Metal detector experiments.

[M.D. prototypes]

Highly mineralized piece of brick.

[Darin]

What kind of detector are you using in you video.

[baum7154]

The golden ring has a weight of about 3 grains and is a closed loop. It would be interesting to know the detection distance of the ring presented 'edge on ' to the coil. It would also be interesting to know the detection distance of the same weight of gold that is not in the form of a closed ring. The closed ring geometry creates much stronger eddy currents than a lump of the same material and weight. Is it possible for you to run these tests?

Regards,

Dan

[M.D. prototypes]

@ Darin
VLF



@ baum7154
You're absolutely right. The closed ring creates much stronger eddy currents.
If objects have another form than a ring or you present them with another angle in front of the coil then eddy currents are smaller.
This also depends on the type of material of the object, and probably more factors that have an influence on it.
At this moment can't record videos but it's a good idea to compare it.

[bernte_one]

hello mr. md prototypes

are you sure you haven´t already a account here under another name?

performance of detector look great

[M.D. prototypes]

hello mr. md prototypes

are you sure you haven´t already a account here under another name?

performance of detector look great

Yes, I'm sure.
Thank you for the positive comment on the detector.

[M.D. prototypes]

Overload Experiment

[6666]

Thats impressive, but now suspend the ring in the pile of metal and swing the detector.

[M.D. prototypes]

Thats impressive, but now suspend the ring in the pile of metal and swing the detector.

Thanks for your comment.

If we place the ring between the iron and we swing with this detector over it (as in your example) then you will hear a low tone (for iron) through the large iron masses. He will not become unstable and he will not give an overload alarm (a "fire" alarm so that nothing more can be detected) or give no signal as some detectors do.
You can see an example of it in this video:http://www.youtube.com/watch?v=KKoMyIGR9UM. With a few nails, the detectors has already overload problems.

In our experiment, it was not about the discrimination of the ring and the silver coin but whether the detector would detect with a high tone or would be unstable. Due to the large presence of a large amount of iron, the electromagnetic field is disturbed in such a way that some detectors are no longer able to detect and / or become unstable, or they will give a wrong tone by the detection.
In our video, at 00:12, you can hear a short low tone which is not the intention, but otherwise the detector does it pretty good. From minute 1:10, the iron objects are moved, but the detector continues to work well, he still discriminates good and he gives no signs of instability or overload.

[CAS]

The machine (what we have seen of it) appears to work quite impressively. I am just wondering what the purpose of showing us these videos are? Are you going to share the circuit, design specs etc? Or is this just a promotional 'show and tell' in order to generate interest in a commercial machine?

Sorry if I sound a little suspicious but you have been a little vague on the machine itself. This being a tech forum and all, I am sure most of us here would be really interested in the details of the detector ie schematics etc.

[Koala]

Thats impressive, but now suspend the ring in the pile of metal and swing the detector.

just tried my IDX that overloads in the field all the time with plow shear. Put loads of iron in front of the coil swing a small silver coin or gold ring in front of the coil works fine.


Same with the first video tried with granite and brick and coke that's pick up in all metal mode. Switch to disc mode nothing add coin or ring see them just fine.

[Qiaozhi]

just tried my IDX that overloads in the field all the time with plow shear. Put loads of iron in front of the coil swing a small silver coin or gold ring in front of the coil works fine.


Same with the first video tried with granite and brick and coke that's pick up in all metal mode. Switch to disc mode nothing add coin or ring see them just fine.

This is because the detector reacts to the rate-of-change of the received signal, and not the amplitude of the signal itself. Since the coin is moving relative to the coil, and the other metal is stationary, it will still be able to detect the coin. If the coin is placed in the middle of the iron junk, and the coil was in motion, the overwhelming amount of ferrous compared to non-ferrous objects will mask the coin completely, which is a more practical test than the one in the video. Even if you consider the test to be demonstrating the detection of a coin in extremely severe ground conditions, the reality is that it would be highly unlikely that the ground would be homogeneous, and ground balancing with a VLF detector would be impossible.

However, placing a huge amount of iron in front of the coil will upset the inductance balance, and could cause the preamp to rail out. I suspect if you were to place the coil on top of a metal drain cover, you wouldn't be able to detect the moving coin.

[M.D. prototypes]

The machine (what we have seen of it) appears to work quite impressively. I am just wondering what the purpose of showing us these videos are? Are you going to share the circuit, design specs etc? Or is this just a promotional 'show and tell' in order to generate interest in a commercial machine?

Sorry if I sound a little suspicious but you have been a little vague on the machine itself. This being a tech forum and all, I am sure most of us here would be really interested in the details of the detector ie schematics etc.

Thanks for your two cents.

The purpose of these video's are to try out the behavior and the extremes of VLF/IB detectors and prototypes. The whole idea of this is to share experiences and video's and/or to discuss about it, with anyone who's is interested in it.

If you would like some technical information, here are some details: VLF/IB detector, double D elliptical coil of 18.5 x 14cm - 7.2 "x 5.5 ", operating frequency 14.3 KHz, 21 p.p. Volt oscillator power, 7.1 Volt working voltage, battery voltage 12 Volt.

Now, if we want to show a schematic or want to start a project we will place it on: Tech forum/schematics/projects.

[eduardo1979]

The sound of the detector is very similar to the Deeptech (Vista Gold, Smart, etc)...

[M.D. prototypes]

The sound of the detector is very similar to the Deeptech (Vista Gold, Smart, etc)...

It sounds like it, it's a nice sound.