How to detect (open to friendly speculations) minute magnetic field changes ?
In application such as; * Detecting a crashed small aircraft in a very dense forest from another small aircraft fliying at a hight of 1000-4000 feet AGL. * Detecting metal pipe 10-20m below in ground. * Detecting a small metal boat sinked to depth of 00-200m from the surface of the sea. * Detecting earth magnetic field variations from a low orbit atellite or from a high altitude flying baloon.
Scientific american diy magnetometer project:
follow-up:
It won't be sensitive enough for your applications (or portable), somewhere to start though.
Do a search on "Proton magnetometer" for some ideas. There was an article in a very old Scientific American ( ~1960 ) which gave some details. Much more sensitive than the later force balance articles already cited. None are very easy to implement.
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