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Speaker 1: Get in touch with technology with tech Stuff from how

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Speaker 1: stuff Works dot com. Hey there, and welcome to tech Stuff.

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Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with

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Speaker 1: How Stuff Works in love all things tech and back

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Speaker 1: on October two thousand eleven, my co host Chris Paulette

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Speaker 1: and I sat down in a tiny little alcove at

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Speaker 1: the then headquarters of How Stuff Works in Buckhead, Georgia, Buckhead, Atlanta.

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Speaker 1: I'm kind of glad we're not in that particular alcove

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Speaker 1: now I'm in a much nicer studio. But we sat

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Speaker 1: down to talk about how metal detectors work. What is

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Speaker 1: the operating principle behind metal detectors, what's the science behind it.

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Speaker 1: So you're about to enjoy this classic episode of tech

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Speaker 1: Stuff how metal detectors work, And I'll talk to you

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Speaker 1: again in just a moment. So today we are going

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Speaker 1: to talk about this. You know what, This was a

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Speaker 1: topic that I don't know that anyone has ever requested. Um.

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Speaker 1: It came to me actually as I was looking through

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Speaker 1: stuff in my basement and went metal detectors. How should

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Speaker 1: talking about We've never talked about metal detective Actually, we've

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Speaker 1: sort of talked about metal detectors, because metal detectors use

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Speaker 1: a lot of the technology we talked about before, especially

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Speaker 1: the relationship of magnetism to electricity. Yeah, um, but yeah,

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Speaker 1: I mean it's something that we run into very often,

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Speaker 1: especially if we travel and walk through the metal detectors

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Speaker 1: at the airport. If we're not getting back scattered or uh,

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Speaker 1: you know, dropping stuff that you can't find, losing your

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Speaker 1: wedding ring and the malts outside. Yikes, that's good stuff.

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Speaker 1: I've done that. I still have it, so there you go.

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Speaker 1: I've never lost my wedding ring. All right, Well it

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Speaker 1: was only temporary. So anyway, metal detectors talk about what

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Speaker 1: they are. We're mostly going to be talking about the

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Speaker 1: kind that you would you would care you with you

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Speaker 1: you know, the portable metal detectors that you would use

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Speaker 1: when looking for say, loose change on the beach, or

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Speaker 1: you know, searching for that rare civil war uh bullet

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Speaker 1: or a gun that might be part of you know,

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Speaker 1: in an area that you knew the battle happened here,

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Speaker 1: so there may very well be stuff here. Yeah. We

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Speaker 1: we should definitely talk about some of the applications of

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Speaker 1: the technology. Um, and I would like to point out

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Speaker 1: that we have an excellent article on how stuff works

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Speaker 1: dot com if you're interested in learning more, um, how

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Speaker 1: metal detectors work. Yeah, it should be pretty easy for

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Speaker 1: people to find, written by Jeff Tyson, and it is

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Speaker 1: a very good article and very uh simple to follow,

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Speaker 1: easy to understand. I would say this is this is

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Speaker 1: one of those really great how stuff works articles. Yeah.

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Speaker 1: You know, by the time you get through it and

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Speaker 1: you're like, oh, yeah, no, that totally makes sense, especially

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Speaker 1: if you have a little bit of grounding in the

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Speaker 1: way electromagnetism works and conductors and inducers. Right, So we'll

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Speaker 1: we'll cover that. I mean, we've talked about an in

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Speaker 1: previous podcast, but we'll we'll do a quick brush up

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Speaker 1: so that we can explain it. Um, so you wanna,

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Speaker 1: let's let's talk about the the Jeff does a great

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Speaker 1: job at breaking down what the typical portable metal detector,

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Speaker 1: the four main parts of one, what they would be. Yeah,

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Speaker 1: I mean, if you've ever seen people walking around with

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Speaker 1: a metal detector, you you sort of know what they

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Speaker 1: look like. They have a round dish part that's used

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Speaker 1: close to the ground, right, that's a that's called the

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Speaker 1: coil um then yes, And then you have the stabilizer um,

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Speaker 1: which is the part that you actually hold onto, that

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Speaker 1: holds onto europe, that that you see on your arm

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Speaker 1: because you know, frankly, having used a metal detector, it's

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Speaker 1: not the lightest thing, right. This this helps, This helps

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Speaker 1: distribute the weight somewhat so that you're not you don't

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Speaker 1: feel like you're carrying around a you know, ten pound

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Speaker 1: brick the whole time, because without that then you would

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Speaker 1: get very tired very quickly. Yeah. And the the ten

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Speaker 1: pound the aforementioned ten pound brick, which probably isn't ten pounds,

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Speaker 1: but it certainly can feel that way after a while.

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Speaker 1: That's the control box, uh, And you've got all your

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Speaker 1: your electronics in there. And and then the the connecting bit, yes,

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Speaker 1: the long skinny part that's the shaft. Yes, it connects

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Speaker 1: the coil at the base to the part that you're holding,

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Speaker 1: and the of course the control box. So those are

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Speaker 1: your four basic parts of your basic metal detector. Yes.

