Technology Forum

I keep hearing that a PI will detect deeper in the ground than in an air test, if this is true, how is it possible?

In general terms, No. The range will be greatest without the interference of the ground matrix. With this said, there are thoughts, (me too), that in a salt environment the target could/may be enhanced a tad by the influence of the salt.

This is very hard to back up. One can test this by taking a low conductive target like a US Nickel, (don't use other coins), air test it to the max, and then bury it in the damp salt, sand same as your air test. If the salt enhances it, you should hear it. Although this doesn't take into account of testing in disturbed ground, PI's don't seem to be affected by this as much as a VLF detector is, and certainly not on the salt.

Most PI units perform better on low conductive items. Gold jewelry is such a item, so is the nickel. Keep this in mind when doing random air test with VLF units. The PI's claim to fame is that it can handle bad ground matrix far better than VLF detectors can. Salt, although it's a positive target, unlike most bad ground, VLF detectors don't like being around it very well. This is where the PI does it's best.

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Mr. Bill

I have had people tell me that they have dug gold nuggets at certain depths, then reburied the same nugget at the same depth in the same hole and not be able to detect it. If this is true it must have something to do with the disturbed soil matrix, maybe the FE3O4 in the soil. Yes, I know sometimes the nugget was not as deep as the digger thought it was, but I have heard this lot of times, (mostly Minelab owners) by experienced hunters.

It can't in a 'non-contributory' matrix.

BUT as Bill suggested (correctly), any conductive surroundings may initiate the same enhancement as does the conductive 'halo' provided by the migration of metal from the target, into the surrounding soil, and so enlarging the 'electrical image. This is due to electrolytic action with sulphides /salts in contact with the target....especially silver.

Any such indication, when immediately testing that target placed in the ground, ( if at all possible), is due to some unidentified circumstances not associated with the functionality of the detector.

Dropping into salty water is a possible way to 'extend' its detectability. My E-Trac has several deep, thick, silver finds to its credit from wet salt beaches, much deeper than any found on land.
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TheMarshall



Edited 2 time(s). Last edit at 01/26/2012 10:49AM by TheMarshall.

There is a difference between burying a coin and a coin that has been in the ground for a while, i don't know what makes it different but once the dirt is disturbed its never the same as far as depth.

I have dug quarters at 12" in wet sand and 8" is as deep as it would detect bench testing. This is with a Sand Shark.

I use the Dual Field and have used a Sand Shark. Air testing does not show depth. It's only real use is to help learn sounds. When a target sits in the ground it causes what some call a halo. The sand is not disturbed around it and the pulse recognises the target easy. Also, my understanding is the sand is conductive with salt minerals which help the machine go deeper by pulling the pulse deeper. All I can say is air tests give me little depth. I dig targets on a regular basis over a foot deep.

To me, It seems like my pulses go 50% deeper in the wet sand than an air test, at least it feels that way when I am digging them. I'm sure this can not be true, but it seems that way. It is more likely it is around a 20% gain on most beaches. Now in dirt ground (and my local ground is pretty mineralized), it seems to cut the depth in 1/2, again probably an exaggeration.

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imalookin2
I use the Dual Field and have used a Sand Shark. Air testing does not show depth. It's only real use is to help learn sounds. When a target sits in the ground it causes what some call a halo. The sand is not disturbed around it and the pulse recognises the target easy. Also, my understanding is the sand is conductive with salt minerals which help the machine go deeper by pulling the pulse deeper. All I can say is air tests give me little depth. I dig targets on a regular basis over a foot deep.

imalookin2
Just to answer,
Which one do you think is better PI Unit? (Dual Field or Sand Shark)
I'll be buy one PI unit and doing some research.
Thank's for the input.

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imalookin2
I use the Dual Field and have used a Sand Shark. Air testing does not show depth. It's only real use is to help learn sounds. When a target sits in the ground it causes what some call a halo. The sand is not disturbed around it and the pulse recognises the target easy. Also, my understanding is the sand is conductive with salt minerals which help the machine go deeper by pulling the pulse deeper. All I can say is air tests give me little depth. I dig targets on a regular basis over a foot deep.

I agree with most of the experts and don't beleive in the "Halo effect" on non-ferrous metals.

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adolfo.martinez

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imalookin2
I use the Dual Field and have used a Sand Shark. Air testing does not show depth. It's only real use is to help learn sounds. When a target sits in the ground it causes what some call a halo. The sand is not disturbed around it and the pulse recognises the target easy. Also, my understanding is the sand is conductive with salt minerals which help the machine go deeper by pulling the pulse deeper. All I can say is air tests give me little depth. I dig targets on a regular basis over a foot deep.

imalookin2
Just to answer,
Which one do you think is better PI Unit? (Dual Field or Sand Shark)
I'll be buy one PI unit and doing some research.
Thank's for the input.

I don't own a Dual Field, but have owned a Sand Shark, and sold it to buy the Infinium. The Infinium blows the Sand Shark away depth wise, and in sensitivity to small gold. I hear the Dual Field is close to the depth of the Infinium.

Hello, I have read some post from Eric Foster, which says the PI detectors, they see a "halo effect".

Excuse my bad English. use online translator.

Greetings.


Hola, creo haber leido algun post de Eric Foster, en el que dice que los detectores de PI, no ven el efecto "halo".

Perdonad mi mal ingles. uso traductor online.

Saludos.

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Used: Tesoro Euro Sabre, Minelab Excalibur, Goldscan 5.

Last week a friend had a small nugget which my Infinium wouldn't detect in an air test until only 1 inch away. We buried it at
3 inches and got a good signal, no ifs ands or buts. Yes, it will detect deeper in the ground than in the air
It reminds me of the old Compass Depth Doubler, where you charge up the ground and any detector will detect almost twice
as deep. Maybe that is what PI units are doing, charging up the ground..
Rich

I can never see why more people just don't go out and do the tests re halos.

Consider that much land and most beaches don't allow any "halo" to develop as the metal item is being moved by its weight, worm action, frost action, ploughing and on the beach wind and tide action. Then ask if you really, really want extra depth thats down to halo effect because to have the effect you need a chemical/electrical reaction which is destroying the item involved.

VLF's respond really well (or should I say badly unless your after old iron) to ferrous halo's but this isn't the case with P.I.'s. I'm pretty certain Eric Foster made a post on this subject some years back saying that pulse machines didn't respond to halo effect as the rusted iron oxide has insufficient metal content left and that hydrated iron oxide does not give a magnetic signal.

This doesn't mean that a pulse design can't benefit to some degree from wet salt but what is certain is that as Mr.Bill says at the bottom of the page, VLF's suffer badly in the salt so thats a big plus to the use of a pulse design. What always has to be considered in air v ground tests with any detector design is that people can't estimate depth and the worse at pinpointing they are the more the possibility that they dig past a target which then falls down as they continue to dig into the now deep hole leading to the reports of finds at exceptional depth.