Stainless Steel Detection

		Quote:			Posted by Oseania
	I read that most PI metal detectors don't detect some stainless steel grades. This is because the conductivity of the material is so low that the eddy currents dissipate before by the time pulse delay has ended and the sampling begins. Is it possible to detect stainless steel with VLF metal detectors and has anyone tried it?

pi can detect stainless steels but it loses its deepness to detect.

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		Quote:			Posted by Oseania
	Hi, In my application the stainless steel is under conducting mineral rocks. So eddy currents coming from the mineral rocks might mask the weak eddy currents in the stainless. I think that VLF with discrimination might work however I haven't any practical experience from it.

PI has no effect in mineral rocks even on salt water or highly miniralized soil. discrimination is useless in pi.

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This is a good question and a tough one to answer. Some grades of stainless steel are magnetic and some are not. It depends on the alloy. Those that are magnetic are detected like any other ferrous metal while those that are not react like gold or silver. Conductivity has little to do with the detection. The ability to develop a magnetic field does. Some ceramics are magnetic and are not metal. They can be detected using a metal detector. Before you all go leaping out to try this, remember that most ceramics are not magnetic.

A PI detector isn't going to ignore the steel because of it's conductivity but because it cannot develop an eddy current inside the metal. Instead, it develops an eddy current field on the surface of the metal like gold and silver. The surface eddy current is not as strong as the internal one developed by ferrous metals so an inverse signal strength happens in your target. The strength is not what gives you a target response. The field collapse time is what does that in a PI detector. The decay of the return pulse is critical to detecting a signal so you might be able to find it with a detector that has an adjustable pulse width.

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