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Speaker 1: And then you know you have your headphones because this

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Speaker 1: is one of our episodes of stuff that beeps and

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Speaker 1: stuff what beats? Stuff? What beeps and it it does

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Speaker 1: in fact deep Yeah, there's usually some sort of audible

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Speaker 1: alert that you have in fact detected metal and now

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Speaker 1: and more sophisticated UH, metal detectors will tell you a

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Speaker 1: lot more often with uh, well sometimes with with an

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Speaker 1: audible tone, but also with a visual uh, some kind

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Speaker 1: of visual analysis. We can get into that to in

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Speaker 1: a minute. So there are three main types of metal detectors,

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Speaker 1: the ones at work, the three three main approaches to

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Speaker 1: to metal detection. Let's say, Uh, there's UM, there's the

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Speaker 1: very low frequency which is probably the most um, the

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Speaker 1: most popular or the most common type of MEL detector,

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Speaker 1: at least for the portable metal detectors. UM. Yeah. When

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Speaker 1: we get into this, you'll you'll see that each of

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Speaker 1: these different types has its own strengths and weaknesses. And

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Speaker 1: you might say, well, the VLF detector sounds great, why

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Speaker 1: would you use the others? We'll get into that. Yeah.

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Speaker 1: The other two are pulse induction and beat frequency oscillation. Yeah.

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Speaker 1: I I knew a beat frequency oscillator once. He was awesome. Anyway,

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Speaker 1: I think there was something else I guess, So, yeah,

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Speaker 1: that's the beat boxer frequency oscillator. That the uh, the

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Speaker 1: VLF metal detector is the type that I have. UM,

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Speaker 1: and uh the the basic differences, uh, and these is

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Speaker 1: you know, you'll see those really in the coils. To

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Speaker 1: be honest, because the VLF has two different coils. One

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Speaker 1: transmits um and and the other is basically an antenna

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Speaker 1: to pick up the signals, so they're shielded from one another,

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Speaker 1: so it doesn't pick up because otherwise you turned it on,

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Speaker 1: you would just have the receiver saying, oh my gosh,

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Speaker 1: there's metal everywhere. Holy crap, you're rich, even up in

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Speaker 1: the air. It's it's literally everywhere. Yeah, that would that

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Speaker 1: would not be very useful. And taking this back to

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Speaker 1: the store where I bought it. It's a detector detector.

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Speaker 1: This does not do me any good. It's a detected

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Speaker 1: or it's a detected or where's perry? So the the

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Speaker 1: the transmitter coil um it's it think of a circle,

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Speaker 1: all right. It's the circular part at the base of

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Speaker 1: the male detector. And if you were to take it apart,

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Speaker 1: which I do not recommend you do, you would see

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Speaker 1: that there is a warrant point your warranty and it

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Speaker 1: may not work anymore. You will have a there's a

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Speaker 1: coil of wire that goes around the perimeter of this circle.

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Speaker 1: Like it's it's wrapped around. So the circle itself is

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Speaker 1: let's say it's like a quarter of an inch thick,

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Speaker 1: and you've got this coil of wire that's that's coiled

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Speaker 1: around this quarter of an inch all the way around

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Speaker 1: the perimeter of this circle. When you run electricity through

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Speaker 1: this coil of wire, what happens besides the fact that

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Speaker 1: electrons are moving through because of the nature of electricity

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Speaker 1: and magnetism, Well, when you run electricity around a coil

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Speaker 1: like that, it generates a magnetic field. That's right, It

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Speaker 1: does generate a magnetic field, and it generates a magnetic

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Speaker 1: field perpendicular to the direction of the electricity. It's just

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Speaker 1: the nature of electromagnetism. It's amazing, it's awesome. That's what

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Speaker 1: how electro magnets work and UH dynamo's work in UH

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Speaker 1: and sort of using this reverse um. So you've got

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Speaker 1: electricity flowing through these coils, and that generates the magnetic field. Well,

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Speaker 1: it doesn't just the electricity. Electricity doesn't just flow in

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Speaker 1: one direction, no, it it goes back and forth. It

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Speaker 1: alternates very very very fast, almost as fast as I

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Speaker 1: waffle back and forth on what I want to eat

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Speaker 1: for lunch. And that means that the magnetic field also alternates.

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Speaker 1: The direction of the magnetic field changes. Uh And if

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Speaker 1: you think of it in terms of the disc, the

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Speaker 1: the coil disc being towards the ground, you can think

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Speaker 1: of it as the magnetic field occasionally is pushing against

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Speaker 1: or pulling the ground in general. That just think of

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Speaker 1: it that way. That's the direction of the magnetic field

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Speaker 1: while the electricity is going around and around in a circle,

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Speaker 1: back and forth and in the various directions, and that

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Speaker 1: alternation is happening hundreds of times per second. So you've

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Speaker 1: got this magnetic field that's that's just oscillating essentially right

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Speaker 1: there against the ground. When it comes to contact with

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Speaker 1: something that is metal, well, the metal will start to

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Speaker 1: that magnetic field will cause a a weaker magnetic field

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Speaker 1: to generate around the metal object. Yeah. Basically induces a

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Speaker 1: magnetic field in a metal object in the ground. So

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Speaker 1: let's say, uh, um, you drop a screw and when

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Speaker 1: you're trying to build something outside and you're trying to

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Speaker 1: find it with your metal detector so that you don't

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Speaker 1: step on it with a bare foot, and you know,

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Speaker 1: need a trip to the hospital and a technis shot. Um.

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Speaker 1: So as soon as you run the coil of the

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Speaker 1: field and you're not trying to touch the ground with it,

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Speaker 1: you really just need it close to the ground. Um,

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Speaker 1: it will find the screw. The screw will basically start

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Speaker 1: inducing a It will metal detect detector will generate a field,

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Speaker 1: and that will cause the screw to generate its own

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Speaker 1: a weaker magnetic Yeah, yeah, considerably weaker, but it will

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Speaker 1: the metal detector, Uh, the antenna coil and the transmitter

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Speaker 1: coil will say, oh, look there's something right there that

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Speaker 1: is generating a magnetic field. It's right here. Chris and

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Speaker 1: I have a lot more interesting things to say about

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Speaker 1: metal detectors, but first let's take a quick break to

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Speaker 1: thank our sponsor. So, if you have a coil of

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Speaker 1: wire and you introduce it into a fluctuating magnetic field,

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Speaker 1: that will induce the flow of electricity within the wire.

