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Seems this thread has diverged; @Valens Legacy implies that the equinox should detect magnesium containing bones such as teeth or walrus tusks, while @Steve Herschbach points out that non-conductive items will generally be invisible to the EM search of a detector unless they coincide with a void that alters the ground signal. At the very minimum I can report that the equinox does not in fact detect my cat in any obvious way, even at the highest sensitivity. I think a third possibility exists; perhaps snakes are not generally detectable, which is what you would expect, but these snakes were tagged somehow, perhaps for research and tracking purposes. 

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Why is my credibility detector sounding off louder than my metal detector?

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5 hours ago, ShintoSunrise said:

I think a third possibility exists; perhaps snakes are not generally detectable, which is what you would expect, but these snakes were tagged somehow, perhaps for research and tracking purposes.

Interesting hypothesis.  I did a bit of web searching and snakes are sometimes tagged with RFID chips.  Here is a general overview of that technique (not limited to snakes).

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The presence of a metallic element does not mean there will be a response to a metal detectors.  Most minerals contain metallic atoms but most minerals don't set off a metal detector.  Take halite for example.  Halite's common name is rock salt -- a compound made up of a metal (sodium) and a non-metal (chlorine).  Common table salt is a pure form whereas rock salt typically has contaminants mixed in.  I just ran my Equinox over a chunk of halite maybe half the size of a golf ball.  In order to run at high gain (24) I had to use single frequency since I'm at home with lots of EMI around, even in my back yard where I did the test.   All channels notched in and 10 kHz, 15 kHz, 20 kHz, and 40 kHz (EMI quiet frequencies here) all gave no reaction with coil swing about 1 inch or less over the sample.

Metal detectors respond to two things -- ferromagnetic materials and conductors.  The mineral magnetite is an example of a ferromagnetic non-conductor and is well known to cause a signal in an IB/VLF detector.  Metal detectors are sensitive to conductors because the transmitted changing magnetic field from the detector causes an eddy current of charges to flow in the conductor.  In metals those charges are free electrons ('free' in the sense that they aren't bound to any atom).

Ions in solution are also free to move -- that's part of the mechanism in a battery.  Disolve halite in water the sodium and chlorine atoms (sodium carrying one less electron than when neutral and chlorine carrying one more -- thus meaning each one has a net charge) are available to move in solution.  Thus wet salt (e.g. a wet saltwater beach) causes problems for an IB/VLF metal detector.  That's also why some sensitive detectors sound off when you wave your hand closeby (mentioned by Jeff McC.) -- conductive ions from salts on your less than perfectly dry skin.  Damp salty ground in deserts is another example of false signals that IB/VLF's can pick up.

There is a practical limit for something that conducts to be sensitive to a detector, though.  Lightning often strikes trees because they are the least resistive path to ground in a particular location, but I don't think trees set off a metal detector, at least in general.  I swing over large roots and in my soil I don't get signals unless there are metals hiding in or under them (and that does happen occasionally 😁).

Steve H. mentioned ground voids as setting off a detector because the ground balance was matched to solid ground of more/less uniform mineralization and a void is effetively an anomaly -- some of the ground being missing.  I recall reading (can't remember exactly where) Charles Garrett mentioning this in one of his books -- that tree roots can lead to false signals since the root itself displaces ground.  I think you need rather highly mineralized ground for this to show up, though.  As I noted above, in my moderate (2-3 bars or mid-scale on the Fisher F75 and Fisher Gold Bug Pro) ground I don't get falsing going over roots.  Ditto when swinging over mole trails.

 

 

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11 minutes ago, GB_Amateur said:

The presence of a metallic element does not mean there will be a response to a metal detectors.  Most minerals contain metallic atoms but most minerals don't set off a metal detector.  Take halite for example.  Halite's common name is rock salt -- a compound made up of a metal (sodium) and a non-metal (chlorine).  Common table salt is a pure form whereas rock salt typically has contaminants mixed in.  I just ran my Equinox over a chunk of halite maybe half the size of a golf ball.  In order to run at high gain (24) I had to use single frequency since I'm at home with lots of EMI around, even in my back yard where I did the test.   All channels notched in and 10 kHz, 15 kHz, 20 kHz, and 40 kHz (EMI quiet frequencies here) all gave no reaction with coil swing about 1 inch or less over the sample.

Metal detectors respond to two things -- ferromagnetic materials and conductors.  The mineral magnetite is an example of a ferromagnetic non-conductor and is well known to cause a signal in an IB/VLF detector.  Metal detectors are sensitive to conductors because the transmitted changing magnetic field from the detector causes an eddy current of charges to flow in the conductor.  In metals those charges are free electrons ('free' in the sense that they aren't bound to any atom).

