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  • #91
    When you are properly "provoked" with questions; you give phenomenally good and easy to understand answers!
    Just the kind of answers, written in a way that suits laymen and is easy to understand.
    This is exactly the style you should use when writing books.
    Because with your two explanatory posts; I learned more easily and quickly than if I had read 200 posts by other "experts" or some highly technical book written by someone (nerd) and aimed at people like him.
    I think you were born to be a good teacher. You just need to adapt your narrative to the wider population.
    To get out of the box of a strict techno-nerd (I don't think you are one, but there are plenty of them around us).
    I mean this honestly and I'm very serious this time, I'm not kidding. Use that gift of yours and this suggestion of mine and you will write the best books.
    I've never delved too much into the details of PI detectors. And now in a couple of posts I have learned a lot of what I was interested in.
    Admittedly, it would be too ambitious to say now that everything is clear to me, of course it is not.
    But I finally understood some things and now I understand some methods, processes and techniques better.
    Further... let me tell you what I would like to see explained in more detail,
    not so much from the theory side; but from the side of practical performance.


    "...Their curvatures are different. Iron targets exhibit a collapsing B-H curve response, which also looks different. If you grab a minimum of 3 points then you can distinguish these curves..."

    That process will happen mostly in the processor code.
    Well, you can answer me by giving an example of program "filters", procedures and functions that will do it. But that's not the point.
    It won't mean much to me at this point, later maybe, probably will do, once I figure out my development&prototyping system and start dealing with code solutions.
    Imagine that you have to do the same task from your quoted text in a completely analog technique, using opamps and cmos chips and explain it that way.
    Thanks in advance!

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    • #92
      Originally posted by green View Post

      I joined this site a few years back. Owned a Heath kit VLF metal detector that we used to find arrows hidden in the grass that missed the target long time ago. I joined to learn something about metal detectors and picked PI. Had health problems about a year ago and haven't played with the metal detector since. Trying to follow this discussion. When I was active, I made a few detectors that kind of worked. What I missed was a test that I could compare my detector against some commercial or other detector. Mostly played trying to detect gold since it looked like the most difficult. Have some gold nuggets for testing. Problem was they all test different. Tried to find a test target that anyone could obtain. Tried aluminum foil (not all foil is the same thickness, TC effected by thickness and how accurate foil target was cut). Tried lead shot from shotgun shells (quite a bit of variance, maybe do to size or not being pure lead). Copper electrical wire tests consistent and suggested it could be used for a test target (TC not effected by length, amplitude is affected by length but should be able to cut accurate enough to not matter if pieces are cut 5 10 15 or 20mm. Wondering if anyone has found a good target for testing while I've been gone.
      Click image for larger version

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      ​​ (TC) 4grain (3.1us) 10grain (6.7us) 18grain (5.7us)
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      Hi green, nice to see you back. Your table with testing targets is very interesting. It is probably the best we have seen so far.
      Time ago you were experimenting with the Moodz bipolar square wave. I remember your observations about the TX slope. Did you try an actual hardware circuit? I would be very interested to hear how it behaved with your figure 8 coil.

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      • #93
        I did try a actual bipolar circuit. Not sure which schematic used. Probably not Moodz circuit, just something to try Click image for larger version

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        • #94
          Here is the preamp for the AMX RX, as tested on a breadboard.
          The scope picture of the output of the preamp with a DD coil.
          The DD coil is shown at the AMX coil thread still open so you can see the insides as well as the specifications and the type of wires used.

          Click image for larger version

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