northwest The need for big deep gold detectors.
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australian electronic gold prospecting forum.com  |  Detector Technology and Electronics and new detectors  |  Detector Coils (Moderator: Goldman)  |  Topic: The need for big deep gold detectors. 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: The need for big deep gold detectors.  (Read 28570 times)
Muntari
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« Reply #680 on: Sunday March 11 2018 00:06:23 AEDT AM »

  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi Autitch,

Indeed, that coil lead and the bundle wound coils are not helping Cp at all.
Are theses coils well used?

Cheers

Muntari

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« Reply #681 on: Sunday March 11 2018 00:14:49 AEDT AM »

  
  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi Autitch,

Indeed, that coil lead and the bundle wound coils are not helping Cp at all.
Are theses coils well used?

Cheers

Muntari



Muntari

I purchased the coils second  hand and I  have  never used them.  They are used  but in good  condition. 
AuTitch
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Muntari
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« Reply #682 on: Sunday March 11 2018 00:20:54 AEDT AM »

  
  
Hi Autitch,

In test 1 I noticed the TX resistance is 0.57 Ohms is that a typo?

Btw, it's good you have include your test circuit, also noticed your using the DE-5000.
There is a number of members here that have them now so it's good for comparing notes.
I'll stick with using mine too instead of the Agilent just for clarity.

Cheers

Muntari

I have checked my notes and the TX resistance was definitely 0.57 Ohms.

I have a second Coiltek DD 14" coil that may get sacrificed and that too measures 0.56 Ohms.

Autitch

Autitch
 

Hi Autitch,

I was thinking its a little weird with that TX resistance in test 1 unless I'm missing something,
Umm yes I missed the obvious, lead resistance, just re read your post and noticed the short enamelled wires were used in some tests...must be my bed time

Thanks for posting the table format, great job  happy face

Cheers

Muntari

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Muntari
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« Reply #683 on: Sunday March 11 2018 00:25:51 AEDT AM »



Thanks Autitch, was just wondering, anyways hope you find some gold with them


Cheers

Muntari
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Eski
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« Reply #684 on: Monday March 12 2018 18:37:18 AEDT PM »

Hi guys , not sure if it helps :

there is a foam product that has low pressure expansion, we use it around window frames in home building...

it works like an adhesive  but will not warp things.

touch'n'seal no-warp foam window and door insulating sealant.
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Muntari
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« Reply #685 on: Monday March 12 2018 20:36:04 AEDT PM »

  
Hi guys , not sure if it helps :

there is a foam product that has low pressure expansion, we use it around window frames in home building...

it works like an adhesive  but will not warp things.

touch'n'seal no-warp foam window and door insulating sealant.

Hi Eski,

Thanks for the info, will check it out

Cheers

Muntari
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« Reply #686 on: Monday March 12 2018 21:29:52 AEDT PM »

I need to replace some putty around a window is it any good for that ?, I can only find touch'n'seal  on ebay @ $38 a tube
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Aziz
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« Reply #687 on: Monday March 12 2018 21:50:57 AEDT PM »

  
I’ve put the numbers in a table with calculated capacitance from the SRF measurements.
There are some primary observations one can make from these measurements.
1. The coax parameters has a very large impact on the capacitance of the coil TX and a significant affect on the RX capacitance.
2. The RX interwinding capacitance is very large.
3. The shielding contribution to the capacitance of either the TX or RX is negligible.
4. The RX SRF is well below the 500 kHz figure that is consider optimum.

AuTitch


Hi AuTitch,

thanks for your time and effort doing this measurement.
It is quite interesting.

Aziz
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« Reply #688 on: Tuesday March 13 2018 00:04:31 AEDT AM »

Hi All,

Didn't have much time to do any work on the 18 inch coil this weekend but just enough time to revisit the spiral wound former using XPS.

Last time I tried with a 1mm bit it ripped the material and no matter what I tried, it just wouldn't work for me.

Now when I used the hot wire cutter to trim down the 30mm sheets of XPS i noticed different thickness of "skin" forming after  melting depending on the speed of the material passing through the hot wire. Eg..the slower it was fed the thicker the skin.
So it had me thinking...I grabbed a bit of scrap XPS and fed it through the hot wire cutter slowly then put the CNC to work to machine the same spiral pattern as per my original 200mm test coils and this time it machined Ok. I then passed the hot wire cutter over it once more just skimming the surface and it strengthened the XPS.
Just what I was looking for. I didn't bother cleaning it up much so looks rough but it works

I wound some 0.38mm enameled copper wire onto it, Inductance was same as original (99 uH)  SRF = 4.26MHz (originals were around 4.1 to 4.4).
So I might play with it a bit more when I get time, its worth it due to the weight saving.

