[rescue] Oh no! This poor Origin server.....

Dave McGuire mcguire at neurotica.com
Thu Apr 1 21:53:44 CST 2004

On Apr 1, 2004, at 10:48 PM, Phil Stracchino wrote:
>>   Go to Home Depot (or equiv.) and get a 9-12" section of 3 or 4"
>> diameter PVC pipe and some end caps.  Fasten one end, fill it with
>> kerosene, then fasten the other end.  Be sure to get a good seal.  
>> Wrap
>> a few dozen turns of fairly thick (~14ga) wire around it.
>>   Build an amplifier and a bandpass filter centered around 2.46KHz.
>> Get a large-ish 12V battery (like a lantern battery) and a beefy DPDT
>> toggle switch.  Wire up the bandpass filter/amp combo, the coil around
>> the kerosene cell, and the battery in such a way that the coil can be
>> alternately switched between the battery and the filter/amp combo.
>> Connect the output of the amp to a speaker or a set of headphones, as
>> well as a frequency counter.
>>   Voila.  A proton-precession magnetometer.
> Hmm.  I believe I understand how that would work.  Cool.

   Yup.  It's a truly ingenious idea.

>>   Of course, myself, I would do it with some big MOSFETs, a
>> microcontroller (no, not some monster with an MMU and an operating
>> system, Josh. ;)), and an LCD.
> And a solid-state relay instead of the DPDT switch?  (Faster switching
> time)

   Nope...that's what the MOSFETs are for.  Sub-1-ohm "on" resistance, 
baby! 8-)

> (Of course, I still have no idea what I'd use one for.  I mean, I know
> what it DOES, I just don't know what I'd DO with one.....)

   Well...think of it in the context of the geomagnetic field.  Any 
ferrous metals within a magnetic field will distort that field...which, 
when viewed from the perspective of a single point in space, will be 
apparent as variations in the intensity of the field.

   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.

   Or use it to detect cars & trucks driving by, just for shits & 


Dave McGuire          "PC users only know two 'solutions'...
Cape Coral, FL          reboot and upgrade."    -Jonathan Patschke

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