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Detector Technology and Electronics and new detectors => Detector Coils => Topic started by: Doug on Friday April 24 2015 20:38:03 AEST PM



Title: How can all of this be achieved with a mono coil?
Post by: Doug on Friday April 24 2015 20:38:03 AEST PM
How can all of this be achieved with a mono coil?
Coiltek are coming out with a new 14” mono  next week that they claim (and some who have tested prototypes see to confirm) that will have very significantly improved sensitivity and depth  to small gold in particular. The coil is apparently quite heavy which suggest more windings= higher tx field strength In view of the fact that ML detectors need coils with a inductance of about 300uH and a low  resistance how can all of this be achieved in this new mono as the inductance increases as the square of the number of turns? L= (d^2 * n^2)/(18d+40l)  for an air core inductor? If the coil has more windings its efficiency as an antenna will also be improved  including to EMI and ground mineralization?The coil its reported still uses litz wire.
L is inductance in micro Henrys,
d is coil diameter in inches,
l  is coil length in inches, and
n is number of turns.
http://www.pronine.ca/coilcal.htm
http://info.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html
http://lcbsystems.com/InduCalc.html
Ideas?
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: Prospector_Al on Saturday April 25 2015 04:19:48 AEST AM
Hi Doug,

It may be a mono coil in name only. 

There's a simple way to decrease the sampling delay.  It's an old idea that was used in the military
mine detectors.  Only the firing pin is metallic and to detect it, the sampling pulse must get very
 close to the trailing end of the coil pulse.

It's the inductance of the receiving coil that determines the required sampling delay. As you point
out, the inductance is proportional to the square of the turns.  The target signal amplitude however,
is proportional to the turns.

Therefore, two smaller cois with the same total number of turns and the same total area yield the
same signal amplitude with only half the inductance.  (The interaction between the coils modifies
that a little.)  This increases the sensitivity to targets with short time constants, but leaves the
sensitivity to large, solid targets unchanged.  Isn't this what we're seeing with the ZED?

"Everything old is new again..."

Prospector_Al


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Saturday April 25 2015 10:54:33 AEST AM
  
Hi Doug,

It may be a mono coil in name only.  

There's a simple way to decrease the sampling delay.  It's an old idea that was used in the military
mine detectors.  Only the firing pin is metallic and to detect it, the sampling pulse must get very
 close to the trailing end of the coil pulse.

It's the inductance of the receiving coil that determines the required sampling delay. As you point
out, the inductance is proportional to the square of the turns.  The target signal amplitude however,
is proportional to the turns.

Therefore, two smaller cois with the same total number of turns and the same total area yield the
same signal amplitude with only half the inductance.  (The interaction between the coils modifies
that a little.)  This increases the sensitivity to targets with short time constants, but leaves the
sensitivity to large, solid targets unchanged.  Isn't this what we're seeing with the ZED?

"Everything old is new again..."

Prospector_Al

Thanks. Your explanation may explain why the new coil is apparently so much heavier. You are right about the ZED! It appears to give no more depth than previous models on long TC nuggets!
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Saturday April 25 2015 11:12:42 AEST AM
The in - ground depths on short TC targets that I have read on other forums that the GPZ is producing far exceeds the air - testing results that I have done with my GPX and Mono coils on small nuggets.

Such in- ground depths as 0.6 gram nugget at 13 inches and 3.5 gram specie at 20 inches both said to be measured and dug carefully.

Also spoke to someone by phone whose friend dug a 3 gram nugget at 19 inches, again said to be dug and measured carefully.


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Saturday April 25 2015 11:19:57 AEST AM
  
The in - ground depths on short TC targets that I have read on other forums that the GPZ is producing far exceeds the air - testing results that I have done with my GPX and Mono coils on small nuggets.

Such in- ground depths as 0.6 gram nugget at 13 inches and 3.5 gram specie at 20 inches both said to be measured and dug carefully.

Also spoke to someone by phone whose friend dug a 3 gram nugget at 19 inches, again said to be dug and measured carefully.

I  thought i read on 4 umer that the .6 grams at 13" was using a prototype  coiltek elite mono?
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Saturday April 25 2015 11:26:39 AEST AM
  
I  thought i read on 4 umer that the .6 grams at 13" was using a prototype  coiltek elite mono?
doug ::419::

It was mentioned in the thread GPZ my rating 4 out 10 on that forum.