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Speaker 1: Just as electricity and the wire will create generate a

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Speaker 1: magnetic field, a magnetic field will induce electricity to run

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Speaker 1: through wire fluctuating magnetic field. It can't just be just

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Speaker 1: a magnetic field. So when the weak magnetic field from

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Speaker 1: the mental object hits that that the wire in the

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Speaker 1: the the the receiver coil that generates electricity which then

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Speaker 1: alerts the control box and that that's what. Then when

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Speaker 1: the control box gets an electric signal from the receiver coil,

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Speaker 1: that says beep, something is here, stuff, what beeps? Yep? Stuff?

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Speaker 1: What beeps? So yeah, that's the basic uh way that

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Speaker 1: a VLF metal detector works. It shoots out this magnetic field.

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Speaker 1: The polarization is alternating the same as the the flow

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Speaker 1: of electricity around the the the transmitter coil, and then

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Speaker 1: the receiver coil picks up any magnetic fields generated by

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Speaker 1: metal objects that are under the surface of the ground.

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Speaker 1: It's pretty cool and generally it will go more or

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Speaker 1: less about a foot. Yeah, you're not gonna find you know,

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Speaker 1: the Earth's core. Yea with a metal detect and the

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Speaker 1: depth of what the depth of the The effectiveness of

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Speaker 1: this metal detector is also going to be dependent on

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Speaker 1: other factors, like the nature of the metal object itself,

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Speaker 1: because some some metal objects are going to generate a

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Speaker 1: stronger magnetic field than others, like iron. Uh. It will

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Speaker 1: also depend on the composition of the soil. Yes, so

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Speaker 1: the soil has a lot of elements in it that

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Speaker 1: would create a magnetic field, you're gonna get a lot

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Speaker 1: of interference, yeah, or or an environment where uh that

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Speaker 1: that would conduct electricity more readily, Like if you were

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Speaker 1: trying to look for something and say saltwater, you might

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Speaker 1: have more difficulty than if you were looking, you know,

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Speaker 1: on on a different type of soil. UM. Now there

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Speaker 1: is something to uh called phase shifting, Yes, and that's

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Speaker 1: how it's able to tell what sort of metal, what

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Speaker 1: sort of metal it is, UM. And it really has

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Speaker 1: to do with the the inductance and the resistance of

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Speaker 1: the object that you're looking for. Now, the inductance is

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Speaker 1: um the objects ability to conduct electricity UM. And if

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Speaker 1: it's inductive, it will be able to to conduct electricity easily,

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Speaker 1: but it's slow to react to changes in the electrical current. UM.

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Speaker 1: If it's resistive, it doesn't conduct electricity is easily, but

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Speaker 1: it is quick to react to those those changes. And

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Speaker 1: a sophisticated metal detector will be able to tell you, well,

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Speaker 1: that's I think that's gold or based upon that phase shift,

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Speaker 1: because the face shift for a particular element is going

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Speaker 1: to remain constant, you know. That's that's why if it

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Speaker 1: didn't remain constant, then this wouldn't matter at all because

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Speaker 1: it wouldn't you know, we wouldn't know, you know, It's

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Speaker 1: like we just know something is down there, we wouldn't

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Speaker 1: know have any way of guessing what it is. But

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Speaker 1: because it's an inherent property of this particular material and

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Speaker 1: it's really dependent upon the molecular composition of whatever that

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Speaker 1: material is, UM, then we can make start making guesses

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Speaker 1: based on that phase shift. UM. And it's yeah, the

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Speaker 1: face shift, you know, with it being that difference in

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Speaker 1: timing between the transmitters frequency uh and the frequency of

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Speaker 1: the magnetic wave that's generated by the object. Um. You know,

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Speaker 1: it's these are sort of ranges, right like if it

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Speaker 1: if it's a certain range there, then the male detector

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Speaker 1: can give a best guess as to what that material maybe.

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Speaker 1: So there's never necessarily a guarantee that whatever it is

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Speaker 1: you've detected is specifically going to be you know, aluminum

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Speaker 1: versus goal or whatever. But it's a it's an indicator,

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Speaker 1: so that uh, it gives you at least the idea

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Speaker 1: of you know, is that you measure risk versus reward,

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Speaker 1: the risk of exhausting yourself digging up useless junk versus

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Speaker 1: the reward of possibly finding something that is of true value.

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Speaker 1: So that's really the whole purpose of this anyway. It's

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Speaker 1: just you know, to kind of tune in on that

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Speaker 1: beep and make it more meaningful so that you know,

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Speaker 1: you don't waste your time digging up uh little pull

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Speaker 1: tabs from soda cans. Yeah. Now, yeah, if you have

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Speaker 1: a higher inductance, it's going to create a larger phase shift,

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Speaker 1: and lower inductance has a smaller phase shift. Now, Uh,

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Speaker 1: metal detectors use a phase demodulator to read this, and uh,

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Speaker 1: what that creates is discrimination. Yeah, yeah, I know it's terrible,

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Speaker 1: but oh no, not that. Within metal detectors, it's okay, Yeah,

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Speaker 1: because the thing is a good metal detector will allow

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Speaker 1: you to filter out stuff that you don't want because

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Speaker 1: the metal detector, if you said it at a certain

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Speaker 1: setting and say, you know, I'm really looking for metals

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Speaker 1: that fall within this range, yeah, perhaps gold. I've actually

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Speaker 1: seen uh, metal detector booths and they'll have like this

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Speaker 1: giant jar of class rings that people have lost, which

