Hi.
Seen often prospectors sweep their metal detector coils a couple of inches above soil. Is it a habit, a convenience, protection from bumping or a need to do it that way ?
The sensitivity of some detectors drops considerably adding two inches under the search coil, specially on smaller or deeper targets. See no harm in dragging them on top of soil directly for better responses. Plastic cover to wear somewhat, but may be much more productive.
What is true about it ?
Been looking at pulse induction PI instruments; what is the performance/operation difference to non-PI units ? How do discriminating and not units circuits differ ?

 

I know very little about metal detectors. I do know this - distance from target doubled will drop the signal by a factor of four times. So the closer you can sweep the more detection reflection you will receive. As for the other types mentioned - I know nothing about them. That's all I got.

 

Field-Strength / Directionality / Gain
have everything to do with the specific design of the Detection-Coils.
A well designed Coil may have an extremely concentrated Detection-Pattern
which "looks" much deeper than an inferior design.

Being able to hold the Coil up off the ground enables much more area
to be scanned in a much shorter period of time.

The detection Circuitry does not need "time" to detect something,
it is virtually instantaneous,
so sweeping-speed can be extremely fast while not missing anything.
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