sci.physics.electromag

On Apr 9, 5:52 am, oeg...@gmx.de wrote:
> I am publishing a new concentric co-planar coil with strong magnetic
> field for metal detectors.
> Former concentric co-planar coils consist of relative small receive
> (RX) and bucking (canceling) coil. So the magnetic field density over
> the flux area of the RX coil was highly cancelled by the bucking coil.
> This new design enables lower canceling the magnetic field density on
> the center position of the coil arrangement. Also the relative big RX
> coil covers much more detection area. The hot spot of the coil (max.
> sensitivity position) is on the center position of the coil
> arrangement. The main transmit coil (TX) is on the center position of
> the coil. The bucking (canceling) coil is outside or on the same core
> of the RX coil. The main magnetic field is provided by the TX coil.

I think no matter what you do, the laws of physics prevent you from
getting a greater sensing distance. Metal detectors only see objects
at distances of a few times the width of the head.

The only difference between the transmit and recieve coils is that the
cross section of the receive coil determines how much noise the
receive circuit is fed. You can freely exchange the two and you
will get the same signal from a given target.

Placing the two coils on the same plane but offsetting their center
points so that the coupling is zero is another way to go. It makes
the head bigger than the designs with bucking coils but the detection
range is better by about the same amount.

The nulling issues only apply to "frequency domain" metal detectors.
"Time domain" detectors have different issues.

Are you building a multifrequency circuit? If not, you can cancel in
the electronics or use the very old oscillator frequency shift method.
>
> See magnetic field cross section and the coil arrangement on the
> following link:http://www.thunting.com/geotech/forums/showthread.php?t=3D1=
4121
>
> By issue date and time and the publishing this type of concentric co-
> planar coil, it isn't anymore possible to patent my invention. So it
> isn't novel anymore now. Take this coil for de-mining. It is a gift
> for mankind.
>
> Rosenheim, 9. April 2008,
> Aziz =D6g=FCt