Question for Eric Foster

[Eddie K.]

First of all Hi, and I am new to this form and the use of P.I. technology.

Eric,

I just purchased one of your Goldscan 5 machines. I've always been interested in P.I. machines, but have been reluctant in purchasing one because of not being able to discriminate between ferrous and non-ferrous.

I live in the Baton Rouge, Louisiana area, and I mostly hunt for pre civil war and civil war artifacts. I purchased your goldscan 5 in hopes it will be able to detect deeper targets than those that most VLF detectors have detected and the fact that you have a developed a ferrous non-ferrous I. D.ing circuit. I have a civil war battlefield area that has produced numerous relics, but has small and large iron mixed with some modern trash along with desirable targets. It has three major high power lines running through the area. The other area has very little modern trash, but was heavily shelled and confederates where dug in rat holes in the banks.

I was able to eliminate almost all of the electrical interference by lowering my pulse width from 25 micro seconds to around 12.5. The problem I am having is being able to tell the difference between the ferrous and non-ferrous. We have had a lot of rain in this part of the country over the last two weeks and the rusted iron is leaching into the soil really bad creating a halo around these targets. Most VLF detectors will false on these types of targets in this type of condition. Is there a way that it might be possible to tell a slight difference in the Low-High sounds (Woo Wee)? I'm using Black Widow Headphones with this unit. Maybe I need to try a different type or brand to help with the tones? I'm using the 11" mono coil. This was Bills personal unit. Thanks!

Eddie

 

[desertdon]

try this with DD coil. Raise coil above target and go straight down on it, if it is iron it should null out. Also, iron usually has double blip to signal as coil goes across with both sides. Don

 

[Eric Foster]

Hi Eddie,

The iron ID on the GS5 is a spin off from the method used for ground balance. Iron targets have a mixed decay consisting of a conductivity response, superimposed on a magnetic relaxation response. Which dominates depends very much on the size and shape of the iron target. For examplpe a thin nail or piece of ferrous wire will have little conductive response, but a strong magnetic one. The flux lines from the coil have to be along the nail for the strongest magnetic response. That is why a horizontal nail will ge a double blip, as it passes under the edge of the coil, with little or no response in the middle. Flat thin iron gives both responses, as under the centre of the coil, the conductive response can be very strong. Iron often goes WOO - WEE - WOO when you scan across in one direction, and often with a different response when scanned at right angles. Some practice is required to attune the ear to the different responses, but you can become quite proficient at iron ID, and many users have.

I'm not clear what you mean by lowering the pulse width from 25 to 12.5uS. What control are you using? PI detectors do not respond to "halo" effects. Rusted iron oxide will give no signal, as there is no metal content left, and hydrated iron oxide does not give a magnetic signal.

Eric.

 

[bakergeol]

Hi Eddie
Most of the following I already had forwarded to you in an email. But I am curious to what others have found.


What tricks have you folks discovered? The following writeup is what I assume all GS5 owners know? If you have a different technique- I am all ears.

I remembered when I first obtained the GS5 I used a elliptical coil and tried toe versus center of the coil usage similar to the Infinium and various pulse delay and GB settings. I made lists of the results and yes you can go quite far in IDing different metals. However, it just wasn't practical as one would be forever expanding the list and it requires quite a memory too. In addition applying different settings would be time consuming. Still bury all the copper pennies and silver dimes you want and I can tell you which is which. I abandoned the project for another reason too. Lets be honest the GS5 was designed for low conductors- really hot on gold here. For coin machines there are a lot of VLFs out there which will do a better job on coins than the GS5.

OK what would be the best settings for relic hunting? First off I use a DD coil and like to run it in PI mode which is the most sensitive. I use the GB mode for metal ID. I don't hunt in highly mineralized areas. Having the GB mode at the 3:00 position one can distinguish iron by the low tone or the double blip. Small low conductors such as small lead,small AL and small gold will of course produce a high tone. Not all iron produces a double blip. Unfortunately a lot of good items such as mini balls, large and small buttons, copper, silver also produce a low tone here too.

Would not the correct inital relic hunting setting for metal ID be at the 10:00 position? This is your basic ferrous/non ferrous setting. Low tones here would mean non ferrous.(Probably the only PI currently in production that can distinuish a large gold nugget from any iron of any size) Larger low conductors such as mini balls, large brass buttons,as well as high conductors such as copper or silver would produce low tones. Iron and steel does not produce a low tone here just a high tone. Small low conductors such as small buttons, small lead will also produce a high tone. Moving the GB to near the 1 o'clock position and your small brass buttons will still produce a high tone whereas most iron will have a low tone or double blip. At the 3:00 position your small brass buttons will have a low tone and only small lead and gold will produce a high tone.

Learning signal intensity at the 10:00 position is important. You have to remember that the GS5 is geared toward small gold. This is good actually. I practice with different size objects here. The point is that a large iron object will produce an unusually large signal response at the 10:00 position. These are the type of signals that will produce a double blip response beyond the 12:00 position. Small low conductors which can only produce a high tone here do not have this large response.

So would not the correct sequence for relic hunting ID be the 1. 10:00(ferrous/non ferrous) 2. 1:00(distinuish small brass from iron) and then 3. 3:00 position or beyond 1:00(small lead,gold from iron)? Recent bottlecaps you are stuck with.

Regarding heat treated metal which produces a high tone at the 3:00 position. Anyone found a trick for recent bottle caps? Larger heat treated items which produce a high tone can of course be recognized by their large signal response. Again recognize how small low conductors respond with their high tone.

Again I assume all GS5 users know the above. Comments from anyone using the GS5 for relic hunting?

George

 

[Mr.Bill]

n/t

 

[MahatMacoat]

I have also found when hunting in straight Pi mode you can even eliminate sounds from certain targets by moving the ground balance control. You can not do this when your forced to hunt in the ground balance mode because of mineralized ground. The position of the dial will be determined by the amount of ground mineral. When hunting on our salt water beach I hunted in the straight PI mode and noticed if I set the ground balance knob towards minus I got rid of most coins and eliminated the low tone. Just dug high tones with bobbie pins giving you the double tone. This machine has great potential as we discover more thru experimentation.

 

[MahatMacoat]

n/t

 

[desertdon]

P.S. you hae to be in a ground balance mode to do this. Don

 

[Eddie K.]

Thanks!

 

[Eddie K.]

I had set the pulse delay at 25 micro seconds at first, but there are three high voltage power lines running through this area I'm hunting that gave me trouble even with the Tx switch fully clockwise. After turning back on the pulse delay to about the 12 o'clock position, I was able to get the unit to stabilize.

 

[Eric Foster]

It is usually the TX FREQ that is adjusted to counteract interference, rather than P.DELAY. The latter sets the small object response where 10uS is the highest sensitivity. Shifting the P.Delay may help with interference, but that is not its primary function.

Eric.

 

[Eddie K.]

Correct. I didn't quite understand why this would have had an effect with the interference either.

 

[desertdon]

You use P.Delay to help balance aftermarket coil, especially if larger, TX Freg will help with electrical interfence as Eric said, two different things. Good Luck....Don