Cache Test

[Tim Williams]

Carl sense this is a test for depth. What do you think about testing under wet verses dry conditions? Do you think it would be possible that a heavy rain may improve depth?

Just a thought and if one of your detectors would pick it up after the ground is saturated it may prove the best time for cache hunting.

Just a thought,

Tim

[Ferric Toes]

Hello Eric.

My new test site is in the back garden of Mike Longfield. He is a very old detector dealer in the UK. He lives near Birmingham.
You could get there if possible and test you detectors. The cashe is 1kg. of various bronze-copper-silver coins and very few modern iron based 2 pence coins all at 24" depth.
You can see pictures of that test site in www.nexusdetectors.com the Tests page.
If you do go there it will be interesting to see how the PI detectors will respond to that test.
Best regards.
Georgi, Nexus

Hi Georgi,

I know Mike very well and will make an appointment to visit in the next two or three months. Easy journey from Oxford.

Eric.

[Esteban]

The only "problem" isn't the poor electrical contact between the coins, the main problem is the area. If you weld all the 200 coins in a form of tower and put the end of this tower at the same distance (25 inches or 66 cm or 2 feet) you can't detect easily. Now, weld only 20 coins in plane form and put at same distance... this is another history because has plane area, "face".

I think the next generation of detector will be via ultrasonic ray for to measure density. Different density mean different absorption in ultrasonic, a kind of "ultrasonic" densimeter. So, if each material absorbs a quantity of ultrasonic ray, will be more easy the "classification" of materials, extended for no metal items.

[Delbert grady]

ultrasonic ray ???????

So ultrasonic is a sound wave about 40khz that won't go through dry soil.

And a ray is some sort of light.

I don't think so

[Unregistered]

Hi Georgi,

I know Mike very well and will make an appointment to visit in the next two or three months. Easy journey from Oxford.

Eric.

That is good to hear.
It will be good if we can get together to test some PI detectors.
The only test I have done on PI was bench test on Minelab GP3500 with 18" coil. It was not very inmpressive.
All best.
Georgi

[Esteban]

So what? Ultrasonic can penetrate. is a relative low frequency.

[Unregistered]

Bucket o' coins at the bottom of the hole. Like Gary, I also notched out a little side cubby to stick the coins in, so the soil immediately above the cache is undisturbed.

Hi Carl.
I got a bit of help for your cashe test.
If you get the cashe deeper under the compact soil that will improve your chances to detect it.
Most of the detectors would miss the cashe in your set up because the disturbed soil from the hole will create strong ground signal counteracting the signal from the cashe.
For this reason you should try to put the cashe some 8 - 10" deeper under the undisturbed soil and get some distanse from the edge of the hole.
However the detector should be able to pick up the cashe in air at min. of 30" distance to have some reasonable chance to find it at 24" under ground.
All best.
Georgi

[michael]

...If you get the cashe deeper under the compact soil that will improve your chances to detect it.
Most of the detectors would miss the cashe in your set up because the disturbed soil from the hole will create strong ground signal counteracting the signal from the cashe...

I thoroughly agree with this, cose I have experienced this. I think air test is not comparable to buried test especially old buried. One experienced guy 7 years ago told this to me.
he told. He believed compact soil acts as wire. when you disturb soil have cut it.maybe this is due to field formation around old buried objects that guy told in other way.

[Unregistered]

I thoroughly agree with this, cose I have experienced this. I think air test is not comparable to buried test especially old buried. One experienced guy 7 years ago told this to me.
he told. He believed compact soil acts as wire. when you disturb soil have cut it.maybe this is due to field formation around old buried objects that guy told in other way.

When the soil is disturbed it permability changes as well, as a result of lower conductivity.
Disturbed soil causes lower losses for the transmitted signals.
However a desturbed soil in contained area (hole) will increase the ground effect for all detectors, because it presents rapid change in the ground mineral conditions.
Targets on the bottom of hole are easier to detect than the ones under compact soil, but targets burried just under the edge of a hole under the compact soil are more dificult to detect than long time burried targets under compact soil.

