Advanced PI coils

[authere]

Hi Aziz,

Orientation of nuggets can cause problems, would four satelite coils each given a burst at a given repetition from the same control box and then the signal averaged...do any good

Why does the signal always go thru 1 coil constantly?

Ron

I know nothing of what you speak, but i am a practical man!!

PS:In a DD with four satelite RX coils the signal could be rotated between them to get an average!

PPS:Can the signal be diverted to seperate coils or not!!

[Aziz]

Hi Aziz
I have enjoyed your coil posts thanks
but you may find some people are still away on Christmas holidays and miss your dead line of one week.

Ok, dead line extended to 42 days.
Hey, its not critical. I just want you all do something. Magic inspiration takes some time.

Aziz

[6666]

Hi Aziz
I have enjoyed your coil posts thanks
but you may find some people are still away on Christmas holidays and miss your dead line of one week.

[Aziz]

Your Last Chance!!!

Ok guys,

this is your last chance ever! If you don't want to give or share your coil proposal to be investigated, you will never ever get the chance again. My coil software won't ever be available to you (I'm not selling it either). You have to write your own coil analyzing software then.

I want to finish this coil investigation project when there is no active contribution to it anymore. I have a lot of interesting projects and expriments in the pipeline and I won't switch back to coils when I'm busy with them.

I'll give you one week. Take it or leave it.

Cheers,
Aziz

[Ferric Toes]

Nice case for advocating short pulse, high repetition rate designs (as i did here time ago). Any TX longer than target TC is just a waste of power. Actually, anything longer than sample time is too, more or less. Power economy goes the same, 3 times shorter pulse, 9 times less energy stored, so 9 times higher PRF for same current consumption. Obvious way to go for “fast targets” at least.


Now, Eric, this forum is wonderful place for information exchange, and you are probably right man to ask a question, potentially saving many futile efforts and pointless work for us. So, here is one, in short, it this approach wort something, or it is just (another) monkey businesses?


Time ago, i did some tests using constant peak current drive and variable voltage TX (simple circuit based on UC 3845 + mosfet, sensing resistor in D, another UC for variable PSU, ~10-180V) in order to produce variable pulse width containing same energy release per pulse. It worked fine ( i built it into real detector, some prehistorical Garrett and used it for actual detecting, target “elimination” based on TX pulse widtht, not delay time), but eventually ended up as a target response test instrument. This, in combination with described 2wire flat coil gave me idea to utilize something similar for bipolar multiperiod pulsing. I built some prototype, worked, but never finished to complete design, never done on PCB, never left my workbench and field tested.


Idea like this: UC3525 based TX, two coil halves pulsed from 2 different voltages, of same polarity but opposed ends, producing net 0 flux (bipolar), one long pulse~ 50uS from battery, followed by short ~1.5uS from PSU, field in another direction. Idea is, long pulse will excite target and mineralization component, short pulse will give just mineralization signal, target weakly excited. Sampled with single sample per pulse, amplified in gated AC coupled and high pass filtered amplifier, diff. integrator will substract samples, effectively providing GB adjustment ability. I know all this is patented and commercially used long time before, but may look like excellent DIY detector project, not more complex than HHd for example. Electronics worked fine, but i have no idea how this can perform in real soil. Actually most our soils here don't need it, but this is 11000km away from .au, and only tested with some bag samples and ferrite.


So, what is your opinion on this, worth doing to complete machine, or worth just to be burred under worst ground for good?

Yes, keep at it. It is a sound idea and similar to what I am researching right now. I can't say more at the moment but from the tests I have done it should work well. One difference though is the two TX widths, mine are longer. What patents do you think might already cover this idea?

Where is 11,000km away from .au? Send private message if you like.

Eric.

[Tepco]

Nice case for advocating short pulse, high repetition rate designs (as i did here time ago). Any TX longer than target TC is just a waste of power. Actually, anything longer than sample time is too, more or less. Power economy goes the same, 3 times shorter pulse, 9 times less energy stored, so 9 times higher PRF for same current consumption. Obvious way to go for “fast targets” at least.


Now, Eric, this forum is wonderful place for information exchange, and you are probably right man to ask a question, potentially saving many futile efforts and pointless work for us. So, here is one, in short, it this approach wort something, or it is just (another) monkey businesses?