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Saturday April 25 2015 12:19:08 AEST PM
Going by some in-ground tests with a GPZ, which as I recall were posted here and on other forums, showed it detected a 0.7 gram nugget at 7.5 inches and a 3.5 gram nugget at 12 inches.

These depths are nearer to what I can achieve in an air-test on a 0.8 gram and a 4 gram nugget with my GPX and a 12 inch mono coil.

Nuggets and Species can vary greatly in shape, purity and surface area but the in-ground depths being stated by others with a GPZ are significantly above the GPZ in-ground test results that I am speaking about.

I very much doubt the new Coiltek 14" Mono coil on a GPX will make up the difference on small nuggets if we are to  believe the in -ground depths being stated by owners of a GPZ with its 14" DOD coil.

However if the in- ground depths in the test results I speak about in my first sentence of this post, are closer to the what the GPZ can achieve, then maybe a new type of mono coil can create more depth for the owner of a GPX and get closer to the GPZ on smaller nuggets.

Edited due to Spelling Errors


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Saturday April 25 2015 12:35:46 AEST PM
  
Going by the some in-ground tests with a GPZ, which as I recall were posted here and on other forums, showed it detected a 0.7 gram nugget at 7.5 inches and a 3.5 gram nugget at 12 inches.

These depths are near to what I can achieve in an air-test on a 0.8 gram and a 4 gram nugget with my GPX and a 12 inch mono coil.

Nuggets and Species can vary greatly in shape, purity and surface area but the in-ground depths being stated by others with a GPZ are significantly above the GPZ in-ground test results that I am speaking about.

I very much doubt the new Coiltek 14" Mono coil on a GPX will make up the difference on small nuggets if we are to  believe the in -ground depths being stated by owners of a GPZ with its 14" DOD coil.

However if the in- ground depths in the test results I speak about in my first sentence of this post,are closing to the what the GPZ can achieve, than maybe a new type of mono coil can create more depth for the owner of a GPX and get closer to the GPZ on smaller nuggets.

Thanks for the clarification. However you do not need a special mono coil to have sensitivity to small  gold. I know of an experimental Pi detector that can sample at 10 usecs with an 18" NF mono at a peak coil current of about 3.5 amps and detect a .2 gram nugget at several inches in air tests and  detect some longer TC targets beyond the range of the gp/gpx!
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Saturday April 25 2015 15:52:47 AEST PM
  
  
Going by the some in-ground tests with a GPZ, which as I recall were posted here and on other forums, showed it detected a 0.7 gram nugget at 7.5 inches and a 3.5 gram nugget at 12 inches.

These depths are near to what I can achieve in an air-test on a 0.8 gram and a 4 gram nugget with my GPX and a 12 inch mono coil.

Nuggets and Species can vary greatly in shape, purity and surface area but the in-ground depths being stated by others with a GPZ are significantly above the GPZ in-ground test results that I am speaking about.

I very much doubt the new Coiltek 14" Mono coil on a GPX will make up the difference on small nuggets if we are to  believe the in -ground depths being stated by owners of a GPZ with its 14" DOD coil.

However if the in- ground depths in the test results I speak about in my first sentence of this post,are closing to the what the GPZ can achieve, than maybe a new type of mono coil can create more depth for the owner of a GPX and get closer to the GPZ on smaller nuggets.

Thanks for the clarification. However you do not need a special mono coil to have sensitivity to small  gold. I know of an experimental Pi detector that can sample at 10 usecs with an 18" NF mono at a peak coil current of about 3.5 amps and detect a .2 gram nugget at several inches in air tests and  detect some longer TC targets beyond the range of the gp/gpx!
doug ::419::

A .08 gram "nugget" can be detected at 2"-3" and a 5 cent piece at roughly 17"-18"
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Saturday April 25 2015 16:31:49 AEST PM
  
I A .08 gram "nugget" can be detected at 2"-3" and a 5 cent piece at roughly 17"-18"
doug ::419::

Goodness are these results with an 18" mono on this said experimental detector?


