Dual Field Pi Coils

[detectormods]

The 1(Width) :1.68 (Height) is not performing better. It can be approximated with the 1:1 and 1:2 ones either elliptical or rectangular.

Doing an accurate analysis is quite time consuming process and causes a lot of work. So I want to limit the work to the well known form factor coils.

Aziz

Hi Aziz,

In the real World the Golden ratio coils make for a bladed pattern, on constructing various coil shapes there are pro's and con's for every shape.

I found that deviation from a mathematical representation of Phi caused a conical pattern while an adherence to Phi made for a blade pattern.

It interesting to do real experiments in the field.

[Aziz]

Outperforming the Dual Field Coils

Hi all,

I will show you, which coils are performing better.

I proposed a Tripple Field coil and Spiral coil former. All together in a comparison shows, how they perform.

TF 0.33 0.66 1.0 means (Tripple Field Coil):
Coil1 at 0.33*R, Coil2 at 0.66*R and Coil3 at 1*R, where R=outer radius of coil.

TF 0.5 0.75 1.0:
Coil1 at 0.5*R, Coil2 at 0.75*R, Coil3 at 1*R

The Tripple Field split coils have all the same number of windings.


Spiral 0.33-1 (Spiral Coil):
Spirally wound coil starting at 0.33*R and ending at 1*R. The number of windings are evenly distributed from starting radius to ending radius.

and so on...

Fortunatelly, spiral coils can not be patented anymore. It is in the public domain. Anything new to the prior art is also public domain now. I made this analysis on the GPOZ forum already, dated at 19.Febr.2009! You can see this there if you like.

Cheers,
Aziz

PS: the last picture is a log-scale (not linear as shown).

[detectormods]

Hi Aziz,

I do not think there is a lot to be patented these days due to all the new idea's being discussed on the net.

Sometimes it is worth quickly lodging a patent to protect an idea before a large corporation locks it up.

A large company can claim prior art by saying they were working on the very thing that gets put into the public domain.

Keep up the good work with coil simulation, now be a Capitalist and sell it as a design program to the experimenters..

I am off to the Gold fields to do some tests on 4 new designs, it will be interesting to document the results.

[Aziz]

Hi detectormods,

Hi Aziz,

I do not think there is a lot to be patented these days due to all the new idea's being discussed on the net.

Sometimes it is worth quickly lodging a patent to protect an idea before a large corporation locks it up.

A large company can claim prior art by saying they were working on the very thing that gets put into the public domain.

Keep up the good work with coil simulation, now be a Capitalist and sell it as a design program to the experimenters..

I am off to the Gold fields to do some tests on 4 new designs, it will be interesting to document the results.

I am not interested in making money - it has no meaning to me except of buying some parts to make more findings possible.
I have not the big bucks to lodge a patent. I want to share my findings with all of you. Coil software won't be given away.

But I would like to know, how the proposals behave in the field. I hope, you are willing to share your experiences. Some feedback would help to optimize the coils further.

I would suggest to try the spiral coil 0.66-1 or the 0.75-1. The first few detection cm's can't be used either. To make the design easier, it could still be a rectangular spiral coil.


Aziz

[Aziz]

BTW,

I forgot the give an unit to the x-axis on the graphs.
The target distance is given in cm on the x-axis.

Who remembers Gary's spiral coils? There is an overrun to his coils obviously.

PI coil wires should be a Litz wire. They can be very thick. Instead of making a thick coil, it is more advantageous to make a spiral coil instead. Higher coil bundle width instead of coil bundle height.


Aziz

[Stefan]

Hi Aziz,

There is a compromise as when you make the height of the coil much less than the width of the coil the shield capacitance will increase. This is of course more profound on smaller coils and elliptical coils. So it is all a question of compromise to obtain optimum results by reducing the inter winding capacitance and the shield capacitance.