[Ferric Toes]

When the soil is disturbed it permability changes as well, as a result of lower conductivity.
Disturbed soil causes lower losses for the transmitted signals.
However a desturbed soil in contained area (hole) will increase the ground effect for all detectors, because it presents rapid change in the ground mineral conditions.

PI detectors do not respond to changes in magnetic permiability, but what is often associated with a permiable soil is a magnetic lag, or viscosity. This quality does result in a signal, which if not balanced out, will give a negative response when going over a hole. A ground balancing PI, such as the Goldscan 5, will not respond to a hole even in very strongly iron mineralised ground. However, even a purely permiable material that gives no signal of itself, can distort the transmitted field from the coil so that less reaches the target. If I wanted to hide a cache and make it completely undetectable to a PI, I would put it in a ferrite pot.

Eric.

[Unregistered]

PI detectors do not respond to changes in magnetic permiability, but what is often associated with a permiable soil is a magnetic lag, or viscosity. This quality does result in a signal, which if not balanced out, will give a negative response when going over a hole. A ground balancing PI, such as the Goldscan 5, will not respond to a hole even in very strongly iron mineralised ground. However, even a purely permiable material that gives no signal of itself, can distort the transmitted field from the coil so that less reaches the target. If I wanted to hide a cache and make it completely undetectable to a PI, I would put it in a ferrite pot.

Eric.

Well I do not know much about PI detectors. I believe this note was related to the way induction balance detectors work (guess). All of them are badly afected by holes when deep search is consern.
It is strange that the PI`s Carl used for the cashe test did not detect the cashe, providing they do not respond to the hole as you say.
What is the reason that they can not get to the cashe then?

Georgi

[Unregistered]

JC1

What is the reason that they can not get to the cashe then?

(Carl is using the same set of worn out batteries in all
the detectors)

If I wanted to hide a cache and make it completely undetectable to a PI,

I would put it in a ferrite pot.

Now that's funny. And a Great Idea!!!

[Unregistered]

What is the reason that they can not get to the cashe then?

(Carl is using the same set of worn out batteries in all
the detectors)

If I wanted to hide a cache and make it completely undetectable to a PI,

I would put it in a ferrite pot.

Now that's funny. And a Great Idea!!!

You know what? It would be good idea if you get out and make some life for your self. Do something constructive or may be find a woman.
This is a place where people waht to share some ideas, not listening to this childish nonsence.

[Ferric Toes]

You know what? It would be good idea if you get out and make some life for your self. Do something constructive or may be find a woman.
This is a place where people waht to share some ideas, not listening to this childish nonsence.

What is wrong with the occasional humorous remark Mr Anonymous? JC1 is a very competent electronics engineer and has posted much very helpful and "in depth" information over a long period of time.

If you are also refering to my statement about a ferrite pot, that is not nonsense and was used to illustrate the shorting effect that a permiable material has on a magnetic field. I have used this technique in certain PI applications.

If what you read is childish nonsense, let us have some real technical gems. But first, give yourself a name.

Eric Foster.

[Unregistered]

What is wrong with the occasional humorous remark Mr Anonymous? JC1 is a very competent electronics engineer and has posted much very helpful and "in depth" information over a long period of time.

If you are also refering to my statement about a ferrite pot, that is not nonsense and was used to illustrate the shorting effect that a permiable material has on a magnetic field. I have used this technique in certain PI applications.

If what you read is childish nonsense, let us have some real technical gems. But first, give yourself a name.

Eric Foster.

Sorry but this was an answer to the JC1 "joke", not a comment to your statements.
It just did not appear to me that way.
It is difficult to tolerate jokes which makes other people appear stupid.

Now about the ferrite pot. The attempt to illustrate the shorting effect is good idea, but in this case a bit exessive I think, considering that the ground minerals are not any near as permiable as ferrite materials, unless you reffer to a ferrite pot with less permiability than a standard ferrite ring for example, used for coils and transformers.
However it is correct that the permiable materials (ground minerals) are the very reason for all detectors to suffer loss of sensitivity under ground, compared to an air test, as a result of the shorting effect.

I apologize about not giving my name. I have noticed that there are to many "bites" on the forums.