[rescue] Oh no! This poor Origin server.....
mcguire at neurotica.com
Thu Apr 1 22:24:31 CST 2004
On Apr 1, 2004, at 11:16 PM, Phil Stracchino wrote:
>> So...use it as a hypersensitive metal detector. Not to find watches
>> on the beach, but to find coins under a thousand feet of water.
> Wow. That sensitive?
> How do you turn the output signal into location
> information? (Or is this left as an exercise for the student?)
Well, the frequency of the signal you get out of the kerosene cell
can be, with a tiny bit of math, turned directly into an absolute
measurement of the intensity of the local magnetic field. Now build
two identical units, stack one sensor atop the other, maybe 3-6 feet
apart, mounted to a pole of some sort. Suspend it so it always stands
as close to vertical as you can manage.
Now measure the *difference* between the two frequencies from the two
sensors...Voila, a proton precession gradiometer...measuring the local
Now...Put this on a boat, and do a cartesian sweep pattern...plotting
the gradient with false color or something like that on an X-Y grid.
You will see a "bump" if you pass over something metallic, and with a
little bit of math, you can calculate (at least I *think* you can
calculate) the absolute distance between you and the object.
>> Or use it to detect cars & trucks driving by, just for shits &
> Unfortunately, I'd probably create a bigger signal just walking around
> the room, with all the metal in my leg.
> Then again, it *is* stainless steel, which is diamagnetic ....
Dave McGuire "PC users only know two 'solutions'...
Cape Coral, FL reboot and upgrade." -Jonathan Patschke
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