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Speaker 1: is sort of a you know reminder that you know, hey,

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Speaker 1: you you can find stuff if you just take your

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Speaker 1: metal to of course, people look at you funny, but yeah,

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Speaker 1: that way. That way. Let's say that you're out there

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Speaker 1: looking for something specific. You can you know, meld detectors

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Speaker 1: have settings where you can, uh you can tell the

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Speaker 1: meld detector to ignore anything outside of a particular range

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Speaker 1: of frequencies. So in other words, you're saying, you might say,

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Speaker 1: I'm only interested in finding silver. Let's say, so what

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Speaker 1: I'll do is I'll set my meld detector so that

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Speaker 1: it'll it'll only uh activate, it will only alert me

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Speaker 1: if something that generates a magnetic frequency similar to that

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Speaker 1: of silver is encountered by the metal detector. So in

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Speaker 1: other words, what you might you might pass over a

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Speaker 1: gold deposit and nothing happens. But as soon as you

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Speaker 1: go over that that silver half dollar but ink, and

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Speaker 1: then you dig it up and you like, hey, look

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Speaker 1: I'm rich. I Meanwhile, the gold guy behind you was like, sucker.

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Speaker 1: Well that's that. That can be called notching. Basically, you

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Speaker 1: set it for a if you imagine a scale, uh

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Speaker 1: you know, he's one notch on that scale. Or some

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Speaker 1: of the more sophisticated metal detectors will allow you to

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Speaker 1: set more than one notch r So that way you

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Speaker 1: could look for both silver on gold and you'd say,

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Speaker 1: ha ha, Mr smarty gold pants. Um, now that's that's

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Speaker 1: the VLF. The post induction metal detector a little bit different. Yeah,

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Speaker 1: it uses only a single coil, or it can use

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Speaker 1: multiple coils working at the same time. Yeah, but they're

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Speaker 1: these are these are coils that haven't that don't have

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Speaker 1: that shielding. It's not like you have a transmitter coil

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Speaker 1: and then a receiver coil, and all of these coils

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Speaker 1: are generating very quick bursts of electricity, which of course

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Speaker 1: creates a very sharp magnetic wave. And uh so it's

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Speaker 1: just a really quick spike and then what will happen

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Speaker 1: is that magnetic wave if it encounters a metal object again,

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Speaker 1: that metal object will have to will generate its own

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Speaker 1: magnetic wave, and the metal detector will pick up on that.

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Speaker 1: And it's all it's kind of like an echo, right,

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Speaker 1: It's kind of like an echo, right, thank you. So

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Speaker 1: if you think about it that way, it's it's like

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Speaker 1: sending out a signal and waiting for something to bounce back. Yeah,

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Speaker 1: but it's very fast. I mean the average is about

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Speaker 1: a hundred pulses per second, which is yeah, fairly rapid,

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Speaker 1: pretty quick, and then you're looking for the reflected pulse. Yes,

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Speaker 1: which is what the the object that is under the

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Speaker 1: ground or wherever. Uh, that's the the the pulse that

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Speaker 1: it generates in response to the one that came from

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Speaker 1: the MEL detector. Yeah. Now it uses a these these

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Speaker 1: types of metal detectors use a sampling circuit basically trying

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Speaker 1: to determine whether it's actually metal that you're finding or

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Speaker 1: something else, some other type of magnetic field that is

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Speaker 1: interfering with this signal. And it's basically judging that based

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Speaker 1: on the amount of time it takes, uh too to reflect. Um. Yeah,

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Speaker 1: that's another thing that we should point out is that

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Speaker 1: MEL detectors can and encounter lots of different kinds of interference.

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Speaker 1: Not just the composition of the soil. But let's say

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Speaker 1: that you happen to cross over where in elector called

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Speaker 1: cable has been buried. That could cause a problem. Your

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Speaker 1: metal detector might think that, hey, look there's gold in

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Speaker 1: them our hills, and truth, what you've hit is the

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Speaker 1: power line, which you don't want to dig that up. No,

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Speaker 1: it could result in everything from death, which is in

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Speaker 1: the metal detection biz we call a bad thing, or

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Speaker 1: it could result in or and or it could result

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Speaker 1: in an entire region losing electricity. That's also a bad thing.

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Speaker 1: That's that's a very good point. I mean, these these

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Speaker 1: metal detectures are not only incredibly useful, they can be

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Speaker 1: a lot of fun. A lot of hobbyists love them.

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Speaker 1: But you do have to be very very careful. Um,

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Speaker 1: and it's good to know your the territory. To quote

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Speaker 1: a certain musical, but yeah, I mean, you need to

332
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Speaker 1: know the territory. You gotta know where you're you're digging

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Speaker 1: because you you really could get hurt. Hey, guys, it's

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Speaker 1: Jonathan from the present day, butting in here. I was

335
00:20:00,160 --> 00:20:02,320
Speaker 1: to want to talk to you for a second because

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00:20:02,840 --> 00:20:06,280
Speaker 1: my my, my AD detector is going off. Looks like

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00:20:06,320 --> 00:20:17,200
Speaker 1: we've got a sponsor read So we have an integrator

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00:20:17,920 --> 00:20:22,320
Speaker 1: on these on these pulse induction metal detectives, and that's

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00:20:22,400 --> 00:20:25,480
Speaker 1: reading the signals from the sampling circuit and converting them

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00:20:25,480 --> 00:20:28,639
Speaker 1: to d C. That's not current, yeah, not the district

341
00:20:28,640 --> 00:20:31,840
Speaker 1: of Columbia. Yeah, not not a comic book publisher either.

