Dual Field Pi Coils

[Aziz]

Hi detectormods,

Hi Rov,

I carried out some tests using a bed of nasty ironstone hot rocks with a 10" single wind mono of 280uh and again with a 10" and 6" split wound coil. The noise did increase but by only 1.5 db. This indicates that there is some extra proximity effect from the second winding to the ground matrix. This may have a slight adverse effect with very high gain and low noise designs as per the Minelab P.I detectors. In the real World it may not be an issue at all. More tests need to be carried out.

did the nasty ironstone hot rocks lie on the bed or in the bed (in the ground). If they did lie in the ground: evenly distributed on different depth or concentrated at some depth layer?

Aziz

[detectormods]

Hi Rov,

I carried out some tests using a bed of nasty ironstone hot rocks with a 10" single wind mono of 280uh and again with a 10" and 6" split wound coil. The noise did increase but by only 1.5 db. This indicates that there is some extra proximity effect from the second winding to the ground matrix. This may have a slight adverse effect with very high gain and low noise designs as per the Minelab P.I detectors. In the real World it may not be an issue at all. More tests need to be carried out.

[Rov]

Yes I agree,you dont get something for nothing!Ive noticed the diminished result for overall depth over say an 12inch pure mono wind.with the dual loops you can change the critical winds up or down between the two coils to change the parameter,for marginal increase of sensitivity or depth.depending on which of the windings you change.
eg .simply,up a couple of turns an reduce on turns in the other loop to still match an ideal,overall total coil resistance an inductance an total coil capacitance. so your PI detector will see it an drive it suitably.
I dont know what test bed of PI detectors you use for your results?
I only use my Pulsemate Pi detectors an unmodified standard Minelab Sd/GP Pi machines.with no smoothing or VCO/GPM style mods. I dont have use of a Whites TDI or similar.Pity?
Any conclusive results from my few DF builds on the GPX series are in WA. on active gold prospecting endevours.right now. an the users want to buy these coils.So something must be a + or positive towards their build.
Hope to hear of your coil testing results,detectormods.
think you may well find in the Df configuration some of the concerns for noise over a pure mono is also diminished.alla the figure 8 mono wind config.as you may well know,yourself.
Regards Rov

[detectormods]

I have tested a couple of dual field coils and found that you do not get something for nothing. A single wound coil will allow a maximum field at a set distance from the coil for a specific sized object that is optimized for the size coil.

When the coil is split into 2 windings, say one smaller then the distance the initial sized object was detected will reduce, the coil will give an improved response on a smaller object. Multi series coils only shift the balance on size and depth. They may increase ground noise but i would need to carry out some experiments to prove or disprove the theory.

[Rov]

WM6,the few coils made are all in the field in use,by others already.I must wait for their return.but I suspect they will be purchased by the users that have them already,from the brief reports back to me.I could make more,but takes time for me to obtain the coil shells from the US.I have no stock of these left.I appreciate your interest.
Mechanic,wire is silverplated multistrand teflon coated.high temp. spec.made by Belden.I purchased in minimum 300m rolls. the percieved response time over targets is faster an has a crisper feel to it,over other multistrand tin plated wires ive used.an the rise an settle time for the coil on switch on is fast.especially noticeable on the SD/GP series of PI detectors.I will have to Scope an document this carefully to confirm conclusively.On my Pulsemate PI they work well also.
As interest Ive used Aluminium wires also,an this wire offers some interesting characteristics.in solid enamelled,not a multistrand.(which i cant find)
regards Rov

[Mechanic]

Hi Rov,

I think it would be worth still looking into the dual field coils. Whites cannot patent all methods of making a dual field. If that could be done minelab would have done it for coils and detectors. I think that as long as the method for building and specifications are different to the whites coils, there should not be a problem.

Is the wire you used silver plated litz?