Title: Re: How can all of this be achieved with a mono coil?
Post by: IBGold on Saturday April 25 2015 17:02:52 AEST PM
::62:: This sounds like an Eric Foster stacked coil to me we have been testing this coil of late and my inital findings are very impresive but I have yet to try it with a minelab detector. ::62::


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Saturday April 25 2015 17:08:54 AEST PM
  
  
I A .08 gram "nugget" can be detected at 2"-3" and a 5 cent piece at roughly 17"-18"
doug ::419::

Goodness are these results with an 18" mono on this said experimental detector?

Yes.
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: bugwhiskers on Saturday April 25 2015 17:11:56 AEST PM
Eric Foster has made monumental contributions to "the art".


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Saturday April 25 2015 17:15:23 AEST PM
  
::62:: This sounds like an Eric Foster stacked coil to me we have been testing this coil of late and my inital findings are very impresive but I have yet to try it with a minelab detector. ::62::

IBGold if you ever want another independent tester to test a coil of yours let me know and I would be privileged to do so on my GPX5000.


Title: Re: How can all of this be achieved with a mono coil?
Post by: GARY on Sunday April 26 2015 11:00:52 AEST AM
  
::62:: This sounds like an Eric Foster stacked coil to me we have been testing this coil of late and my inital findings are very impresive but I have yet to try it with a minelab detector. ::62::

Maybe a stacked Coaxial coil which I have read Eric say has less ground feedback than a mono since the TX coil is separated by a vertical distance from the bottom RX, which is close to the ground as the surface mineralisation that gives the greatest signal variations with coil type.

Eric says mineralisation at depth (6in or more down) gives less change in signal between coil types. Also he says increasing the separation in a Coaxial coil will reduce ground effect, and also the signal, as the TX gets further away. The signal from a small object will decrease faster than the ground so there is no advantage here.

Therefore I assume the vertical separation distance between the Tx and Rx coil is most important to retain sensitivity to small nuggets but what effect on larger nuggets?


Title: Re: How can all of this be achieved with a mono coil?
Post by: Doug on Monday April 27 2015 11:11:16 AEST AM
 On another forum its speculated that the  Coiltek elite coil uses braided litz wire like the 7000 DOD Tx.
doug ::419::


Title: Re: How can all of this be achieved with a mono coil?
Post by: 1anSDC on Wednesday June 24 2015 08:33:44 AEST AM
I have one of the new CoilTek 14" Elite Mono coils and am interested to know if it is "new technology".

It certainly is sensitive and I just yesterday picked up a single shotgun pellet at about 2" at Mt Crawford. I also dug a foil pouch out of newly turned soil for tree planting, down past 2 feet. The coil picked up the pouch when waved a well above the surface of the soil. Ever hopeful one day these massive signals will materialise into a large nugget  ::62::

It gives nice sharp responses and behaves a lot like a smaller coil on steroids. I have noticed and it has also been pointed out to me by others that the left side of the coil is a little more sensitive than the RHS. It also has a sensitive "toe" and "heel" hot spot for testing your recovered target over.

Anyone yet know if its 2 smaller coils acting as one as has been suggested above?

Ian


Title: Re: How can all of this be achieved with a mono coil?
Post by: greylourie on Thursday June 25 2015 06:38:40 AEST AM
  
Maybe a stacked Coaxial coil which I have read Eric say has less ground feedback than a mono since the TX coil is separated by a vertical distance from the bottom RX, which is close to the ground as the surface mineralisation that gives the greatest signal variations with coil type.

Eric says mineralisation at depth (6in or more down) gives less change in signal between coil types. Also he says increasing the separation in a Coaxial coil will reduce ground effect, and also the signal, as the TX gets further away. The signal from a small object will decrease faster than the ground so there is no advantage here.

Therefore I assume the vertical separation distance between the Tx and Rx coil is most important to retain sensitivity to small nuggets but what effect on larger nuggets?

Maybe this is a stupid question, but what if the tx power can be reduced or tailored for a particular ground ? Couldn't you in theory get better signal returns ?

Also on other comments in this thread, Razorback make folded monos which display good pinpointing in the toe of the coil.
And I have read sdc users mentioning pinpointing with the sdc coil, something about the 11 o'clock position....
Also recently read something about the new coil, where it was felt sensitivity was greatest on the side opposite the cable gland/exit.


Title: Re: How can all of this be achieved with a mono coil?
Post by: greylourie on Thursday June 25 2015 07:04:17 AEST AM
Aziz did a lot of work to show with tables and his coil software, how to make better mono coils.

