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  • Basics: Recovery Speed, Reactivity

    Somewhere on the net i found this:

    "...Recovery speed refers to the time it takes a detector to recover from identifying a ferrous object and signal the presence of a non ferrous target...."

    This is something we can agree on.

    All of us do understand what "Recovery speed" is.
    But what defines Recovery Speed at given design? What factors?
    Working frequency?


    "...You will note that all detectors have a frequency rating. This will fall into one of three categories: Low frequency (1-6kHz), medium frequency (7-15kHz) and high frequency (16-19kHz). In simple terms the low frequency models are regarded as being the deeper seeking machines that handle iron and mineralisation well but are not the best in terms of recovery speed . In contrast, the higher frequency machines have faster recovery speeds and are particularly good with smaller and thinner targets. Most introductory metal detectors fall into the middle frequency bracket...."

    This quote implies that most deciding factor is working frequency!
    Is it?
    I do recall some models with low working frequencies and yet very descent Recovery Speed and on other side some models with high working frequencies and not so good Recovery Speed. Intentionally i will avoid to mention exact models.
    Point is that working frequency is not most deciding factor for good Recovery Speed.
    What makes fast Recovery Speed at given metal detector design?
    For example we can take some of existing projects from this forum and analyze circuitries.
    For example we can take TGSL, Classic, Magnum, Musketeer etc..etc..
    What are the parts that may define/affect Recovery Speed at those designs?
    Just a starting hint: Musketeer's working frequency is 5kHz, TGSL's is 14,6kHz, Classic's is 6.5kHz.
    Yet Musketeer is having much faster (better) recovery speed than TGSL and Classic together!
    How come?
    What have to be modified and improved at TGSL, Classic... to improve their Recovery Speed?
    ...
    I think such questions are more interesting and relevant here for majority of members than anything else.
    With this, "Basics" characterized, title of thread i would like to provoke series of similar articles which will describe main features of one conventional design.
    I am sure such articles will be more beneficial and educative for majority of us than just plain posting of various schematics, more or less complicated and more or less interesting.
    Also i suggest Administrators to dedicate separate part of forum to these "Basics" threads in which various "Basics" fundamental principles will be explained and well elaborated.
    Using some simple and straightforward design, schematic, we can "walk" from component to component, from stage to stage and elaborate all the aspects of their roles there.
    Can it be done different than is done?
    Can it be improved?
    What would be advantages and disadvantages if we do it like this... like that... etc...
    If my suggestion is accepted, than i also suggest Classic schematic to be a working example.
    Because is tough to find more straightforward design than it is (and it has poor Recovery Speed anyway, so why not improving it also).


  • #2
    I have done many tests with the integrated circuits 4066,4016,4053 ... and the FET BF245, 256, etc and all that I've noticed that most recovery rate is up to the 4053. I built the SMW, TGSL, IGSL, CLASSIC, MAGNUM, and many more, but I have come to the conclusion that the detectors carrying the 4053 had a higher recovery rate than those who did not use the go Integrated circuit.

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    • #3
      Originally posted by eduardo1979 View Post
      I have done many tests with the integrated circuits 4066,4016,4053 ... and the FET BF245, 256, etc and all that I've noticed that most recovery rate is up to the 4053. I built the SMW, TGSL, IGSL, CLASSIC, MAGNUM, and many more, but I have come to the conclusion that the detectors carrying the 4053 had a higher recovery rate than those who did not use the go Integrated circuit.
      So actually you are thinking that speed of switching at synchronous demodulators is actually a main factor which defines Recovery Speed at that detector?
      Ok, maybe a partial true, but i would not place bet on it.
      How about channels? Each of those including a network for computing and holding average signal value, for a predetermined length of time?
      Let's compare two opposite cases: TGSL is having fets as switches at synchronous demodulators and Musketeer is having 4066 there.
      Yet Musketeer is having better Recovery Speed than TGSL?
      How to explain that?
      Even worse: Musk ticks on only 5kHz while TGSL ticks on 14.6kHz!

