Metal Detector Schematic Question

[quantumtangles]

I would like to build a metal detector capable of discriminating between ferrous and non-ferrous metal.

Commercial manufacturers seem to have been careful not to disclose their schematics in the literature.

Google and YouTube reveal interesting schematics and projects but only for basic metal detectors.

But does anyone know where I might find schematics for higher end discriminating metal detectors (preferably without an LCD display or 3D imaging technology)?

In other words, can you suggest a schematic for a discriminating mid-level metal detector that would make for a good project

Your suggestions would be much appreciated.

 

[quantumtangles]

Candidate Schematic

Just found a Russian schematic that may be promising. Any comments would be much appreciated.

Here is the link for the Russian Schematic, itself a link from a Polish engineer's project.

http://tomek.ucoz.ru/_pu/0/32059.png

I hesitate in the hope of building a device capable of detecting non-ferrous metals at depths of 20cm or more.