in a cylindrical pile.
5. 4.5 to 5 Pounds Avd. Pb (LEAD) melted and poured into a regular empty Al soda can
    to give it shape. Eye Hook screwed solidly into the pre-drilled center top
   of formed lead chunk. (must use care here)
6. 2inch by 2inch 1/4 to 1/8 inch thick soft steel plate
    (can be cut from a flat bar you can find in a hardware store)
7. HW store Spring which will extend at least 11 inches when weight is added.
8. Tripod with adjustable vertical hook to hold spring.
9. 100% shielded three wire microphone cable.
10. Op amp (like OP177G ) with 1Meg  feedback and two 1000OHM to 100k input resistors.
      gain of 1000 to 10 only for preamp. (I used x1000)
      This is to be the Preamplifier. USE X10 for maximum Bandwidth. X1000 Ok for seismic stuff.

Do This;
BUILD COIL
  1. Wrap a thin layer (1 layer stretched) rubber tape
    around middle of copper fitting leaving a mm
    or so bare copper at either end.
  2. Wrap 30AWG Cu enameled wire wire
    full 200 feet or more (N=500+) around the
    Middle area previously covered with rubber electricians tape.
    I hand wound it indiscriminately. Tight Coils created exactly
    might produce more turns and better results.
    You will need a formal coil winder machine to do it right.
  3. Cover Coil with outer layer of rubber electricians with thin
    tight layer of one to two layers of tape as desired.
    This is the secondary voltage producing coil of the transformer.
    To be sent to the preamplifier.

BREADBOARD AMPLIFIER USING +/- 3 to 5 VDC Split Supply (I used Batteries D Cells)

HOT GLUE THE SOFT STEEL PLATE TO THE BOTTOM OF THE LEAD WEIGHT PREVIOUSLY POURED
FIRST YOU MUST PREHEAT THE SOFT STEEL PLATE TO 100F or a bit more for better adhesion to lead weight

PLACE THE COIL ON A PLATFORM (Ceramic Tile ?) UNDER THE TRIPOD, HOT GLUE BASE OF COPPER FITTING TO CERAMIC/GRANITE/MARBLE TILE

USING THE MICROPHONE WIRE, ATTACH ONE SIDE OF COIL TO + input of amplifier (maximum input resistance)
AT THE AMPLIFIER ATTACH THE SHIELD TO POWER GROUND ALONG WITH ONE SIGNAL WIRE
THE SHIELD IS CONNECTED TO NOTHING ON THE COIL SIDE
THE COIL IS CONNECTED TO TWO WIRES CONTAINED WITHIN THE SHIELD

ZERO the amplifier, with just the coil attached (NO MAGNETS NEAR THE COIL)

ATTACH the magnet pile, vertically, to the steel plate, at the bottom of the lead weight

HANG SPRING FROM THE TRIPOD

HANG THE LEAD (Pb) WEIGHT FROM THE SPRING

CENTER THE COIL UNDER THE MAGNET PILE

LOWER MASS, INSERTING THE MAGNET PILE INTO THE COPPER FITTING, POSSIBLY WITHIN
two mm of touching bottom. SO that it is free to move within the copper fitting.


WHAT TO CALL THIS:

I call this a transformer/Damper velocity sensor.
The mass will be damped (to what degree I'M uncertain)
As the magnet pile moves within the copper fitting.
A voltage is generated in an isolated fashion
within the secondary coil just wound.

NOW,
BUILD IT TEST IT, or if you know, tell me, if this will work
as any kind of seismic sensor/damper combined.
I have built it already and am waiting to connect it
as a second channel to the 16 bit A/D converter.

BTW:
The links in my personal web page were wrong, simply because I used( \) instead of (/)
but, it works in my browser no matter which way it is. It took a British pen pal to point this
out to me, why could none of you tell me this yourselves ? It is obvious you guys
do not use the same MS browser IE8 ?? I remember you told me there were errors
but since it worked for me, I was not sure this was so. Are people afraid to
say exactly what's wrong ??
A caution to me can mean nothing, if the problems are not pointed out, in an itemized fashion.

Just For Fun:
Get a copper pipe 2 Ft or so long
Take a magnet pile of various numbers of magnets
Drop them vertically through the copper pipe
determine the terminal velocity of the different magnet piles.
It is my guess the lower the velocity the greater the damping.
The smaller the gap the lower the velocity.
But you need an even  gap of like 1 to 2  mm all around for this sensor to work right.

Regards,
geoff
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