Cheers Mick

[Aziz]

Interesting coil

Look at the heavy duty coil wire of this patent application:
http://www.freepatentsonline.com/3601691.pdf

It is made of a metal strip wound spiral in the coil housing.

Aziz

[Aziz]

Hi Moodz,

I am getting tired, to read the entire patent paper. Last times, I look at the pictures and read the claims only.

"A plurality of coils":
Well, a spiral coil is one. It has as many coils as it has windings.

Aziz

[Qiaozhi]

Rick, be aware that White's has a patent pending on dual field coils.

- Carl

Just to make things clear here:
When the term "Dual Field Coils" is used, I assume this refers to the case where the outer and inner coils are in series, and are used in the same way as a mono coil ... and does not refer to the usual IB coil arrangement. I think this needs to be clarified, as there appears to be some confusion here.

[Aziz]

Well,

White's have to give the proof of pending patent for a dual field coil. I did not find the patent in the data base yet. I found a two-box solution from Garret (rectangular and a smaller circular coil) only.

As long as the proof is not given, we can assume that it is not protected.

BTW, I have been using dual PI coils in my school time (1980..1990) already.

Aziz

[WM6]

T

the small quantity produced to date have not been commercially sold.only distributed to hobbiests/enthusiasts for personal testing an appraisal,

Hi Rov

I am interesting to test one and of course to give you noncommercial compensation for the costs and your work in it.

Regards

[moodz]

Are the patent examiners dumb?
Are the patent appliers dumb?
Are the patent appliers fooling us?
Or are we the patent readers stupid only?



Aziz

Most patent examiners are not experts in specific technical fields like metal detecting though they may have knowledge of engineering principles ... they are experts in determining whether the claims are sufficiently different in a legal perspective from prior art or existing patents. Since they dont build the device you are claiming they have absolutely no clue if the device actually works ( or can even be built ). So legally they are smart but technically dumb. ( for example in science you cannot make a claim unless someone CAN duplicate your results )

The patent appliers think that they are protecting their IP however it is very expensive to lodge a patent, secondly to determine if someone might be infringing your patent and then to try and sue them. Best left to large corporations. For a small person .. patents are a waste of your valuable development time.

The patent appliers are trying to fool us partly because the patent is not written like a set of instructions on how to build the device and partly because the appliers make wild claims using terms like 'a plurality of coils' but then describe the 'preferred embodiment' which only uses one coil .... go figure. Not to mention all the hand drawn diagrams like in patent 7649356 with no time base / amplitude or indication how they were generated.

The patent readers are stupid because under the research exemption clause for patents hobbyists should read more patents ... most of the time they mistakenly believe they have to come up with their own solutions ... and most of the time reinventing the wheel or even going backwards. If you knew everything that had been patented in a certain field you would be more sure of not going over old ground and coming up with new ideas.

MooDz

[Rov]

I havent back engineered anybody elses commercial manufactured coil to produce my own,it was quite a bit of work to perfect on my own a twin loop to work successfully ,getting suitable wires,testing ,winding,inductances right an achieve a low ohms,that a lot of PI machines will see an drive Ok.Maybe I just call it something else a Duo Loop or whatever?
Yes Aziz I can make a tri loop coil.I have the recipe for the electrical characteristics required.Will give this a go.Then I suppose that somebody may suggest Ive harvested the idea from Garretts on some 3 loop imaging coil or something.
Ive still got a couple hundred meters of lovely silverplated multistrand teflon (yes very expensive wire)to use for something.Best use it up an see what I can come up with.
regards Rov

[Aziz]

Who is more fool?

...( half the time the patent description is wrong and does not describe the manufactured item anyway )
MooDz

Are the patent examiners dumb?
Are the patent appliers dumb?
Are the patent appliers fooling us?
Or are we the patent readers stupid only?



Aziz

[Carl-NC]

I'm at home today and don't have the application number, and for some reason it's not a published application.

I'm sure White's would not bother with home-hobbyist infringements, and may even be interested in allowing 3rd-party developments.