cComega virtual coil

[WM6]

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

Mrand

Good final coil design, Mrand, thanks, hope not to heavy:

[Aziz]

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

Hi Mrand,

Why I am showing the H = magnetic field strength is, there is no permeability incorporated in it. The induced voltage on Targets is dependend on B = µ0*µr*H. µr is the relative permeability and is 1.0 for air. The nulling/balancing stay remain, if the coil or of underneath is "filled" with same material (constant µr).

The shown omega coil from the turkey company is a real good design. It is same of type allready shown here, except the coils have elliptical shape. This design can be further optimized to achieve more depth propably.
But I am in doubt about the patented design. Omega coils are very old and very known coil designs for more than 30 years. If anybody has the patent, it would be interesting, what they have really patented.

In general, omega coils are neglected in the last years from the industry. I am wondering why.

Aziz

[WM6]

How deep with military Omega coil MD?

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

Mrand

Very clearness.
How deep with military Omega coil MD:




http://farm3.static.flickr.com/2277/...2b2fda.jpg?v=0
http://farm4.static.flickr.com/3141/...36784a.jpg?v=0

[WM6]

Hi Mrand,
The shown omega coil from the turkey company is a real good design. It is same of type already shown here, except the coils have elliptical shape. This design can be further optimized to achieve more depth probably.
Aziz

At first sight I am thinking on elliptical form too, but seems it was only more effective view or projection ground. On other picture from their site it was round design, as you can see on some previous posted picture. Circular and shaped as original Omega coil.

[Aziz]

Hi WM6,

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).

This is impossible - not in our universe!

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?

There is no need for rounding the sharp bends. You will uniform small local magnetic fields, that end to complex detection area and would cause phase shift anomalies and therefore discrimination anomalies. If you want do rounded ends, then do it. This design opportunity has only small effects on the whole coil.
Your requested modification cause me lots of work. Re-designing the computer model, etc.. But the result would not change much.
Aziz

[Aziz]

At first sight I am thinking on elliptical form too, but seems it was only more effective view or projection ground. On other picture from their site it was round design, as you can see on some previous posted picture. Circular and shaped as original Omega coil.

For some purposes, an elliptical shape would be convenient. Such as on the complex terrains, an elliptical shape is more practical. May be I should show all you, that there is really no difference.

[Carl-NC]

In general, omega coils are neglected in the last years from the industry. I am wondering why.

Probably they don't perform well in mineralized soil, because compression of the transmit field unbalances the coil. For mineralization, the best coil to have is one that is purely symmetrical... concentric is good, DD is better, OO is even better.

- Carl

P.S.-- The earliest reference I know of to the omega coil is a 1969 patent.

[Aziz]

I enclose the analysis of the mentioned elliptical omega coil from turkey. The RX coil is set 4 mm above the TX coils (realistic condition). It is almost on the center position (4 mm offset to x-axis) of the coil arrangement (caused from the z-offset). The coil arrangement is "exact" in contrast to other manufacturer.
See the pictures below:

[WM6]

Probably they don't perform well in mineralized soil, because compression of the transmit field unbalances the coil. For mineralization, the best coil to have is one that is purely symmetrical... concentric is good, DD is better, OO is even better.

I was thinking that it was neglected because of difficulties in serial factory manufacturing. I find your opinion, Carl, about symmetrical vs unsymmetrical in mineralized soil very interesting. I form a picture about this, that coils which are easy (or not so delicate) tunable, are more stable in all sorts of soils and opposite no matter of shape. Relation between coil symmetry and kind of soil regarding coil stability are something new to me and i will perform some test in such way in future. Thanks for your statement.

[Aziz]

Top view to the coils (z=4 mm, on the RX coil plane):

[Aziz]

Probably they don't perform well in mineralized soil, because compression of the transmit field unbalances the coil. For mineralization, the best coil to have is one that is purely symmetrical... concentric is good, DD is better, OO is even better.

- Carl

P.S.-- The earliest reference I know of to the omega coil is a 1969 patent.

Hi Carl,

this is an interesting thesis, which has to be proofen. But I am not really convinced. Prototypes should give the answer.
Aziz

[WM6]

I enclose the analysis of the mentioned elliptical omega coil from turkey. The RX coil is set 4 mm above the TX coils (realistic condition). It is almost on the center position (4 mm offset to x-axis) of the coil arrangement (caused from the z-offset). The coil arrangement is "exact" in contrast to other manufacturer.

I imagine myself, that primary goal by Omega coil is to reach as small as possible inductive influence between TX and RX coil. To reach this we can manipulate with geometry (position and dimension) of TX inner loop and RX coil. I tested this with 4 variable parameters: TX-out diameter, TX-inn diameter, TX-inn position and RX position (fixed RX diameter). It is easy to build such variable testing Omega coil and play with. RX was made first on given L , shielded and tape isolated , then we coil up TX follow specific L at appr. diameter 4 x RX. After shielding and isolating, only TX coil are shaped in desired form of Omega and RX only different positioned. I shaped similar with Turkish coil too, but reach best results on shape last posted, for small items sensitivity (RX positioned very deep in TX-out coil and from this spot my suggestion.

[Aziz]

I imagine myself, that primary goal by Omega coil is to reach as small as possible inductive influence between TX and RX coil. To reach this we can manipulate with geometry (position and dimension) of TX inner loop and RX coil. I tested this with 4 variable parameters: TX-out diameter, TX-inn diameter, TX-inn position and RX position (fixed RX diameter). It is easy to build such variable testing Omega coil and play with. RX was made first on given L , shielded and tape isolated , then we coil up TX follow specific L at appr. diameter 4 x RX. After shielding and isolating, only TX coil are shaped in desired form of Omega and RX only different positioned. I shaped similar with Turkish coil too, but reach best results on shape last posted, for small items sensitivity (RX positioned very deep in TX-out coil and from this spot my suggestion.

I have to implement some efficient and coupling factors on coils and we can see in the future, which coil has more "power". At the moment, it is not possible to read/see this.

[Fred]

Could it be possible to reflect (deflect) all the "upward" field so it is only transmitted downside,in a similar principle of yagis antennas ? But as the dielcetric properties of the reflector would most probably be a problem , maybe an active device like in phased arrays?

After all, 50% of energy is lost in all those coils...

just a thought,
regards,
Fred.

[Aziz]

Hi Fred,

Could it be possible to reflect (deflect) all the "upward" field so it is only transmitted downside,in a similar principle of yagis antennas ? But as the dielcetric properties of the reflector would most probably be a problem , maybe an active device like in phased arrays?

After all, 50% of energy is lost in all those coils...

just a thought,
regards,
Fred.

I am sorry, this is not possible.

Heureka! Now I have found a very well magnetic field profile for a difficult to build (tune/balance) coil system. This could be a reasonable coil for pin-pointing. Its maximum is on center.