Regards,

Stefan

[Aziz]

Hi Stefan,

Hi Aziz,

There is a compromise as when you make the height of the coil much less than the width of the coil the shield capacitance will increase. This is of course more profound on smaller coils and elliptical coils. So it is all a question of compromise to obtain optimum results by reducing the inter winding capacitance and the shield capacitance.

Regards,

Stefan

yes, that's true. One must consider the coil perimeter too. The coil flux area should be maximized and the perimeter should be minimized at the same time. This is a good exercise for someone, who likes math.

But there are applications, on which the parasitic capacitances don't matter. Then a IB spiral coils (TX and RX spiral coil) would have the most sensitive performance then.

Aziz

[Aziz]

Further Dual Field Coil Analysis

Hi all,

I want to show you, how the Dual Field coil behaves to different size targets. And how the Dual Field coil compares to other coil types (see below).
T=10: 10 mm target diameter
T=20: 20 mm target diameter
T=40: 40 mm target diameter

Aziz

[Aziz]

Dual Field Coil Turn Variations

This is the Dual Field 0.5 coil, where the turn ratio of the inner to outer windings are varied (see below).

Syntax:
N=inner:outer windings turn ratio

N=1:3 means, the outer coil winding turns has 3 times more windings than the inner coil
N=3:1 means, the inner coil winding turns has 3 times more windings than the outer coil

All variations have the same inductance L and same coil flux area of 500 cm² (outer coil).

Aziz

[Rov]

Hi Aziz,in your graph softwares what do the graduations for X-Y (horizontal to vertical) mean too people that dont know an want to interpret simply?you do not have reference to scales for people to follow.Thanks!

[Aziz]

Hi Rov,

Hi Aziz,in your graph softwares what do the graduations for X-Y (horizontal to vertical) mean too people that dont know an want to interpret simply?you do not have reference to scales for people to follow.Thanks!

x-axis: target distance in cm from the center position of the coil arrangement
y-axis: induced voltage from the secondary magnetic fields (target's eddy current caused magnetic field)

The absolute value of the induced voltage is not important. Only the relation to the other coils or configurations. As all the configurations are normalized to a particular specification, one can compare different coil configurations together. It's just tells, how an equivalent coil configuration compares to other equivalent configurations.

If I do not normalize, then it would be difficult to say, whether a configuration performs better or not.

All coil configurations are normalized to L=300µH (total coil inductivity) and 500 cm² coil flux area (coil coverage area). This means, all configurations will emit same magnetic field energy to the target.


Aziz

[detectormods]

Hi Aziz,

Back from Gold field tests.

Real tests in the field show that the noise does NOT INCREASE with a split winding. This is different to my bench testing on a bed of hot rocks, if anything the dual field coil was quieter than one with a diameter of the largest winding.

[Aziz]

Hi detectormods,

Hi Aziz,

Back from Gold field tests.

Real tests in the field show that the noise does NOT INCREASE with a split winding. This is different to my bench testing on a bed of hot rocks, if anything the dual field coil was quieter than one with a diameter of the largest winding.

thanks for your valuable feedback and field tests. This is indeed a good news. One could make a 0.67R and 1R split coil for more hotter grounds. This should even be more quiet. Then quite big coils (18"+) could be used in the field with the benefit of sensitivity to small targets too. The high sensitivity in the near detection zone can not be fully used due to some distance of the coil to the ground.

Aziz

[IBGold]

Hi Aziz,
Here is a picture of my 28 x18/15 x 10 Duel-Field and I concur with Peter on the performance.
Regards,Ian.
http://i806.photobucket.com/albums/y...lFieldCoil.jpg

[Aziz]

Hi Ian,

Hi Aziz,
Here is a picture of my 28 x18/15 x 10 Duel-Field and I concur with Peter on the performance.
Regards,Ian.
http://i806.photobucket.com/albums/y...lFieldCoil.jpg

it's looking very very nice. It's a marvellous craftsmanship.
Aziz