I'm still trying to source some Sikabond foam fix from Bunnings they were out of stock at my local so its holding up the final assembly of the 18 inch coil

More later

Cheers

Muntari




* XPS 200mm former testJPG.JPG (107.17 KB, 480x640 - viewed 258 times.)
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« Reply #689 on: Tuesday March 13 2018 19:11:00 AEDT PM »

Hi all,

I have ordered the digital LCR/ESR meter PeakTech 2170 and it should arrive soon.
It is high time to own one.
 excited
Aziz
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« Reply #690 on: Tuesday March 13 2018 21:47:42 AEDT PM »

Muntari,  Bunnings Mile End Has it was there today just got home did you get my PM.

Regards, Ian. happy face
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Muntari
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« Reply #691 on: Tuesday March 13 2018 23:55:35 AEDT PM »

  
Muntari,  Bunnings Mile End Has it was there today just got home did you get my PM.

Regards, Ian. happy face

Hi Ian,

Thanks for that , yeah I noticed Munno Para have it too now.
Yep, just read you PM and responded, sorry missed it earlier
I've been busy rebuilding a larger vacuum former

Cheers

Muntari
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Muntari
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« Reply #692 on: Tuesday March 13 2018 23:57:47 AEDT PM »

  
Hi all,

I have ordered the digital LCR/ESR meter PeakTech 2170 and it should arrive soon.
It is high time to own one.
 excited
Aziz

Good stuff Aziz, yes it is  happy face

Cheers

Muntari
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« Reply #693 on: Wednesday March 14 2018 14:40:17 AEDT PM »

Hi Doug,

I have been thinking, perhaps we could have another thread for tools or methods related to coil building rather than me clutter up this thread, not sure?

Cheers

Muntari
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« Reply #694 on: Thursday March 15 2018 23:09:06 AEDT PM »

Hi all,

I will get my new LCR meter very likely tomorrow. It is on the way. I hope to speed up the development a bit then.
But I will work on a new PI design, which will exploit the new possibilities of the new coil design.
Main goal will be to reduce the ground noise effects and hence to minimize the detection hole and to increase the target response.
By sensing the coil coupling coefficient factor change (TX -> RX) a lot of ground noise effects in the off-time sampling time can be removed without decreasing the target response.

Cheers,
Aziz
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Muntari
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« Reply #695 on: Thursday March 15 2018 23:38:16 AEDT PM »

Hi Aziz,
That's great news, they are certainly handy to have around.
It will be interesting to see what new PI design ideas you come up with too, that would fully exploit the coil benefits as you see them.

Cheers

Muntari


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« Reply #696 on: Friday March 16 2018 18:27:23 AEDT PM »

  
I need to replace some putty around a window is it any good for that ?, I can only find touch'n'seal  on ebay @ $38 a tube

na... no good for that!
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« Reply #697 on: Friday March 16 2018 23:26:07 AEDT PM »

Hi all,

my digital LCR/ESR meter PeakTech 2170 came today. I'm really happy with it.  excited
A lot of interesting measurements will be made in the coming days/weeks.

My coil software must be adapted & arranged to calculate more accurate. The spiral/spider coil arrangement is causing non neglectable error in inductance/induction calculation as there are to many wires in the calculation region (thin/thick wire model, magnetic field inside the wire, induction inside the wire, etc., a typical boundary case problem). I have to redesign some of the core implementations. Unfortunately, this is not so trivial.

But my sound card LCR meter is pretty darn accurate when calibrated properly. Didn't know it until I compared my measurements with the 2170 LCR meter. The inductance calculation was inaccurate due to the described facts above.


Cheers,
Aziz
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« Reply #698 on: Saturday March 17 2018 00:40:12 AEDT AM »

Hi Aziz,

Great stuff, glad you have it and you are happy with it.
Will you be prototyping some more coils?

Cheers

Muntari
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« Reply #699 on: Saturday March 17 2018 01:00:25 AEDT AM »

  
Hi Aziz,

Great stuff, glad you have it and you are happy with it.
Will you be prototyping some more coils?

Cheers
Muntari

Yes, but when I have solved the issues and upgraded my coil software. It's a time consuming stuff and I have to read the electromagnetics stuff once again.

But interesting finding regards to litz/magnet wire, which confused me during last weeks/month of making measurements:
The proximity effect isn't neglectable in bundle coils. The proximity effect is domination over skin effect even on litz wire and isn't neclegtable. Using litz wire in bundle coils is a waste of money. Hahaha  

But the proximity effect decreases on spiral/spider coils greatly and you can even use simple magnet wire. Haha, that's a great news. The skin effect is neglectable in this case.
 smile

Cheers,
Aziz
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australian electronic gold prospecting forum.com  |  Detector Technology and Electronics and new detectors  |  Detector Coils (Moderator: Goldman)  |  Topic: The need for big deep gold detectors. « previous next »
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