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Target ID More About Target Size, Than Type Of Metal


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21 minutes ago, Erik Oostra said:

say 45 kHz for small shallow targets to bring the Equinox inline with the Gold Monster.. now that would be good..

Not enough difference between 40 and 45 kHz to matter. I ditched the Monster and kept the Nox for that very reason. The Monster was redundant.

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39 minutes ago, Steve Herschbach said:

Not enough difference between 40 and 45 kHz to matter. I ditched the Monster and kept the Nox for that very reason. The Monster was redundant.

And frankly there was not much difference between 4 and 5 khz when ML added it to Equinox in ver 3.0, per se.  Although small absolute changes in frequency at the low end can make a bigger difference in response (the 1khz change from 5 to 4 khz, would make more difference than at 1 khz change at 40 khz).  What was interesting, about adding 4 khz was that it seemed to run a lot quieter than 5 khz.  Primarily anecdotal, but if what folks were observing was more than just their imagination, then it could indicate ML was also potentially experimenting with a new signal processing or noise filtering algorithm.  Great way to beta test a feature without much risk because the 4 lhz was perceived as a bonus add on.  Of course it also added to the confusion regarding the frequency constituents of Multi-IQ because ML marketing conflated the 5 (now 6) single frequency options with the SMF frequency range with their infamous cloud diagram.

SmartSelect_20200812-222954_Drive.thumb.jpg.5b2fda78da1c2fa4910aeeb9910cd072.jpg

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Maybe more going on there I think than we know about, like 5 kHz not optimal as a multi pick? Both Nokta and XP picked 4 kHz. EMI?

4 to 40 in multi is becoming a thing.

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17 hours ago, PimentoUK said:

Likewise, the cupro-nickel alloy used in the US 5c coin, and many other world coins, is an especially lousy electrical conductor. It's widely used as electrical resistance wire, in heaters, kettles, hairdryers, electronics resistors. But it's 60% copper, not really what you'd expect.

Excellent post, PimentoUK.  I will make one small correction -- our USA 5 cent 'nickels' are 75% Cu.  I think that drives home your point even more.  As a sidelight, during WWII they changed the comp to 56% Cu, 35% Ag, 9% Mn (= manganese).  It's no coincidence that these Warnicks, when not adversely affected by leaching, give the same (or very close) dTID (at least on my ML Equinox) as the standard composition.  There was an intense(?) study done to match both the conductivity and density because vending machines that existed at the time were sensitive to one or the other, to prevent slugs from being accepted.  Manganese is one of the worst metallic elements for conductivity and when leached from those coins, results in higher dTID's.  (This last point is my speculation as there is evidence for such, but not rigorously proven to my knowledge.)

16 hours ago, Geotech said:

...Here is a graph I recently did for ITMD3 showing the conductivity of copper-nickel alloys, from pure copper to pure nickel.

Excellent!  Similar to data I've posted on gold-copper and gold-silver alloys which I found here and was posted in a couple places, including here.  I'm surprised you were able to get so many different alloys to create this plot.  Did you mix them yourself?

What I've never seen is a similar plot for copper-silver alloys.  You wouldn't happen to have that one?

conductivity_gold-alloys.png

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12 hours ago, Cascade Steven said:

Geotech:  I've been away from the forum for a while and just dropped in on this very interesting conversation.  I have a question about conductivity and apologize in advanced if I missed the answer elsewhere.  When you talk about conductivity of metals, do you refer to electrical conductivity or magnetic conductivity as in magnetic susceptibility?  Thanks

What Pimento said. All we're talking about here are eddy current responses which depend on electrical conductivity. Magnetic responses (soil & iron) involve susceptibility and BH curve hysteresis. Most iron also have eddy responses which complicate things even more.

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28 minutes ago, GB_Amateur said:

I'm surprised you were able to get so many different alloys to create this plot.  Did you mix them yourself?

What I've never seen is a similar plot for copper-silver alloys.  You wouldn't happen to have that one?

Data came from the CRC Handbook of Chemistry & Physics. I've looked all over for similar data for copper-silver alloys but haven't found any.

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On 1/20/2022 at 8:52 AM, Steve Herschbach said:

 

Think of frequency, whether single frequency, or a mix of frequencies, in terms of the desired target size, offset by the added ground/salt response. Think of the target id scale as a size scale, low numbers are small targets, high numbers large targets. Think less about it being an indication of type of metal. Aluminum responds anywhere on the scale. So does gold, lead, silver, copper. Small foil a low single digit, and aluminum can like a silver quarter. Pick your frequency mix and your target id numbers to match the size of the targets you are seeking, and life will get easier. And quit thinking of multifrequency in terms of finding more targets better the more frequencies you use. Nonsense, just marketing nonsense.

 

 

Flash card for test tomorrow...Thanks for a good read Steve

strick

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3 hours ago, PimentoUK said:

Copper and silver seem pretty compatible, maybe the alloy curve is rather dull, hence not worth studying?

That's not been my experience with scientific data.  There's a plethora of boring data out there.  :biggrin:

 

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  • Steve Herschbach changed the title to Target ID More About Target Size, Than Type Of Metal

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