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00:20:32,080 --> 00:20:34,919
Speaker 1: And that's feeding into the audio circuit and that is

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Speaker 1: what beats. Yeah, that's the stuff what beats. The pulse indicator.

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Speaker 1: The thing is, uh, these are very good at detecting metal,

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00:20:42,480 --> 00:20:45,159
Speaker 1: but they're not very good at discriminating between different types

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Speaker 1: of metal. UM. So you're not going to get the

347
00:20:49,520 --> 00:20:52,320
Speaker 1: level of precision that you would get with a VLF

348
00:20:53,080 --> 00:20:56,600
Speaker 1: metal detector. But you know, they also you've got to

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Speaker 1: remember that these different types of detectors, while some of

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00:20:59,280 --> 00:21:02,080
Speaker 1: them may work in conditions that others do not, there's

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00:21:02,160 --> 00:21:06,800
Speaker 1: there's also a price range here as well. Oh yes, yes, now, yeah,

352
00:21:06,800 --> 00:21:12,240
Speaker 1: the beat frequency oscillator metal detectors can be uh fairly affordable. UM.

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00:21:12,359 --> 00:21:14,960
Speaker 1: They also used two coils, but one is in the

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00:21:15,000 --> 00:21:17,000
Speaker 1: search head and the other one is actually in the

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00:21:17,000 --> 00:21:20,720
Speaker 1: control box. UM. They're connected to an oscillator that as

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00:21:21,720 --> 00:21:26,359
Speaker 1: pulsing UM many many times per second, thousands of times

357
00:21:26,359 --> 00:21:30,080
Speaker 1: per second UM. And and the and the frequency of

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00:21:30,160 --> 00:21:32,480
Speaker 1: the one that's inside the control box and the one

359
00:21:32,520 --> 00:21:36,880
Speaker 1: that's inside the actual detector are slightly offset. They're not

360
00:21:37,080 --> 00:21:42,360
Speaker 1: in sync or backstreet voice. Oh you got the other

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00:21:42,359 --> 00:21:48,960
Speaker 1: one I was gonna do so yeah, well, ironically enough

362
00:21:49,000 --> 00:21:52,800
Speaker 1: to our our current part of the conversation. They create

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00:21:52,920 --> 00:21:55,679
Speaker 1: radio waves UM, and then the receiver in the control

364
00:21:55,720 --> 00:22:00,199
Speaker 1: box UH picks that up and plays tones to you

365
00:22:00,280 --> 00:22:03,760
Speaker 1: know when you're you're coming into range of metal, right,

366
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Speaker 1: because what's happening is that when the metal encounters this

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00:22:08,600 --> 00:22:12,959
Speaker 1: uh this this this electromagnetic field that is going to

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00:22:13,000 --> 00:22:17,040
Speaker 1: alter that radio wave. And so what's really listening for

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00:22:17,080 --> 00:22:20,600
Speaker 1: our changes in the sound that you're hearing. The change

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Speaker 1: in the sound indicates that you have encountered something that

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00:22:24,440 --> 00:22:27,840
Speaker 1: is generating this magnetic field. Because of the one you're generating,

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00:22:28,119 --> 00:22:32,200
Speaker 1: they know what they're going through. Um. So yeah, I

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Speaker 1: mean detectors killed the radio star. But these these uh,

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00:22:36,760 --> 00:22:40,160
Speaker 1: like I said, these are a lot cheaper to manufacture.

375
00:22:40,200 --> 00:22:43,679
Speaker 1: And therefore, if you are uh interested in getting your

376
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Speaker 1: feet wet uh in the metal detector, the thing is

377
00:22:47,600 --> 00:22:49,880
Speaker 1: a hobby, you might consider this, but they're they're far

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00:22:49,960 --> 00:22:53,080
Speaker 1: less accurate as in terms of being able to give

379
00:22:53,119 --> 00:22:58,240
Speaker 1: you any kind of discrimination or any really any real control. Um,

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00:22:58,760 --> 00:23:01,680
Speaker 1: they actually use these are the types of metal detectors

381
00:23:01,720 --> 00:23:05,800
Speaker 1: that you the handheld detectors that they use the airport. Um,

382
00:23:05,840 --> 00:23:08,280
Speaker 1: you know if you walk through the scanner and and

383
00:23:08,280 --> 00:23:09,840
Speaker 1: then yeah, that's the type they use in the one.

384
00:23:09,880 --> 00:23:13,359
Speaker 1: Because they don't really need to know whether it's gold

385
00:23:13,480 --> 00:23:15,800
Speaker 1: or iron. They just want to know what it is

386
00:23:15,840 --> 00:23:18,479
Speaker 1: that you've got now once once, once something beeps, then

387
00:23:18,520 --> 00:23:20,800
Speaker 1: they can say, all right, well let's see what that is.

388
00:23:20,960 --> 00:23:24,400
Speaker 1: They don't, you know, necessarily need to know immediately. Yeah.

389
00:23:24,440 --> 00:23:27,960
Speaker 1: And the metal detectors, the frames at the airport, they

390
00:23:28,119 --> 00:23:30,960
Speaker 1: work on essentially the same principles we've talked about here.

