cComega virtual coil

[Aziz]

Next: Magnetic field vectors: Strength and Direction.

[Aziz]

Some commnents on standard omega coil:

Indeed, the absolute total effective magnetic strength integrated over the flux area of the RX coil tend to numerical instability (convergence instability) during balancing calculation. I had to increase the number of segments (wire elements) and minimizing the delta to overcome this effect. I will compare the standard concentric vs. standard omega coil in practice next week. I newer built a standard omega coil yet and I am looking forward to the results.
Aziz

[WM6]

Next: Magnetic field vectors: Strength and Direction.

Very interesting Aziz. Can you make some modification in position and shape of inner coils?? More like this shape:




In my testing the best for coin detection. L = approximately starting point position / proportion before tunning , but without much difference after nulling.
Thank you.

[Fred]

another shape idea.
Nulling could be performed by slightly offsetting the RX coil (?).
regards,
Fred.

[Aziz]

Hello WM6,

Very interesting Aziz. Can you make some modification in position and shape of inner coils?? More like this shape:




In my testing the best for coin detection. L = approximately starting point position / proportion before tunning , but without much difference after nulling.
Thank you.

I made the inner TX coil (TX2) a little bit bigger and opened the gap at omega position a bit (TX1). The RX, TX1 coil is the same, RX coil is ~ 1 mm above the TX2 coil. I think, the 1 mm distance gap is not enough for real world due to many windings ot the RX coil. Anyway, if the distance is changed, the balance position will differ along the X-axis.
An interesting question to proof is, the omega gap on TX1 coil. Should this be small as possible or not? I will proof this.

[Aziz]

The omega gap is now wider. No really big changes. Another interesting question is the radius of TX2.

[Aziz]

Hi Fred,

another shape idea.
Nulling could be performed by slightly offsetting the RX coil (?).
regards,
Fred.

Balancing is possible. But the magnetic field density shows an unreasonable result. There is a magnetic strength hole above and below the center of the coils. To get balanced the RX coil in the center of the coils, the N-TX1=40, N-TX2=33. It depends on the geometry of the RX coil (radius, position, height, etc.).
See the magnetic field strength cross section for your proposal below:

[Fred]

Hi Aziz,
Thanks for the reply.
Strange results!
I thought that by centerig the coils we could achieve a better (uniformely) shaped lobes.
Aparently for good results the fields should be reversed....
Regards,
Fred.

[Aziz]

Hi Fred,

Hi Aziz,
Thanks for the reply.
Strange results!
I thought that by centerig the coils we could achieve a better (uniformely) shaped lobes.
Aparently for good results the fields should be reversed....
Regards,
Fred.

You're welcome.
Canceling the magnetic field by an another TX coil is not efficient (signal-to-noise-ratio reduction). There is also another configuration possible: one TX coil and two RX coils.
The RX coils are operated on differential mode (in serial with different polarities). The geometry of the RX coils has to differ to detect any magnetic field changes. I have not investigated such configurations in practice yet.

[WM6]

The omega gap is now wider. No really big changes. Another interesting question is the radius of TX2.

Aziz, probably center of RX coil for best (coin) results have to be as close as possible under peak of EM field, although in account of RX coil diameter.
What do you mean?

[Aziz]

Hi WM6,

Aziz, probably center of RX coil for best (coin) results have to be as close as possible under peak of EM field, although in account of RX coil diameter.
What do you mean?

I have no idea. I have not really understand you - please explain me in detail, what you mean.

The RX coil positions shown here are allready on nulled (balanced) positions. Any offset of the RX coil would destroy the nulling/balance of the coil.

I suppose, the omega gap can almost be "zero" and there is no need for more space between the sharp bends of the TX1. For the purpose of more mechanical stability, the sharp bends could be even fixed together.

Anyway, practical experiments should help us, to interpret the EM field response. Then, we can optimize the coil to meet the desired specification.