      Comment


      • #4
        An example:
        I built the SMW and the Classic.
        The SMW has the 4053, and the classic 4066 or 4016.
        The SMW has a recovery rate higher than the Classic.
        You as you explain this?

        Comment


        • #5
          Originally posted by eduardo1979 View Post
          An example:
          I built the SMW and the Classic.
          The SMW has the 4053, and the classic 4066 or 4016.
          The SMW has a recovery rate higher than the Classic.
          You as you explain this?
          Yes SMW looks like is having faster recovery speed. But i think it is because of its "loose" discrimination rather than because of 4053 use there.
          Next thing at SMW is audio stage based on NE555 which is giving sharp and "fast" response that may fool observer to think that detector is having ultra fast Recovery speed.
          "Loose" discrimination circuitry will allow Fe and Nonfe signals to pass together in some cases and it will look as it is fast Recovery speed.
          We can go with this in wrong direction. More productive would be if we pay more attention on channels there and their role in Recovery speed.

          Comment


          • #6
            Must admit i am very disappointed with interest for this subject.
            I thought this will attract huge attention among local forum experts here and that i will get bedlam of various answers and explanations from those.
            More surprised am because i asked here most crucial question relating modern metal detectors features.
            Seem nobody really knows what is all about and what is indeed Recovery Speed in technically speaking?? How to achieve faster and slower recovery speed at one simple and straightforward design as suggested Classic or similar.

            Bit a disappointed...must say...
            Ciao ragazzi!

            Comment


            • #7
              Small addition: while Minelab Explorer is offering adjustments : Fast and Deep recovery, and XP Deus are offering Reactivity (Recovery Speed) adjustable from 0 to 5 - yet we here on these forums are not able to understand nor to explain what electronic function actually is Recovery Speed. What stages at detector do forms it and affects it etc...etc...


              Ain't that a shame?

              Comment


              • #8
                You are giving too much credit for marketing science. Perhaps they initially wanted to call it doohickey, but recovery speed sounded somehow more scientific or snappier

                Just give them a break.

                Comment


                • #9
                  Sorry Ivconic, it was work time for me. Now it's fun time!

                  Recovery speed isthe time it takes a detector to recover from identifying any target and signal the presence of another target.

                  Demod design and filter speed usually dictates this. The reason a 4053-based circuit seems to perform better is that it is usually a full-wave demod, whereas a 4066-based circuit is usually a half-wave demod.

                  - Carl

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                  • #10
                    In my Classic IDX, I will replace the 4066 by 4053 and see what happens. I have to make some changes to the operational preamplifier output RX. After the NE5534, I have to insert a dual operational amplifier to connect the two outputs to the inputs of 4053. I have really wanted to try that again. In the past I have done this experiment and really worked.

                    Comment


                    • #11
                      I have tried to modify the old Classic. Take a look to see what you think. I hope there are no errors. Greetings to all.
                      Attached Files

                      Comment


                      • #12
                        Originally posted by eduardo1979 View Post
                        I have tried to modify the old Classic. Take a look to see what you think. I hope there are no errors. Greetings to all.
                        The level on OA input (TL072, pin 3) is flying in the air.

                        Comment


                        • #13
                          Originally posted by holyuser View Post
                          The level on OA input (TL072, pin 3) is flying in the air.
                          PIN 3 is connected to C 4. I do not see flying in the air.

                          Comment


                          • #14
                            Originally posted by eduardo1979 View Post
                            PIN 3 is connected to C 4. I do not see flying in the air.
                            I mean, it must be tied to some constant level, in example to 1/2 VDD.

                            Comment


                            • #15
                              Originally posted by holyuser View Post
                              I mean, it must be tied to some constant level, in example to 1/2 VDD.
                              I think you mean this. I am right now.
                              Attached Files

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