391
00:23:31,400 --> 00:23:34,360
Speaker 1: They're generating electromagnetic fields, which of course has brought up

392
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Speaker 1: some concerns with people who may have uh devices like

393
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Speaker 1: medical devices that could react to electromagnetic fields. That's why

394
00:23:42,720 --> 00:23:46,320
Speaker 1: you'll occasionally hear about UH folks like that having to

395
00:23:46,440 --> 00:23:50,080
Speaker 1: go through like a pat down security as opposed to

396
00:23:50,240 --> 00:23:52,600
Speaker 1: a metal detector, just because of the concern that it

397
00:23:52,680 --> 00:23:56,720
Speaker 1: could interfere with a medical device. Right right now, with

398
00:23:56,960 --> 00:23:59,960
Speaker 1: with all of these um, what you're gonna find depends

399
00:24:00,200 --> 00:24:03,320
Speaker 1: on the type of metal detector, the type of metal

400
00:24:03,440 --> 00:24:06,440
Speaker 1: that you're looking for, about how big it is, the

401
00:24:06,520 --> 00:24:09,320
Speaker 1: kind of makeup of the soil, um any kind of

402
00:24:09,359 --> 00:24:13,520
Speaker 1: interference from other objects, and the halo, which is basically

403
00:24:14,040 --> 00:24:16,439
Speaker 1: you know, if you have a piece of metal in

404
00:24:16,480 --> 00:24:19,800
Speaker 1: the soil, it's going to read a little bit differently,

405
00:24:19,800 --> 00:24:22,199
Speaker 1: it's going to it's going to register is larger than

406
00:24:22,240 --> 00:24:25,600
Speaker 1: it actually is. Yeah, it's it's because those interesting things. Yeah,

407
00:24:25,640 --> 00:24:28,480
Speaker 1: they I could see your halo. I was I was waiting.

408
00:24:28,520 --> 00:24:31,840
Speaker 1: I was trying so hard not to go into that.

409
00:24:32,200 --> 00:24:36,200
Speaker 1: We've done so many songs references in this podcast. It's crazy.

410
00:24:36,400 --> 00:24:40,119
Speaker 1: This might be our like our most intense the funny

411
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Speaker 1: thing references per minute other than the first one. None

412
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Speaker 1: of them have been metal. That's true, that's true. So

413
00:24:47,480 --> 00:24:49,719
Speaker 1: but yeah, no, that this is really the halo effect

414
00:24:49,760 --> 00:24:52,080
Speaker 1: is really an interesting thing. It's just this the fact

415
00:24:52,080 --> 00:24:57,520
Speaker 1: that certain kinds of metal objects, uh, can actually increase

416
00:24:57,600 --> 00:25:00,439
Speaker 1: the conductivity of the soil that's around on them. And

417
00:25:00,520 --> 00:25:03,560
Speaker 1: the longer that object, those particular objects have been in

418
00:25:03,600 --> 00:25:07,600
Speaker 1: the ground, the greater that conductivity change can be. So

419
00:25:07,640 --> 00:25:10,120
Speaker 1: then yeah, you might be like, hey, there's a there's

420
00:25:10,119 --> 00:25:13,439
Speaker 1: a Sherman tank down there or something, and it just

421
00:25:13,480 --> 00:25:15,760
Speaker 1: turns out that there's another object that's been down there

422
00:25:15,800 --> 00:25:18,720
Speaker 1: and has affected the conductivity of the soil. But it's

423
00:25:18,720 --> 00:25:21,359
Speaker 1: pretty phenomenal. If you have a Sherman tank buried in

424
00:25:21,359 --> 00:25:23,720
Speaker 1: your backyard, please give me a call. I'm I'm interested

425
00:25:23,760 --> 00:25:27,479
Speaker 1: to well not anymore. Yeah, I mean, well, you think

426
00:25:27,520 --> 00:25:29,520
Speaker 1: about it, it it makes sense. If you have let's say,

427
00:25:29,600 --> 00:25:32,560
Speaker 1: let's say the aforementioned screw and it's been there for

428
00:25:32,600 --> 00:25:36,160
Speaker 1: a couple of years, it's let's say iron and it's

429
00:25:36,200 --> 00:25:39,840
Speaker 1: beginning to rust, it's beginning to disintegrate, and you can

430
00:25:39,920 --> 00:25:42,920
Speaker 1: change the conduct conductivity depending on the Again, it also

431
00:25:42,960 --> 00:25:46,639
Speaker 1: depends rain, and you know, it really depends upon the

432
00:25:46,640 --> 00:25:49,520
Speaker 1: composition of the soil itself as well. So, yeah, if

433
00:25:49,520 --> 00:25:52,080
Speaker 1: there's a lot of iron content in the soil, that's

434
00:25:52,119 --> 00:25:55,240
Speaker 1: gonna cause some issues when you're when you're doing mild section,

435
00:25:55,280 --> 00:25:57,000
Speaker 1: you know, you're just you're gonna get a lot of

436
00:25:57,040 --> 00:25:59,720
Speaker 1: interference and you just have to factor that in. Doesn't

437
00:25:59,760 --> 00:26:01,560
Speaker 1: mean that the metal detector is going to be useless.

438
00:26:01,560 --> 00:26:04,080
Speaker 1: It just means that you have to kind of adjust

439
00:26:04,200 --> 00:26:08,800
Speaker 1: your expectations and listen for bigger changes in UH in

440
00:26:08,880 --> 00:26:11,800
Speaker 1: the soil content UH and not and kind of kind

441
00:26:11,800 --> 00:26:15,840
Speaker 1: of ignore the noise, separate the signal from the noise. Yeah,

442
00:26:15,920 --> 00:26:19,879
Speaker 1: I would argue that it probably takes some personal discrimination too.

