Inside the Metal Detector Appendix B Resources

[CrizzyD]

In the resources section at the back of the book, there is a big list of books and Magazine Articles. Perhaps it is my Google Fu failing me, but I'm finding it incredibly difficult to find a lot of what's listed. Is there a collation of these items somewhere in some database? Could anyone point me in the correct direction for the majority of these articles, or are they (as I suspect) scattered across the internet if even present anymore? I'm asking as I'm writing a scientific paper and the book has been a great springboard for a lot of the more technical ideas but there just isn't much in regards to publicly available scientific research. And patents are almost always useless. I'm asking for the magazine articles as they seem to be the most common (and its better than nothing). So I have two main questions. Q1 is there a big database of magazine articles and books that may contain a lot of what's listed in the book? Q2 is there anywhere online where I may have more luck finding technical papers/information regarding metal detection, specifically PI? Thanks!

[Carl-NC]

Many of the articles are posted in the root Geotech web site, https://www.geotech1.com. You can also find a lot of the magazines at https://worldradiohistory.com. I keep a personal list of articles, but most of them are in the appendix.

[CrizzyD]

Thanks, https://worldradiohistory.com was a good suggestion! Just one further question, is there any documentation or literature that's more modern i.e. in the last decade? Although the magazines and articles listed do have some good information, most of the fundamental technologies seemed to have been developed in and around the 1970s with little in the way of true technological progress. Even digital methods seem to do the basic things that analogue designs are doing, just with a longer memory.

[Qiaozhi]

Thanks, https://worldradiohistory.com was a good suggestion! Just one further question, is there any documentation or literature that's more modern i.e. in the last decade? Although the magazines and articles listed do have some good information, most of the fundamental technologies seemed to have been developed in and around the 1970s with little in the way of true technological progress. Even digital methods seem to do the basic things that analogue designs are doing, just with a longer memory.

Leonardo Ciocca from the Advanced Metal Detecting Research Lab (AMDTT) in Italy -> http://www.amdtt.it/ sent me a couple of books he had printed a few years ago:

You can get a free online copy of "A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining by Claudio Bruschini" here -> https://core.ac.uk/download/pdf/323031134.pdf
and "Advanced Metal Detectors by Dr. Serkan Aksoy" from here -> https://www.researchgate.net/publica...etal_Detectors
You could also look under Theory and Technique (Teoria e Tecnica) on the AMDTT site.

I don't think the printed versions are readily available for purchase, but it might be worth contacting Leo.

P.S. Also look under the Interviews (Interviste) section.

[CrizzyD]

Thanks Qiaozhi , Claudio I'm familiar with but I'm not familiar with the others. I'll take a look.

[Carl-NC]

A problem with this field is that, at the shallow end, there are magazine projects which offer almost no operational theory and, at the deep end, journal papers and patents which dive into advanced concepts with little in the way of basics. In between there is almost nothing, and that's the void ITMD and this forum attempt to fill. I will say that once you understand the basics, patents become a valuable source for getting into more advanced techniques, and you may have to go back to 30-40 year-old patents. Patents are notoriously hard to read, and it is critical to read the whole patent body (not just the claims) and often several times to parse it out.

[Qiaozhi]

A problem with this field is that, at the shallow end, there are magazine projects which offer almost no operational theory and, at the deep end, journal papers and patents which dive into advanced concepts with little in the way of basics. In between there is almost nothing, and that's the void ITMD and this forum attempt to fill. I will say that once you understand the basics, patents become a valuable source for getting into more advanced techniques, and you may have to go back to 30-40 year-old patents. Patents are notoriously hard to read, and it is critical to read the whole patent body (not just the claims) and often several times to parse it out.

Very true.
Also, the "advanced" papers are normally full of complex mathematics and difficult to follow, and quite often the results do not yield any practical result.
Modern digital metal detectors have their internal operation hidden in software so trying to figure out how they work is almost impossible unless you work for the company.

[CrizzyD]

and, at the deep end, journal papers and patents which dive into advanced concepts with little in the way of basics.

I actually find this to not necessarily be the case for me. I'm at present exclusively interested in PI and I can find maybe a dozen journals on IEEE and other places, and the majority of that is about demining and using other sensors to complement PI. Not at all anything about PI itself. Perhaps I've dismissed patents too readily, but this was something else that I found to be lacking in any real detail (as expected). I think that the general bulk of work has been on IB and your statements hold true on that but PI seems like a different beast. I'll definitely take another solid look at patents though, from your recommendation.

[Carl-NC]

I find that IB dominated patents up to 1990-ish, not so much since then. Here is a list of just Minelab PI patents:

US5506506
US5576624
US6636044
US6653838
US6686742
US6690169
US7474102
US7791345
US7924012
US8106770
US8614576
US9250348
US9348053
US9366779
US9429674
US9547065
US9829598

This does not include pending works. Also look up Carl V. Nelson, he had quite a few PI patents for Johns Hopkins.

It seems to me that most of the journal articles on metal detecting tend to focus on time domain, maybe because they like the math. And anything to do with demining is likely to be PI, maybe look further back before they started merging it with GPR.

If there is something particular you're looking for then let us know, maybe someone can help with that.

[CrizzyD]

Hi Carl thanks for the suggestions, I think I perhaps dismissed patents a bit too early. I've also gone a bit left-field and decided to look at manuals for some PIMD manufacturers to see what is claimed. I appreciate that I'm going a bit off topic here but I'd be interested to know your thought on the claims made by a Thermofisher Industrial MD.

PDF here, page 12 and 13:

https://www.thermofisher.com/documen...l-REC4479B.pdf

I think that we all know that for PI, the higher the magnetic permeability of a material, the bigger the response (i.e. longer delay in recovery). However that's just one piece of the puzzle. The magnitude of the response is also determined by geometry/surface area and distance from the coil(s). In the manual, they're claiming that they can discriminate between materials with PI just by changing the timing window of the sample delay. I can see this being true in a lab environment where all factors are identical aside from the material, but in a real-world scenario there is a variety of factors as mentioned. How true could their discrimination claim be as stated on p. 13?

[Carl-NC]

Like gold, iron responses can be all over the place. Small flecks of rotted steel cans will look like low conductors, boot tacks are medium-low, nails are medium-high, and bucket teeth (per their example) are high conductors. So, yes, you can use the delay to ignore some items.

[CrizzyD]

But what would be the difference between a bucket tooth that's 500mm from the coil and a can that brushes across the coil? Effectively a <5mm distance? Surely a simple delay method wouldn't take into account distance from the coil I guess is my point.

[Carl-NC]

If you have only one sample, then yes, you have no idea what is being detected. But as you increase the sample delay, low conductors will start to fall out and won't be detected, even if they are close. With 2 or more samples, you can determine conductivity and ignore low conductors even if they are detected.