short range locator

[Tony]

Hi,

I'm looking to build a short range detector to locate small pieces of metal used as markers(around 2 x 10mm, prob. copper, but other metals considered) at a distance of at least 5cm, preferably up to 10cm. Can anyone advise on the most suitable type of design to use - induction balance or PI? Any suggestions regarding suitable circuits and coil designs?

Thanks.

[Gary]

Re: short range locator

Not sure if I understand you correctly, but my PI detector with a Very Small coil, 1/2 in diameter should work ok. sensitivity can be reduced by lowering the gain of IC9 on my schematic.
I assume you don't care about descrimination against some metals.

[Sean Goddard]

Re: short range locator

PI, IB?????

Too complicated by far.

Look at the CS209 by ON Semiconductors. With a few extra components it works out at about $5 to make a 1/2 decent metal/proximity detector.