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Subject: Re: mettalic object detection

Date: 04/09/01 at 3:36 PM
Posted by: mesut_gunes
E-mail: mesut_gunes@mailcity.com
Message Posted:

In Reply to: mettalic object detection posted by Jerry Holzer on 01/19/01 at 8:09 AM:

'm trying to decide what the best approach would be to sense a metallic object passing
through a two-foot diameter coil. The targets are relatively large (about 7" long) but are
made of stainless steel. I'm familiar with industrial metal sensors for conveyors, but I
don't need anything that sensitive. Those things will sense the hemoglobin in the blood
running through your hand (much to the dismay of unwary machine operators)!

So the question is do I pursue a beat-frequency oscillator or phase-shift detector circuit
like a terrestrial metal detector, or do I use an eddy-current or other field-loss circuit like
a prox? What throws me is the size of the coil...I'm just not familiar with the physics of
coils that large! It would be an advantage to only need one coil, so I'm kind of biased
towards a prox-type approach.
Any advice?

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