Eric Foster quote on how to "air test" PI detectors and his warning about applying the same test to induction balanced detectors.

[Crumble]

I had always heard the same about the signal traveling deeper in the water than in the air. I also heard that there is hardly any halo effect if there is any at all for gold which is what 95% of us water hunters are looking for. I have found gold rings on the beach with my Excal in discriminate as deep as some of those air tests. So I think for the most part the air tests are a waste of time. Just my 2¢ like it or not.

PIs definitely get more depth in the ground, than they show in air tests. I think the magnetic field created by the coil pushed into very conductive ground charges the target more, and as long as the ground returns to zero before the sampling (pulse delay), the target will hold a charge longer than it would in an air test, because it got that extra charge, thus giving a signal when it wouldn't without that extra charge.

The thing is, this is linear across all PIs, if the Sand Shark gains 2 inches of depth in the ground, so will the Dual Field, and the Headhunter, etc. So the air test results still hold true in the ground when comparing two machines, if one machine gets much less depth in an air test, it will still get less depth in the ground. While air tests don't show the true max depth of the machine, they are good for comparing the depth of different machines, and the difference in depth between different size/conductivity targets.

 

[Terry Soloman]

.

 

[Rudy]

I think the magnetic field created by the coil pushed into very conductive ground charges the target more, and as long as the ground returns to zero before the sampling (pulse delay), the target will hold a charge longer than it would in an air test, because it got that extra charge, thus giving a signal when it wouldn't without that extra charge.

Sounds like voodoo physics.

 

[Crumble]

Sounds like voodoo physics.

Yeah, lol, maybe the conductive ground just allows the field from the coil to reach deeper, or keeps the fields condensed for a greater depth, or something. So many people can see the greater depth on salty sand with PIs, but nobody had been able explain it...

 

[Raphis]

The point I wish to state is that the halo effect is present even in saltwater.

Showing a corroded ring dug from the beach has nothing to do with the meaning of "halo effect". A corroded ring just means the salt is starting to decompose the metal, but it doesn't mean a halo was around that target when you dug it. For the halo effect to be a "halo effect", that target has to remain in the same position for an undetermined length of time, creating an area in the surrounding dirt/clay/sand/etc. of decomposition all around the metallic target. The area in the ground around this stationary target is called the "halo" area. It's very possible your ring had been stationary and was corroding for a length of time in the sand before you found it. There would have been a halo of decomposition around that ring....but, if you were to re-bury that ring, for instance, there would be no halo, just a corroded ring, until ample time has passed and further decomposition of the stationary target takes place. I have found many corroded/oxidized silver/copper coins in gopher mounds at old parks. Just because the coin is corroded doesn't mean there was a halo around it when I dug it.....it only means there probably was one around it before the gopher brought it up to the surface, but not anymore. Similarly, finding old, corroded coins or pieces of decomposed metal near the surface of the wet sand after recent heavy erosion means no halo is present around those objects when you dug them, but more than likely, there probably was a halo present before the beach erosion took place.

Halo effect is definitely real in the ground and at the beach, but only with stationary or semi-stationary targets. The ground/strata above/below/around the target needs to be undisturbed for a length of time during decomposition of the object. There's a term that I've seen many hunters use...they say they "broke the halo" when digging up a target.....happens all the time while recovering targets.

 

[Crumble]

Raphis just reminded me of something, I know it happens to all of us PI hunters constantly. When you get a deep signal, dig a few scoops and it disappears, then the next scoop you have it. I think it's less the halo being broken, and more, the PI not being able to reach that deep with just airspace between the coil and target. A lot of times it will happen and the target will still be a few more inches down, and still has its halo. I think the halo helped you hear it in the first place, but the airspace is what makes it disappear, not the halo being broken.