443
00:26:19,960 --> 00:26:21,919
Speaker 1: You really need to get out there in practice if

444
00:26:21,960 --> 00:26:24,840
Speaker 1: you're going to start using doing metal detecting as a hobby,

445
00:26:25,520 --> 00:26:28,000
Speaker 1: UM and maybe even trying it with things that you

446
00:26:28,080 --> 00:26:30,960
Speaker 1: would that you know what they are. You know, some coins,

447
00:26:31,680 --> 00:26:36,200
Speaker 1: a ring, a screw driver, you know something that you hammer, hammers,

448
00:26:36,359 --> 00:26:39,240
Speaker 1: you know, sherman tanks, Uh, stuff that you do just

449
00:26:39,560 --> 00:26:42,320
Speaker 1: you know, tend to run across in your general area. Well,

450
00:26:42,359 --> 00:26:43,960
Speaker 1: you know, you never know what you're gonna find when

451
00:26:43,960 --> 00:26:46,400
Speaker 1: you're out in a field somewhere, and if you can

452
00:26:46,160 --> 00:26:49,479
Speaker 1: identify what they are, you can get a sense of

453
00:26:49,520 --> 00:26:52,320
Speaker 1: what different metals sound like. How get a feel for

454
00:26:52,359 --> 00:26:55,399
Speaker 1: how your metal detector works, how sensitive it is, and

455
00:26:55,400 --> 00:26:58,639
Speaker 1: how sensitive it is. Um, Yeah, it can be a

456
00:26:58,680 --> 00:27:01,040
Speaker 1: lot of fun to uh you were talking about before,

457
00:27:01,200 --> 00:27:05,640
Speaker 1: like going to uh battlefields course, I imagine probably all

458
00:27:05,680 --> 00:27:09,080
Speaker 1: the major battlefields have been picked pretty clean at this point,

459
00:27:09,119 --> 00:27:12,199
Speaker 1: you would think. But it's it's amazing what you can

460
00:27:12,240 --> 00:27:15,320
Speaker 1: stumble across. It's again, it's one of those things where

461
00:27:15,320 --> 00:27:19,160
Speaker 1: it may be it may require a phenomenal amount of luck,

462
00:27:19,800 --> 00:27:23,320
Speaker 1: sure experience, there's no such thing as luck, but it

463
00:27:23,359 --> 00:27:26,760
Speaker 1: may require a phenomenal a series of coincidences in order

464
00:27:26,760 --> 00:27:28,960
Speaker 1: for you to stumble across the right section to find

465
00:27:28,960 --> 00:27:33,600
Speaker 1: something significant. But really you never know. You just it's

466
00:27:33,680 --> 00:27:36,880
Speaker 1: it's amazing to me how something that you would think, oh, well,

467
00:27:36,880 --> 00:27:39,320
Speaker 1: this has got so much traffic. There's no way there's

468
00:27:39,400 --> 00:27:41,960
Speaker 1: anything of significance can be found there. And yet like

469
00:27:42,080 --> 00:27:45,639
Speaker 1: five years later you'll find that the find of the injury.

470
00:27:45,920 --> 00:27:49,919
Speaker 1: How did that happen? Yeah, and you don't know what's

471
00:27:49,960 --> 00:27:54,080
Speaker 1: around in places that you know might be a value.

472
00:27:54,119 --> 00:27:57,399
Speaker 1: I mean again, people find I'm still searching for black beards, treasure,

473
00:27:57,520 --> 00:27:59,800
Speaker 1: all kinds of stuff out in time. I go to

474
00:27:59,840 --> 00:28:04,440
Speaker 1: the airlinas out in normal places. Maybe you should actually

475
00:28:04,520 --> 00:28:07,840
Speaker 1: go to the everyday beach instead of Finland. That's probably

476
00:28:07,840 --> 00:28:11,800
Speaker 1: part of the problem. Yeah, you know, Charleston is so nice.

477
00:28:11,840 --> 00:28:14,960
Speaker 1: I just like to know, spend some time there enough. Yeah,

478
00:28:15,240 --> 00:28:19,320
Speaker 1: people even use them for prospecting, you know, and uh

479
00:28:19,359 --> 00:28:21,560
Speaker 1: and for coin shooting. Now, if you do want to

480
00:28:21,640 --> 00:28:24,080
Speaker 1: use your mail detective for prospecting, there are some things

481
00:28:24,119 --> 00:28:28,440
Speaker 1: you need to remember. First, you have to grow a

482
00:28:28,560 --> 00:28:30,840
Speaker 1: bear of at least a foot in length that needs

483
00:28:30,880 --> 00:28:34,399
Speaker 1: to be gray and grizzly. He's gonne punchy, ladies and gentlemen. Second,

484
00:28:34,440 --> 00:28:36,399
Speaker 1: you need to be able to say things like consarn

485
00:28:36,520 --> 00:28:39,160
Speaker 1: it with a straight face. And then third, the most

486
00:28:39,200 --> 00:28:41,080
Speaker 1: important thing about being a prospector is you have to

487
00:28:41,120 --> 00:28:43,680
Speaker 1: develop your crazy prospect or dance when you strike gold.

488
00:28:44,720 --> 00:28:49,280
Speaker 1: Very important. Yeah, coin shooting is the practice of looking

489
00:28:49,320 --> 00:28:53,400
Speaker 1: for coins after an outdoor event like a wedding or

490
00:28:53,520 --> 00:28:56,520
Speaker 1: or like stock you go to you go to some

491
00:28:56,560 --> 00:29:00,240
Speaker 1: big outdoor conference and you take a mail to actor

492
00:29:00,240 --> 00:29:03,120
Speaker 1: and you start looking for change. The thing is that

493
00:29:03,120 --> 00:29:04,640
Speaker 1: if you live in an area where this sort of

494
00:29:04,640 --> 00:29:07,720
Speaker 1: stuff goes on in a regular basis, you could presumably

495
00:29:07,840 --> 00:29:11,440
Speaker 1: pay off that mail detector after you know, a few

496
00:29:11,840 --> 00:29:16,240
Speaker 1: visits to these these areas, once the concert is over

