Advanced PI coils

[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]

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

[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

[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

[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.

[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]

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.

[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

[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]

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

[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!!

[Davor]

How about a "lucky clover" complex coil. It would have 4 each Tx and within them at 0.9 radius 4 Rx coils, and phasing would be balanced. E.g., if observing circles as quadrants, Tx would be ++-- and Rx +-+-
It would be double balanced. Kind of "double bicycle".

[PATCHES JUNIOR]

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

Aziz

Thanks for giving everyone a chance Aziz!! That one week had everyone in a panic.

[Aziz]

How about a "lucky clover" complex coil. It would have 4 each Tx and within them at 0.9 radius 4 Rx coils, and phasing would be balanced. E.g., if observing circles as quadrants, Tx would be ++-- and Rx +-+-
It would be double balanced. Kind of "double bicycle".

Hi Davor,

could you provide a detailed sketch of the coil configuration? I don't understand your coil configuration.
Cheers,
Aziz

[Aziz]

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!!

Hi Ron,

there are multi-axis coil configurations too. But I wouldn't use them.
Cheers,
Aziz