PI for larger objects at greater depth....

[Jim in Idaho]

I'm working an area that has fist-sized non-ferrous nodules. Is there a PI circuit design that would maximize the depth I could detect these? I don't care about small target sensitivity. Would a large, (maybe 24 x 24) coil, with my modified TDI SL work for this?
Many thanks,
Jim

[Carl-NC]

Do you know whether they give a fast or slow response? Generally with larger slow targets, a wider TX pulse width and wide sampling pulse, plus a large coil, will help a lot.

[eclipse]

The TDI SL won't work. At least alot of modifications needed.
Integrator TC: you need to adjust integrators;
Sample pulse widths: You need wider sample pulses (50-60) - with the MCU there it's a bit HARD
Frequency: You need to adjust the frequency to a lower (500-600 is the MAX) - with the MCU there it's a bit HARD
TX pulse width: you need at least 200us-300uS TX - with the MCU there it's a bit HARD
You need to remove the SAT resistors from both channels, and maybe the 5.6M resistor

As you can see alot of obstacles.

[Jim in Idaho]

Many thanks guys! Carl, this gives what I would call a slow response. It acts like a hot rock in some respects. Good hot signal that goes away fairly quickly as the coil is raised. It has a high resistance...in the neighborhood of 1.2megs/inch, but is a metal. It's got a high percentage of copper in it. I'm waiting on assay results now.
So, is there a PI I could use as a base for mods? Something cheap, maybe....LOL
I took the TM808 down there, and it can only see a 2lb hunk of this when the coil is almost on top of it. Goldmaster sees it fine, but can , with the 10" coil, only detect a 2oz piece at 10". At 12" can't see it at all. Pretty much the same for the TDI SL.
Jim

[nonkapo]

Sounds good field for Delta pulse isn't it? I guess the Baracuda with big enough coil may do too.

[Jim in Idaho]

I found a DP on EBay, and bought it. Not certain of what I bought, but the price was affordable.
Jim

https://www.ebay.com/itm/Deep-Metal-detector-DELTA-PULSE/164281796304?ssPageName=STRK%3AMEBIDX%3AIT&_trksid =p2057872.m2749.l2649

[surfdetector]

Hi Jim,
KT315 is currently selling a batch of Delta Pulse PCBs, you might want to contact him.
Cheers

[Jim in Idaho]

Hi Jim,
KT315 is currently selling a batch of Delta Pulse PCBs, you might want to contact him.
Cheers

Yes, but I already bought one. It came today. I played with it tonight, getting use to the controls. With the 1 meter coil it detects my 1 kilo copper nugget at about 18". Almost exactly the same as the GM24K with the 8 x 14 coil. I think I need a smaller coil for the Delta P. I'm going to make a 2' square to start. See how that does, and go from there.
Jim

[Jim in Idaho]

I need some more help, guys. I'm trying to detect non-ferrous material golfball-sized and larger, at depth...maybe 24" deep. This material, is a high-conductor. It gives a low tone on my TDI SL. I'm going to make my own coils for the Delta Pulse. All things being equal, do I want a high inductance around 1,000uH, or low...350-500uH, to optimize my detecting. I'm thinking of a 20-24" coil. The 1 meter coil that came with the Delta is 600uH. It detects a 1 kilo hunk of this material at 17" in air. I'd like to do better.
I appreciate any help.
Jim

[Vadim18]

I need some more help, guys. I'm trying to detect non-ferrous material golfball-sized and larger, at depth...maybe 24" deep. This material, is a high-conductor. It gives a low tone on my TDI SL. I'm going to make my own coils for the Delta Pulse. All things being equal, do I want a high inductance around 1,000uH, or low...350-500uH, to optimize my detecting. I'm thinking of a 20-24" coil. The 1 meter coil that came with the Delta is 600uH. It detects a 1 kilo hunk of this material at 17" in air. I'd like to do better.
I appreciate any help.
Jim

Quite deep target fo such size. You can try to made flat coil 450-500 uH + 2 ohm resistor in series. Than Increase pulse width until power supply curent reach 120 mA. With these settings i detect 1 grivna coin up to 45 cm, yes, in the air offcourse. My coil are 27 cm in diameter. I can make foto of my coil, but little bit later.

[Vadim18]

Here is my coil foto. Inner diameter -24 cm, outher - 27,5 cm, number of turns ~27. I use 0.55 mm wire, but 0.4 - 0.5 mm will suit better.
(Inductance 473 uH, resistance 2 Ohm, coil only SFR 0,725 kHz, damping resistance 890 Ohm)
With this coil coin detecatble at 45 cm in the air, so i think with 17" coil you can detect your target easy.

[Jim in Idaho]

That is a really nice build, Vlad. Thanks you.
Jim

[kt315]

cache test of Carl. if you did not still read. https://www.geotech1.com/forums/show...831-Cache-Test

[Jim in Idaho]

That's an informative read, KT...thanks!
Jim