GROUND EFFECT

The ground itself can be conductive and react like a target, giving false signals. This is called ground effect and it is a particular problem in mining areas where metallic ores may be present and also on the beach where water and salt may combine to make a highly conductive detecting surface. Motion machines with automatic ground adjustment will struggle in these situations because the detector cannot know that it is in a difficult operating area and so it will constantly detect the gound as if it were a target. Reducing the sensitivity will alleviate the problem, but of course detection depth will be reduced. Non-motion machines can be manually adjusted to the ground conditions and will operate well in most situations. However, rapid movement from, say, wet ground to dry ground may require the ground setting to be changed. Ground adjustment controls are a bit like discrimination setting. In effect, the user is showing the detector a piece of ground, and telling the detector to ignore it.

It's all clever stuff, but it's just the laws of physics that we're up against here. In air it is possible to put an enormous amount of energy into the search-head, and detect metal objects from metres away, but as soon as you lower that search-head to the ground, the machine starts blaring away because it is actually detecting the ground. So you can't use too much power in a metal detector. Sorry. That's the way it is. We're up against the laws of physics.