Can pinpointer detecting thin chain?

[Polymer]

It's the definition of all induction-based metal detectors. Target eddy currents induce an EMF in the RX coil; for IB/VLF that's a dedicated RX coil, for PI it's the same coil as was used for TX 10us ago, and in proximity detectors (BFO, energy theft) it's the same coil as is continuously transmitting.

I re-read the math section, and I'm pretty sure there are major errors. Eq 6 does not look at all right, and Eq 7 & 8 are definitely not the derivatives of 6. If I get time I will try to grind through it and see what it should be.

Thank you again Carl!

If I have comprehended this right, basically all metal detectors are in the "near field" and inductively-coupled ...?
As compared to say a radar which is "far field" and "reflectively" evaluated.

I am sure there must be other methods too. I spoke with a R&D guy of ultrasound products about the possibilities of ultrasound to image the sea floor in salt water,
with a resolution in the low millimeter range (chains/rings) and a resonable depth as to recognise the shape of denser objects in the substrate, without all the issues that PI/VLF have in sea water.

The conversation went quite well and I was excited until the question was asked "what particulate size" ... Me: ???
"In the water". Oh my, theres always stuff swimming around and the relevant sizing was u-meter range if I recall properly.
So that was that. I could have gotten testing done for my specs ... would have cost around 6000 USD.
Since I just want easier detecting and not jumping into starting a new company, I left it at that.

Perhaps someone else is deeper into this.

I read an article about a type of GPR around 25-30 years ago. It was military and in the testing phase for "looking" into the ground for mines. Geometric recognition also.
It was interesting and apparently it worked. Drawbacks: it needed liquid nitrogen for cooling, cost a fortune and weighed a helluva lot.
I sort of tried following it up, but never found anything about it again.

Gosh, Ive digressed.

More questions on the NUPI pinpointer to come - I have a soft spot for this simple device.

[getsa]

Hello everyone,
Here is my result with Nupi ...
https://www.youtube.com/shorts/Tnj76--DixU
Greetings!

[MartyJ1963]

Hiya Getsa, I viewed your video,,,,Great result! Which schematic and pcb layout did you use and what are is your coil data please? Thanks, Regards, Marty.

[getsa]

The PCB is perfoboard. The schematic is the modified one (page 24). Turns are 208/69.
Greetings!

[MartyJ1963]

Thanks Getsa! Much appreciated! Regards, Marty.

[hadireyhani]

good job