metal detector

I need to build/purchase a metal detector which can measure metal(soft iron,etc) buried underground up to 8cm. The sensitivity of the metal detector if possible,can be adjustable. The size of the metal detector is preferably around 4" x 4". If you have any related websites, please tell me.

 

[uWaveFDL]

http://www.detection.com/super/sale.html

the above site has links to most of the metal detector manufacturers. Check out the specs on each, there are a lot of options available.
I hope this is of some help.

 

On Semiconductor produces the CS209A IC which you could build a metal detector around.