Ions in solution are also free to move -- that's part of the mechanism in a battery.  Disolve halite in water the sodium and chlorine atoms (sodium carrying one less electron than when neutral and chlorine carrying one more -- thus meaning each one has a net charge) are available to move in solution.  Thus wet salt (e.g. a wet saltwater beach) causes problems for an IB/VLF metal detector.  That's also why some sensitive detectors sound off when you wave your hand closeby (mentioned by Jeff McC.) -- conductive ions from salts on your less than perfectly dry skin.  Damp salty ground in deserts is another example of false signals that IB/VLF's can pick up.

There is a practical limit for something that conducts to be sensitive to a detector, though.  Lightning often strikes trees because they are the least resistive path to ground in a particular location, but I don't think trees set off a metal detector, at least in general.  I swing over large roots and in my soil I don't get signals unless there are metals hiding in or under them (and that does happen occasionally 😁).

Steve H. mentioned ground voids as setting off a detector because the ground balance was matched to solid ground of more/less uniform mineralization and a void is effetively an anomaly -- some of the ground being missing.  I recall reading (can't remember exactly where) Charles Garrett mentioning this in one of his books -- that tree roots can lead to false signals since the root itself displaces ground.  I think you need rather highly mineralized ground for this to show up, though.  As I noted above, in my moderate (2-3 bars or mid-scale on the Fisher F75 and Fisher Gold Bug Pro) ground I don't get falsing going over roots.  Ditto when swinging over mole trails.

 

 

Great analysis and I agree 100%. Very difficult here to explain why the equinox would detect a snake as a matter of course without introducing metal detecting concepts that don't jive with either physics or our daily experience; I'm going to stick to my tagging hypothesis unless someone else jumps in with another explanation. I saw in another post someone stating their equinox was detecting crabs at the beach; I can only guess that is explainable by unseen tagging or the void hypothesis. At least if I had a snake handy I could settle this right now but unfortunately I am fresh out! 

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5 hours ago, GB_Amateur said:

that tree roots can lead to false signals since the root itself displaces ground.  I think you need rather highly mineralized ground for this to show up

Seen it myself many times.

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When I first gave a response to the question I did a search on the internet and came up with the information I had given. Several articles stated the same thing that I had read also. I did not think of the void that the snake had made, and it sounds like the best answer to the question.

Here is a small part of what I had read from one of the articles.

"Mineralized tissues, such as bone, teeth, antler and horn, are important elemental storage sites in animals. These tissues contain necessary elements, both major, such as calcium (Ca), phosphorus (P), magnesium (Mg) and sulphur (S), and trace elements, such as iron (Fe), zinc (Zn), manganese (Mn) and cadmium (Cd). Most elemental research has focused on the major elements, especially Ca, P, Mg, due to their crucial role in bone metabolism [1]. However, other elemental evaluations and comparisons across tissue types and species are required to more fully understand their biological function."

That is why I made my comment thinking that if a snake was coiled up in such a small ball that it might be possible for a detector to maybe pick it up.

Since I am new at detectors I hope this explains why I gave the answer that I gave.

 

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16 hours ago, ShintoSunrise said:

Very difficult here to explain why the equinox would detect a snake as a matter of course without introducing metal detecting concepts that don't jive with either physics or our daily experience; I'm going to stick to my tagging hypothesis unless someone else jumps in with another explanation.  (emphasis mine)

This is another key point in the investigation of this strange occurrence.  On this forum alone there are millions of hours of detecting experience.  (Not everyone has read this post, but still a lot of combined experience by its viewers.)  Further, a story like this will propogate in the community -- at club meetings, in hardcopy magazines (when we used to have those 😁), on Facebook, on other internet pages and forums....  My participation in this hobby has been mostly confined to reading in the distant past and recently (last 5 years) on the internet, mostly here.  Has anyone seen/read of a similar occurrence?  (You did mention crabs.)

You pointed out that the signals you received were in the pulltab range although you didn't say how tight they were.  If 'sharp' (meaning in space -- not an extended target) and fairly consistent in TID, that would be further evidence of a uniform metal object such as possibly a passive integrated transponder (PIT) tag you hypothesized previously.  (I don't know if those actually have enough conductor to set off a detector.  Could a detector's signal set them off?  Again, more info needed.)  Large animals sometimes are tagged with larger but simpler things -- there was a thread here about bird wildlife tags a while back -- but I doubt those would be used on snakes.

I understand your feelings about accidentally killing one.  But on the plus side, if you decide to avoid this signal in the future at least you'll save yourself digging a lot of worthless pulltabs.  😏

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