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Subject: mettalic object detection

Date: 01/19/01 at 8:09 AM
Posted by: Jerry Holzer
E-mail: holtek@gate.net
Message Posted:

I'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 6" 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?

Jerry Holzer
Boynton Beach, FL

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