THE ELUSVE 1us TC TARGET

[Tinkerer]

I was not aware that AMX was focussed on gold nuggets ... I thought the aim is to investigate and develop the idea of bipolar constant current pulse induction ( AKA CCPI ) and investigation of metal discrimination sensitivity etc. My own personal opinion is that the search for very small gold nuggets or jewellery ( eg 1us or less ) is already well covered and has been for at least the past 10 years at least by commercial detectors and some hobby detectors.
It is fairly easy to find the very small 1us targets even with sine wave based detectors operating at high frequencies ( eg 70 Khz ).

High power and Transmit Trickery dont really find the small nuggets ... its the RX processing ( whether the TX is pulse or sine ) the signal processing in the RX can detect these small targets if the processing is done right. Its arguable that high power detectors ( I would say the AMX is high power ) make it harder to detect small targets.

The real focus should be on dynamic range ( small to large targets ) and depth. If you make a deeper penetrating detector that can seek smaller targets deeper... then you are searching "new ground". If the previous detectors are not able to reach or detect a target at a certain depth then even if you search flogged areas that have been well searched before then its like searching an area that has not been searched before because your detector can see targets that other detectors cannot.

In summary the focus should be on depth and discrimination.

You bring up some good points.
The AMX should be a very simple, easy to use gold nugget detector, designed for the professional gold nugget prospector and artesanal gold digger. The target groups are the 1 to 2 million artesanal gold diggers in Africa and South America, who make a living digging for gold.
The machine should be extremely rugged, able to detect small and large gold nuggets in mineralised soil where the "Goldbug" and such VLF based detectrs do not work.

A good Ground Balance is a must.

I consider that the smallest gold nugget of interest would be of a TC of 1us.
Does the AMX need to be high power? maybe not for small nuggets. Rather high repetition rate like 10k to 20k PPs.
For deep larger nuggets, high power and lower PPs will be more effective. Maybe 1k to 5k PPs.
So we could consider a small shallow mode, maybe using an 8" coil and a deep high power mode for using a 12 to 14" coil.

And of course, the ideal would be a combination of short pulse cycles and long pulse cycles, like a CHIRP mode.

So you can see that there is a lot of research and development that can be done on this project. It would be worth it, as the target groups are growing exponentially with the raising gold prices.

In recent times we hear a lot of chatter about reverting to a gold standard to stabilize world currencies. If this happens, the gold prices will go through the roof.

[moodz]

The AMX project is specifically for gold nugget prospecting. A gold prospector searches for the existance of gold. There is much more smmall god than large gold. When he finds small gold, he usually knows in which direction he needs to search for the larger gold. Once the prospector locates a proper gold field, he can sell his claim to a gold mining company.
I know of a region where there exist gold fields totalling over thousand tons of gold. In ounces of gold, that is in the region of 50,000,000 ounces of gold.
Searching on a beach for lost gold jewelry, often the many gold chains escape the search, because on a gold chain the links are small and have a very short TC. The clasp is often the only part that can be detected. On beach gold, gold chains represent a significant amount of the total lost gold.
I know of beach gold detectorists who find more than one kilo of beach gold per year.

I was not aware that AMX was focussed on gold nuggets ... I thought the aim is to investigate and develop the idea of bipolar constant current pulse induction ( AKA CCPI ) and investigation of metal discrimination sensitivity etc. My own personal opinion is that the search for very small gold nuggets or jewellery ( eg 1us or less ) is already well covered and has been for at least the past 10 years at least by commercial detectors and some hobby detectors.
It is fairly easy to find the very small 1us targets even with sine wave based detectors operating at high frequencies ( eg 70 Khz ).

High power and Transmit Trickery dont really find the small nuggets ... its the RX processing ( whether the TX is pulse or sine ) the signal processing in the RX can detect these small targets if the processing is done right. Its arguable that high power detectors ( I would say the AMX is high power ) make it harder to detect small targets.

The real focus should be on dynamic range ( small to large targets ) and depth. If you make a deeper penetrating detector that can seek smaller targets deeper... then you are searching "new ground". If the previous detectors are not able to reach or detect a target at a certain depth then even if you search flogged areas that have been well searched before then its like searching an area that has not been searched before because your detector can see targets that other detectors cannot.

In summary the focus should be on depth and discrimination.

[Carl-NC]

... in practice, most of the searchers search for targets bigger to 1gram

In many cases, prospectors are chasing ever-smaller pieces of gold. I've witnessed the SDC-2300 hit a 1/2-grain (grain, not gram) nugget. At $2000/ounce that 1/2 grainer is worth $2, assuming 24k purity. People often chase targets worth far less.

[Detectorist#1]

OK Tinkerer. But I think that searching of the gold on the beaches is the work based of the unhappiness of the peoples. For that that small parts are indicators for near bigger parts - I have not observations.