Theres a whole lot of info and graphic illustrations. Heres a couple of links to that thread.

http://australianelectronicgoldprospectingforum.com/general-chat-and-discussion-forum/the-latest-stab-in-the-dark-by-the-patent-parrot!/msg32055/#msg32055

http://australianelectronicgoldprospectingforum.com/general-chat-and-discussion-forum/the-latest-stab-in-the-dark-by-the-patent-parrot!/msg32076/#msg32076


Title: Re: How can all of this be achieved with a mono coil?
Post by: greylourie on Thursday June 25 2015 20:56:58 AEST PM
And Stefan spoke about reducing capacitance in coils, even earlier in time. Here is a quote from him...

" I place 4 turns on the first layer then place a spacer and then wind another 4 turns etc. This way you get a rectangular coil. The reason for the spacer is to minimise the interwinding capacitance between the layers."

His full post on this can be found here : http://www.geotech1.com/forums/showthread.php?13124-Mono-Coil-construction-help&p=54940#post54940


Title: Re: How can all of this be achieved with a mono coil?
Post by: 1anSDC on Sunday June 28 2015 10:40:26 AEST AM
Interesting info, thanks GL!

I am relatively new to using PI machines but have a tech background in electrical/electronics, and find the tech side of prospecting just as interesting as finding nuggets. Now I find myself needing to know more and the geology of gold bearing ground and stuff like what makes a good coil even better. Its an interesting hobby and now that I'm retired its also a great form of exercise. Whats not to like?

Ian


Title: Re: How can all of this be achieved with a mono coil?
Post by: 1anSDC on Wednesday July 1 2015 20:36:00 AEST PM
I spoke by phone with CoilTek today about their "new technology" in the 14" Elite Mono and discovered the following.

It is new tech being used, (based on established theory) by them for the first time in manufacturing this coil. The new mono coil is still a single coil, but is now wound in such a manner as to align the coil's field strongly vertical. Horizontal field spread from the edge of the coil has been reduced and the increased vertical field provides the better depth and sensitivity that is being noted and measured by those using the coil.

Its finally nice to know that the increased depth and sensitivity provided by this new coil has sound science behind it and not just the camo paint job! CoilTek indicated to me that the method used in winding this coil and the type of coil that results is suitable for some other size coils but not all. Nice to see innovative products still being introduced for the GPX, etc detectors.

Its also interesting to note that after CoilTek released their new 14" Elite to market that NF started making it known they were working on a similar coil. Strange how that happens and probably just coincidence but I guess you can never get too much of a good thing  ::419::

Ian


Title: Re: How can all of this be achieved with a mono coil?
Post by: greylourie on Wednesday July 1 2015 21:59:55 AEST PM
Hi Ian,

In those links to Azizs posts that I made earlier on in this thread.
Aziz shows how varying the pattern of layering/wraps can be beneficial. Especially compared to just plain old bundle winding.

Imagine a coil with a fixed number of turns of wire. You could adjust the profile of the finished bundle so that the coil bundle profile is wider... facing the target/ground.  Like a wider fishing net, so to speak. A a slightly more rectangular one, compared to square profile.

I think Stefan, IBGold and authere have been experimenting with coil-building and found out a lot of interesting things, empirically, over the years.

Aziz  used maths and his coil software to demonstrate some of these things.

The fact is that manufacturers are going to closely guard their methods, for obvious commercial reasons.

Thats why we should be grateful for forum hosts and forum posters who are willing to share. Unfortunately some just leach and try turn what they have learned into a quick buck, or a patent......

Fact is most of what we can buy today is just a mix and mash and finely tuned rehash of age old principles.


Title: Re: How can all of this be achieved with a mono coil?
Post by: Aziz on Sunday November 26 2017 07:35:13 AEDT AM
Bang! ::620::

Hi guys,

Regarding this discussion:
http://golddetecting.4umer.net/t22007-are-coiltek-nf-using-new-mono-coil-technology

You know who copied from whom!
My coil software knows the exact answer:
both have copied from ....
::620::
Aziz


Title: Re: How can all of this be achieved with a mono coil?
Post by: Aziz on Tuesday November 28 2017 19:53:52 AEDT PM
Hi all,

I'm just wondering, why it took so long time to implement the results of the coil analysis we made a few years ago.
Anyway, better late than never!
;-)
Aziz