497
00:29:16,800 --> 00:29:20,080
Speaker 1: or a game or whatever. Um, you know. And and

498
00:29:20,160 --> 00:29:24,200
Speaker 1: because we're usually talking about change, you know, some some

499
00:29:24,320 --> 00:29:27,760
Speaker 1: nickels or dimes or quarters or whatever. But whatever money

500
00:29:27,840 --> 00:29:29,960
Speaker 1: you use, because you know, it's not all just United

501
00:29:30,000 --> 00:29:34,440
Speaker 1: States folks. Well, if you find euros, you're rich, because

502
00:29:34,480 --> 00:29:37,320
Speaker 1: I think a euro is equivalent to like seventeen dollars

503
00:29:37,360 --> 00:29:41,800
Speaker 1: at this point. Um, that's a gross exaggeration, but the

504
00:29:41,800 --> 00:29:45,520
Speaker 1: point being that, you know, yeah, you could conceivably pay

505
00:29:45,560 --> 00:29:50,360
Speaker 1: off your mail detect there's costs after a few visits,

506
00:29:50,520 --> 00:29:53,840
Speaker 1: you know. Um. But although a lot of people just

507
00:29:53,960 --> 00:29:56,320
Speaker 1: enjoy the this as a hobby, like it's just it's

508
00:29:56,320 --> 00:29:59,880
Speaker 1: a way to get outside. You're enjoying your joining time

509
00:30:00,000 --> 00:30:03,200
Speaker 1: outdoors and you're finding stuff which just brings you a

510
00:30:03,320 --> 00:30:07,440
Speaker 1: level of of of satisfaction, right at least that whole

511
00:30:07,480 --> 00:30:10,760
Speaker 1: treasure hunting aspect. You know when I when we discover something,

512
00:30:10,760 --> 00:30:13,040
Speaker 1: there's an element of satisfaction there that you can't put

513
00:30:13,040 --> 00:30:17,440
Speaker 1: a monetary value on. Who Yeah, yeah, you're just like, hey,

514
00:30:17,480 --> 00:30:21,200
Speaker 1: look I found some money woo, And yeah, there's there's

515
00:30:21,200 --> 00:30:24,320
Speaker 1: an enjoyment level there that goes beyond oh and it's

516
00:30:24,360 --> 00:30:28,560
Speaker 1: worth you know, seventy five cents um, although the five

517
00:30:28,560 --> 00:30:31,360
Speaker 1: cents always nice to have seventy five cents more than

518
00:30:31,400 --> 00:30:33,240
Speaker 1: you had, but when you showed up at the field.

519
00:30:33,560 --> 00:30:38,440
Speaker 1: So yeah, I keep wondering, actually, why the value of

520
00:30:38,480 --> 00:30:42,440
Speaker 1: the giant jar of class rings. You'd figure they'd cash

521
00:30:42,480 --> 00:30:44,880
Speaker 1: that in, Yeah, I mean for more than just selling

522
00:30:44,880 --> 00:30:47,920
Speaker 1: metal detectors. Maybe that's more lucrative than selling off some

523
00:30:47,960 --> 00:30:49,840
Speaker 1: of those classroom you have, prying out all the little

524
00:30:49,920 --> 00:30:53,200
Speaker 1: jewels and melting that stuff down and then just hey,

525
00:30:53,200 --> 00:30:55,200
Speaker 1: you know you can yourself bar a gold. It's worth

526
00:30:55,200 --> 00:30:57,800
Speaker 1: its weight in gold. All right, guys, hope you enjoyed

527
00:30:57,840 --> 00:31:00,280
Speaker 1: that classic episode of tech Stuff How Metal detect there's

528
00:31:00,320 --> 00:31:02,800
Speaker 1: work if you would like to contact the show. Maybe

529
00:31:02,800 --> 00:31:06,400
Speaker 1: you've got a topic in mind, maybe you've got some

530
00:31:06,480 --> 00:31:10,360
Speaker 1: questions or concerns, maybe you just want to say, hey, Jonathan,

531
00:31:10,640 --> 00:31:13,680
Speaker 1: you're doing a nice job. Well, go to our website

532
00:31:13,800 --> 00:31:17,160
Speaker 1: that's tech stuff podcast dot com. There you're gonna find

533
00:31:17,240 --> 00:31:20,760
Speaker 1: all the different ways you can contact me or the show.

534
00:31:21,240 --> 00:31:24,800
Speaker 1: You also find links to our merchandise store. And remember

535
00:31:24,840 --> 00:31:27,360
Speaker 1: every purchase you make goes to help the show and

536
00:31:27,640 --> 00:31:29,840
Speaker 1: more so, go check that out. We're really proud of it.

537
00:31:29,880 --> 00:31:33,200
Speaker 1: Tor has been working hard on that website for a while,

538
00:31:33,280 --> 00:31:35,680
Speaker 1: so I know she's very excited that you guys are

539
00:31:35,720 --> 00:31:38,040
Speaker 1: gonna get a chance to interact on it. She's just

540
00:31:38,080 --> 00:31:43,080
Speaker 1: given me a big smile. She's dancing. Look at her,

541
00:31:43,120 --> 00:31:49,040
Speaker 1: go gosh, sorry, wow, she just did the floss. Now

542
00:31:49,080 --> 00:31:53,320
Speaker 1: she's doing the hand give. It's amazing. Thanks Torry. Well, guys,

543
00:31:53,360 --> 00:31:56,040
Speaker 1: that's all for me. I'll talk to you again really

544
00:31:56,080 --> 00:32:04,240
Speaker 1: soon for more on this and thousands of other topics.

545
00:32:04,520 --> 00:32:15,760
Speaker 1: Is it how stuff works dot com