General Questions

Gentlemen,
   Please be patient and forebearing with this newbie, but I have some rather elementary questions concerning magnetometers.  First, when used to detect large metal objects in water is the detection range greatly reduced?  It seems intuitive that it would be just due to the fact that water is ~800x denser than air.  My second question is concerning the general use of said magnetometer.  Just a kind of general primer to get started.  Am quite interested in building one and any recommendations on the type and any user friendly schematics would be appreciated.
Warmest Regards From San Antonio,
Jimbo

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Christian is right about both of his points but there is evidence that a long time in salt water can create enough embedded salts (not the kind that tastes salty) in wood to allow a magnetometer to sense the hull of a large wooden vessel by sensing a very weak anomaly. A skilled magnetometer operator can spot that kind of anomaly.

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		Quote:			Posted by redflex900
	I would like to know if the magnetometer can detect the  bigger iron chest if there several ferrous trash around such as cans,rusting bolts, etc? Thanks.

Sorry, no. It looks like a bigger iron target. But it does depend on the distance between the smaller and larger objects. Lots of distance can make it easy to pick out the large anomaly but if they are densely packed near the object, you won't have any luck picking out the chest.

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To be sure, run your detector over the area and see what size the trash seems to be. Nails and such are sometimes too small to create an anomaly but 200 of them dropped in a small pile probably will. Your chest will have to be mostly magnetic, too. That's something to consider. If your buried object is a thin steel box with non-magnetic material inside, you might not see it at all with a magnetometer. If it is deeper than 20 or so inches, forget using a PI. You may need a two box unit. A two box unit will ignore the trash and detect a large METAL object, magnetic or not, down to around 3 meters if it has a lot of mass.

How about you stop being coy and simply describe your potential target without revealing the location? There are some very knowledgeable people here who can help you but this kind of discussion is rather pointless. Tell us how deep you think it is. Tell us what you believe the chest is made from. Tell us what you believe is inside. Give us an idea of the terrain. You will get better answers that way.

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With that much cement around the item, it seems as if whoever buried it was never planning to come back to it.

The two box unit seems like your best option on this one. I once buried a Band-Aid box full of Mercury dimes when I was a kid. More than 30 years later, I went back and dug it up. The box was rusted through and through and I had to sift the soil to get the dimes. Had the box disintegrated entirely, I still would have found it because a metal detector can detect silver (and gold) quite nicely. If your box has disintegrated, you might not be able to locate it with a magnetometer. At the depth you are working, you could use probe rods after you scrape off the top 3 feet or so.

A GPR might just be able to "see" it but that depth of 3 meters is at the end of the range for a GPR. If you're dead sure it's there, rent a backhoe and go for it. I'd love to hear of your result. Good luck!

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