By the way, I am just close by finding a "novel" coil design. A combination of the effects of concentric and mono coil effects. If my speculation comes true, then we can expect more sensitivity depth. But I have to build some prototypes and test the coils on the coming days. The proofed simulations shows: easy to build and tune. I am sorry, that I can not say more of this coil at the moment.
;-)
Aziz

[Mrand]

We are wondering above the optimisation of the coils. We are rehearing the one case when the head is working in the air. In reality the coil is working in the ground. The optimisation should take this situation into consideration. Is able the situation, that the coil theoretically better at air, is working poor at the ground. Example: symmetrical probe (with consideration of the ground) of type "OO" (Nexus) or typical "DD" towards unsymmetrical "omega coil". Maybe I am mistaken but I want to take note.
The Turkish KaraSav company producing military detectors, published text and the figure on its web page. I am asking Aziz for the analysis and the comment.

"OMEGA SEARCH COIL
This is one of the parts that have the most functionality about finding the metals due to the interaction of the detector with the ground.
In civil sector, our company achieved the goal of detecting the metals both small and deep under ground by using the search heads called D Coils in the detectors manufactured up to date since founded.
The search heads made of D Coil system have givven the best results in the civil sector and lots of foreign companies that followed our successfull works in the sector now produce search heads with D Coil system.
However, D Coil system has some disatvantegous ways related to the different search logics.
For example:
The sensing sensitivity of the search heads produced with D Coil system can change while detecting a glass nail positioned vertically or horizontally under ground . What I meant by the change in the detecting sensitivy was that the detection sensitivity is higher when the metal under consideration is positioned vertically and lower when positioned horizontally. This situation that can be neglected in the civil sector could result with big problems that can’t be neglected in military searches.
On January 2006, this problem should have been immediately solved when we are requested to study on a detector for military search and detection purposes.
Our R&D department who started workin on this goal designed the Omega Coil in a short time that we use in our AVCI XM-1 Detector.
By this search head that we called Omega Coil, the positioning of the metals under ground is not important anymore and it is provided that searches can be made without a change in the detecting sensitivity regardles of the positioning.
The Omega Coil system that we developed is patented and we are living the pride of achieving another very serious improvement in the sector.
The Features of OMEGA Search Heads
While making very sensitive and deep detections, it provides maximum sensitivity fort he small metals on the ground.
It has the capability of maksimum detection not only on one point but on the whole surface of the seach head.
The positions or the directions of the metals under ground do not have any effect in detection sensitivity.
It is not affected by the negative air conditions like hot, cold or moist by the special termoset composit material used in its design.
Detection of Metals, Ametals and Cavities is sharp and consistent.
The detection sensitivity is maximum while detecting the cavities, cable ways, plastic mines that consist of no metal or small metals or explosives with no metals in them."

Mrand

[WM6]

"...... On January 2006, this problem should have been immediately solved when we are requested to study on a detector for military search and detection purposes.
Our R&D department who started workin on this goal designed the Omega Coil in a short time that we use in our AVCI XM-1 Detector.
By this search head that we called Omega Coil, .....
The Omega Coil system that we developed is patented ...."

Mrand

Thank you Mrand. Very interesting. I can agree by most statement you posted here. Thanks.

But i am very surprised that one can give patent on Omega coil in year 2006???? Design of Omega coil (no matter of here factory name and adaptations) are known and already patented for decades, more than 20 years in this shape design:



So I cannot see nothing new in principle of coil working and designing in those year 2006 patented Omega coil, you informed us about by citation and posted picture. Really interesting, thank you.

[Mrand]

Link of KaraSav firm www site:
http://www.karasav.com/ing/avci/index.asp

Mrand

[WM6]

...
The RX coil positions shown here are allready on nulled (balanced) positions. Any offset of the RX coil would destroy the nulling/balance of the coil.

I suppose, the omega gap can almost be "zero" and there is no need for more space between the sharp bends of the TX1. For the purpose of more mechanical stability, the sharp bends could be even fixed together.
Aziz

Hi
agree Aziz, coil have to stay nulled and I am not contra tunned coils. Tray only to find such omega construction that center of RX coil in nulled position is placed asap closer to vertical axis of peek of max field strength (graphically noted by your application).

I perform some homelab test (no field test at all) and find that my latter suggested shape (also posted in my answer to Mrad) suit at my best that I can do to reach this goal. But in this case RX become someway small to still keep good discrimination, at the same time it is very sensitive to small things like (ear)rings.
Regarding gap, maybe to sharp bend of TX coil on gap are some self destructive and have to be more rounded, like in my suggested design. If you can do some modification on this?