Dual Field Pi Coils

[mel parker]

Dual Field Coils

I have obtained a Whites Dual Field detector without a coil. Where can I get one of your coils? Thanks Mel Parker

[Rov]

Hi Mel,Ive replied to your message,check your details.I may be able to help you.
Rov

[Darp]

What really is a Dual Field Coil?

I have trying to find this out for days. Even people that have home built them do not feel comfortable to say how they work.

I have a TDI with one, its got a 12" outer and 6" inner. Is it acting as two separate coils, alternating a inner send and receive with an outer send and receive to same coil, or is one sending and the other receiving?

Thanks in advance for any info how they work and what their purpose/advantage is.

Cheers

[Rov]

Yes they act as two seperate coils with broader and also more refined depth of field on targets.imagine two distinct cones of magnetic field penetrate the ground and highlight your target.one broader and deeper the other more refined and smaller for closer smaller targets.you miss less targets overall.good design.and a pleasure to use.

[Darp]

ROV,

Thanks.

If you can add some detail to that then think I can finally feel understand it. What you have said is in line with my guess

On the send signal if we can refine that a little bit. Do (A) both coils fire at same time (that would tend to cause interference with each other it would seem) or do (B) they alternate, big one fires and receives at big coil, then small one sends and receives?

B makes more sense to me so in effect the user has two coils acting independent to give user best of both the big and small size. Is that correct?


Thanks!

[Rov]

Yes,your thinking is correct.but as a coil builder myself,I dont wish to elaberate on any proprietry technique or properties,as you can understand.Whites and Other have there developed technique for signal Tx and Rx with Dual Field coils.
Suggest to experiment yourself if you have a TDI,an can build a simple DF coil,within spec.is not too hard,and you will see.
Maybe others here can add more to the topic,than I wish to atm.
regards Rov

[WM6]

ROV,


B makes more sense to me so in effect the user has two coils acting independent to give user best of both the big and small size. Is that correct?


Thanks!

Two coil act more like spiral coils, so not realy independent, but as mono coil with intentionaly distributed/shaped EM field in a way that act near like two independent coil used at same time. Mean such coil is sensitive on shallow small target and at the same time on deeper bigger target.

You can experimet with such coil, but for start: you use for inner coil 1/2 of outer coil diameter and for each coil 1/2 of total (mono) coil inductance. Turns of both coil must continue (and to be interconnected) in the same direction (not in oposite - because of mutually negating).

Look at this Aziz post:

http://www.geotech1.com/forums/showp...1&postcount=28

[Darp]

Interesting. So I was off. It is both inner and outer firing and receiving at same time.

Guess it is possible that under some circumstances the inner and outer might pick up a signal from the other that the originator does not pick up.

From what you two have said the coils would be in series, which is simple.

Thanks, am learning.

Cheers

[Darp]

Parallel, pic

Have seen a pic by Ism on TDI Forum http://img443.imageshack.us/i/dfcoil002.gif


He built this for his TDI and it looks like parallel wiring, which means the two coils need to be matched resistance wise fairly close. So both fired in parallel is now my best guess. It helps to know this when using my TDI and thinking of mods to the technology.

Thanks to all for your help on understanding this.

Cheers

[Darp]

Actually Ism says its in Series.

[Rov]

Darp,make a 11 1/2 inch loop with 16turns of medium duty tin plated multistrand wire. will give you about 0.4ohms coil resistance.
next make a 6 inch loop for inner with 19 turns medium duty tin plated multistrand wire. this will give you about 0.4ohms coil resistance also.
wire these two coils in Series with each other,an now you will have a very deadly coil to use on your TDI or other PI machines.
Regards Rov

[Rov]

Bump! thanks for your private emails,It works very well for you.
Regards Rov

[Sean_Goddard]

The USPO is so overworked they don't even bother checking anymore. I've seen many, many beeper patents which are so similar they should never have been granted in the first place.

Only recently I supplied White's with information which helped them nullify one of Minelabs as they had prior knowledge of the alleged infringment based on one of MY designs back in 2002 (some FOUR years+ before ML filed (HAHAHA UP YOURS LAMEBIN - now you know who STUFFED YOU)!!

Consider that patents were ORIGINALLY designed NOT for protection, but for dissemination of information.

If you want a real laugh, look at some of the patents applied for from Japan, they're absolutely stupid in about 90% of cases, looks like the USPO are granting anything in patents now too.

I heard of one guy who took an existing patent, an applied for it under his OWN name, he was about to be granted it when he 'fessed up an told the USPO what he'd done. I imagine they were pretty nonplussed with that, their fault though I think.

To sum up, just because a company hold a patent doesn't mean the contents of that patent are of any REAL world worth OR indeed that the patent is valid (like most of Limebans for example - ).

I'm pretty sure there are many examples of patents which are VERY similar to work done by others who never bothered to patent because of the costs involved. Not everyone has $10K+ lying around unless they are a big business, and not everyone NEEDS to protect their work, especially like a LOT of the work done on this forum where we share.

Magnetic analysis software and CHEAP too!! http://www.vizimag.com/ordering.htm

[Sean_Goddard]

OK, maybe I'm missing the point here, take a look at the two analyses of my interpretation of a DF coil, I don't see ANY benefit over a single field, although in theory DF SOUNDS like it would be a good idea.

Maybe my analysis is wrong but from what I see as an output, DF is just a marketing gimmick and I do NOT expect this from Whites as I thought they were above that sort of thing.

Can't say I was impressed with the TDI though. Spectra V3..now THAT'S a WHOLE different ball game.. VERY nice!!

[WM6]

Can't say I was impressed with the TDI though. Spectra V3..now THAT'S a WHOLE different ball game.. VERY nice!!

Probably you are one more impressed by user interface.

Did you done comparative tests between mono and dual field coils or you only theoretize here?