[Tinkerer]

The AMX project is specifically for gold nugget prospecting. A gold prospector searches for the existance of gold. There is much more smmall god than large gold. When he finds small gold, he usually knows in which direction he needs to search for the larger gold. Once the prospector locates a proper gold field, he can sell his claim to a gold mining company.
I know of a region where there exist gold fields totalling over thousand tons of gold. In ounces of gold, that is in the region of 50,000,000 ounces of gold.
Searching on a beach for lost gold jewelry, often the many gold chains escape the search, because on a gold chain the links are small and have a very short TC. The clasp is often the only part that can be detected. On beach gold, gold chains represent a significant amount of the total lost gold.
I know of beach gold detectorists who find more than one kilo of beach gold per year.

[Detectorist#1]

Hi All,
This discussion for 1us target recognition is very interesting for theoretically and maybe practically conversation but as Ivconic said - in practice, most of the searchers search for targets bigger to 1gram - in opposite case our time is more expensive than finds! Correct me if I'm not right!

[Carl-NC]

I have been told that a 10 mm x 10 mm square of cheap ( thin not heavy duty ) kitchen foil is 0.7 microseconds. Might be .016 mils thick .... what is your opinion Carl ?

Sounds reasonable. I have that in my target set but have never measured the tau.

[moodz]

Any metal -- aluminum, copper, silver, lead -- can be used to create just about any tau you like. You only need to get the right dimensions. With extremely thin metal (aluminum foil or PCB copper foil) low taus are really easy, high taus become harder due to the thin metal. I stack aluminum foil in thickness for higher taus. Otherwise, you have to make the target bigger & bigger to achieve a higher tau and it's a diminishing return.

I have been told that a 10 mm x 10 mm square of cheap ( thin not heavy duty ) kitchen foil is 0.7 microseconds. Might be .016 mils thick .... what is your opinion Carl ?

[Altra]

Any metal -- aluminum, copper, silver, lead -- can be used to create just about any tau you like. You only need to get the right dimensions. With extremely thin metal (aluminum foil or PCB copper foil) low taus are really easy, high taus become harder due to the thin metal. I stack aluminum foil in thickness for higher taus. Otherwise, you have to make the target bigger & bigger to achieve a higher tau and it's a diminishing return.

That's good to know. The longer taus are not a problem since we have standard coins to use.

[Carl-NC]

Any metal -- aluminum, copper, silver, lead -- can be used to create just about any tau you like. You only need to get the right dimensions. With extremely thin metal (aluminum foil or PCB copper foil) low taus are really easy, high taus become harder due to the thin metal. I stack aluminum foil in thickness for higher taus. Otherwise, you have to make the target bigger & bigger to achieve a higher tau and it's a diminishing return.

[Altra]

After looking a little closer JLC offers an aluminum substrate with a copper surface. So the aluminum does not get etched only the copper. These boards are meant for heat dissipation.So this idea of using aluminum pcbs is out.

@Detectorist, copper is not a good test replacement for gold, but copper could be used as a sensitivity gauge by different sizes. For conductivity you can make a few turns of fine magnet wire about 30mm dia. and connect in series a low value resistor. TC = L/R

[Detectorist#1]

Hi Altra,
I admire your idea for easy preparing of standard targets! This is chart of conductivity order of the metals

The aluminium and the copper are closest to the gold but maybe PCBs from copper will be more cheap.

[Altra]

I been using the 5mm and 10mm squares cut from a aluminum beer can. But aluminum thickness and grade will vary from can to can. I had an idea for standardize targets. We could make them using a pcb. Draw up board with multiple geometries and sizes. These could then be cut into separate targets and glued to wands. This would create a standard gerber file that everyone could use. Assuming say 1 oz. copper, people around the world could test and compare results

I forgot to mention that most of the pcb makers offer aluminum now. This may be a better choice over copper for pi work. Not sure on the pricing? I would probably order a set of each.

[moodz]

Hi Moodz,
Don't be so angry! I understand well the idea of use external diode with lower VD for higher efficiency. All this is true when peek voltage is 1200V and the switching current is 1A.
The Sic transistor NTBG160N120SC1 (1200V 160mR) have VD of internal diode 3V at 1A current.
The SiC schottky diode IDM05G120C5 (1200V 5A) have VD 1.05V at 1A current. This is good primer for improved efficiency.
Go ahead in improving of AMX project!

OK ... we can move on to the next argument now

[Detectorist#1]

Hi Moodz,
Don't be so angry! I understand well the idea of use external diode with lower VD for higher efficiency. All this is true when peek voltage is 1200V and the switching current is 1A.
The Sic transistor NTBG160N120SC1 (1200V 160mR) have VD of internal diode 3V at 1A current.
The SiC schottky diode IDM05G120C5 (1200V 5A) have VD 1.05V at 1A current. This is good primer for improved efficiency.
Go ahead in improving of AMX project!