Time ago, i did some tests using constant peak current drive and variable voltage TX (simple circuit based on UC 3845 + mosfet, sensing resistor in D, another UC for variable PSU, ~10-180V) in order to produce variable pulse width containing same energy release per pulse. It worked fine ( i built it into real detector, some prehistorical Garrett and used it for actual detecting, target “elimination” based on TX pulse widtht, not delay time), but eventually ended up as a target response test instrument. This, in combination with described 2wire flat coil gave me idea to utilize something similar for bipolar multiperiod pulsing. I built some prototype, worked, but never finished to complete design, never done on PCB, never left my workbench and field tested.


Idea like this: UC3525 based TX, two coil halves pulsed from 2 different voltages, of same polarity but opposed ends, producing net 0 flux (bipolar), one long pulse~ 50uS from battery, followed by short ~1.5uS from PSU, field in another direction. Idea is, long pulse will excite target and mineralization component, short pulse will give just mineralization signal, target weakly excited. Sampled with single sample per pulse, amplified in gated AC coupled and high pass filtered amplifier, diff. integrator will substract samples, effectively providing GB adjustment ability. I know all this is patented and commercially used long time before, but may look like excellent DIY detector project, not more complex than HHd for example. Electronics worked fine, but i have no idea how this can perform in real soil. Actually most our soils here don't need it, but this is 11000km away from .au, and only tested with some bag samples and ferrite.


So, what is your opinion on this, worth doing to complete machine, or worth just to be burred under worst ground for good?

[Ferric Toes]

What TX pulse width was used to excite targets having such a long decay?

For the nugget tests I used a fairly low power TX but had a control that altered the TX width from 50uS all the way through to 1mS. It also dropped the pulse rate proportionally so that the current draw remained about the same. For long TCs you can see on a scope that the decay curve "fills out" as you advance beyond 1TC. In other words, if the TX is too short you are not fully exciting the fundamental mode exponential. Once you go above 4TCs width then additional gains are small, so a nugget with a decay of 1ms would be giving 95% of its potential signal with a TX width of 950uS.

Eric.

[Aziz]

Latest Coil Analysis Excel Table

This is the latest excel table of all coils (zipped archive file):
CoilComp5(CoilCMP2)-04.zip

Candy for you:
Flat spiral coil calculator (excel sheet)
Flat spiral coil calculator.zip

Cheers,
Aziz

[Aziz]

What's Left Over?

Hi guys,

what's left over to look for?
- Coil types/architectures?
- Interesting questions to be investigated?
- Interesting ideas?

Your wishes/questions/ideas are welcome. But it must be reasonable and may not cause huge work for me. The coil type/architecture must be fair comparable to the 10 inch round mono coil. Trivial coil types aren't worth to invest a lot of work.

Comeon, we can invent the WBCT together.
Yes we can.

Cheers,
Aziz

[Tepco]

What TX pulse width was used to excite targets having such a long decay?

[Ferric Toes]

Hi Eric,
Speaking of Australia, someone told me that when you were there, you measured the Tcs of som big nuggets. Do you have any idea of the Tc of a 30 oz. nugget? I'm interested in developing a Giant Nugget detector, usig the thyratrons I mentioned in a different thread...

Allan

Looking at the total decay down into the noise level, a 15oz nugget was 2mS. A 31oz nugget was obviously greater than 2ms but I was not able to measure it properly; I would guess 4mS. A 5oz nugget measured 700uS. These are nuggets from Victoria where the gold is very pure. A nugget from Western Australia would have more silver in the alloy which makes a big difference to the conductivity. Similar size WA nuggets to the above might have decay times that are 1/2 as long.

Eric.

[Tepco]

I tried similar coil, .75:1 and .66:1 shape, not optimal, 0.5:1 seems to be best, but not higher. Part in coil center of full spiral serves to no purpose at all, just unnecessarily adding more material and slowing down the coil.

[Aziz]

Flat Spiral 0.75 DU - 1.0 DU

Hi all,

I have added another flat spiral PI coil to the comparision. Spiral beginning at 0.75 diameter unit and ending at 1.0 diameter unit (10"). Turns count N=27-28 (somewhere between for 300 µH, N=27.1 internal, 0.4 mm thin wire this time due to recuded loop area). See, what comes out:

Coil Comparison (Calculated Response Ratio to Reference Coil)
© 2012 by Aziz Ögüt. All Rights Reserved. 11-Jan-2013
Reference Coil: 300 µH Round Mono Loop Coil
		10" Spiral PI Coil (0.5 DU .. 1.0 DU)	10" Spiral PI Coil (0.75 DU .. 1.0 DU)
Target Depth [inch]	Target Depth [cm]	Relation to Reference SNR compensated (9.7 % more EMI noise)	Relation to Reference SNR compensated (13 % more EMI noise)
1	2,5	3,007	1,334
2	5,1	3,949	2,112
3	7,6	3,085	1,962
4	10,2	2,433	1,759
5	12,7	2,034	1,609
6	15,2	1,783	1,501
7	17,8	1,618	1,423
8	20,3	1,504	1,366
9	22,9	1,424	1,323
10	25,4	1,365	1,291
11	27,9	1,320	1,266
12	30,5	1,286	1,246
13	33,0	1,259	1,230
14	35,6	1,237	1,217
15	38,1	1,219	1,207
16	40,6	1,205	1,198
17	43,2	1,193	1,191
18	45,7	1,183	1,184
19	48,3	1,174	1,179
20	50,8	1,167	1,175
21	53,3	1,161	1,171
22	55,9	1,155	1,167
23	58,4	1,150	1,164
24	61,0	1,146	1,162
25	63,5	1,142	1,159
26	66,0	1,139	1,157
27	68,6	1,136	1,155
28	71,1	1,133	1,154
29	73,7	1,131	1,152
30	76,2	1,129	1,151

We can conduct some important rule for a PI coil bundle:
Make it vertically thin and make it radially (horizontal) thick. It doesn't matter, when the coil bundle even gets radially quite thick. It's just an approximation of a spiral coil. You can fill the inner area with additional loops if you like. I don't see much difference. But we usually want to see through the center hole. Just leave some reasonable hole.

Another coil type: Rodin-Starship coil
Not optimal - forget it.


Cheers,
Aziz

[Prospector_Al]

There are some newer papers and dissertations related to human demining with thorough theoretical background. I even found some detailed analysis of ferrous targets. Hopefully it will enable me to tune up the spice target models for Fe.

Hi Eric,
Speaking of Australia, someone told me that when you were there, you measured the Tcs of som big nuggets. Do you have any idea of the Tc of a 30 oz. nugget? I'm interested in developing a Giant Nugget detector, usig the thyratrons I mentioned in a different thread...

Allan

[Aziz]

See What Happens

Hi all,

I have distributed the spiral coil over 20 mm thickness. There are 3 layers of spiral coil, each 10 mm co-axial apart. Total N=39 (13 each layer). We have more copper and more turns. This is causing 20.4% more EMI noise induction. So I have to compensate a lot. See what comes out:

Coil Comparison (Calculated Response Ratio to Reference Coil)
© 2012 by Aziz Ögüt. All Rights Reserved. 10-Jan-2013
Reference Coil: 300 µH Round Mono Loop Coil
		10" Spiral PI Coil (0.5 DU .. 1.0 DU)	10" Spiral PI Coil (0.5 DU .. 1.0 DU, 20mm thick, 3 spiral layers)
Target Depth [inch]	Target Depth [cm]	Relation to Reference SNR compensated (9.7 % more EMI noise)	Relation to Reference SNR compensated (20.4 % more EMI noise)
1	2,5	3,007	2,743
2	5,1	3,949	3,355
3	7,6	3,085	2,565
4	10,2	2,433	2,027
5	12,7	2,034	1,716
6	15,2	1,783	1,528
7	17,8	1,618	1,409
8	20,3	1,504	1,331
9	22,9	1,424	1,278
10	25,4	1,365	1,241
11	27,9	1,320	1,215
12	30,5	1,286	1,196
13	33,0	1,259	1,183
14	35,6	1,237	1,173
15	38,1	1,219	1,165
16	40,6	1,205	1,159
17	43,2	1,193	1,155
18	45,7	1,183	1,152
19	48,3	1,174	1,150
20	50,8	1,167	1,149
21	53,3	1,161	1,148
22	55,9	1,155	1,147
23	58,4	1,150	1,147
24	61,0	1,146	1,147
25	63,5	1,142	1,147
26	66,0	1,139	1,147
27	68,6	1,136	1,147
28	71,1	1,133	1,148
29	73,7	1,131	1,148
30	76,2	1,129	1,149

The near detection zone suffers. But is going slightly deeper (not significant). It's not a good idea, to separate the coil bundle in the co-axial direction/region. Better in the radial/concentric direction/region (like a thin/flat spiral).
BTW, one can see the accuracy of the latest relation: approx. +/-0.003

Cheers,
Aziz