WEBVTT - Rerun: How Metal Detectors Work 0:00:04.240 --> 0:00:12.600 Get in touch with technology with tex stuff from Hey 0:00:12.640 --> 0:00:14.920 there everyone, and welcome to tech stuff. This is Jonathan 0:00:14.960 --> 0:00:19.159 Strickland with another classic episode. Don't worry, We're gonna have 0:00:19.239 --> 0:00:21.920 new ones really soon, but this one is a pretty 0:00:21.960 --> 0:00:23.800 cool one. It's one that I really enjoyed doing with 0:00:23.880 --> 0:00:27.840 Chris Paillette several years ago. It's all about metal detectives, 0:00:27.840 --> 0:00:33.960 how they were today we are going to talk about. 0:00:34.640 --> 0:00:37.120 You know what, this was a topic that I don't 0:00:37.159 --> 0:00:40.080 know that anyone has ever requested. Um. It came to 0:00:40.120 --> 0:00:44.040 me actually as I was looking through stuff in my 0:00:44.040 --> 0:00:47.920 basement and went metal detectors. We should talk about We've 0:00:47.920 --> 0:00:50.720 never talked about metal detective Actually, we've sort of talked 0:00:50.720 --> 0:00:54.040 about metal detectors because metal detectors use a lot of 0:00:54.080 --> 0:00:58.080 the technology we talked about before, especially the relationship of 0:00:58.360 --> 0:01:02.480 magnetism to atricity. Yeah. Um, but yeah, I mean it's 0:01:02.520 --> 0:01:06.120 something that we run into very often, especially if we 0:01:06.160 --> 0:01:08.520 travel and walk through the metal detectors at the airport 0:01:08.840 --> 0:01:12.080 if we're not getting back scattered or you know, dropping 0:01:12.120 --> 0:01:14.800 stuff that you can't find, losing your wedding ring and 0:01:14.959 --> 0:01:19.280 the maltch outside. Yikes, that's good stuff. I've done that 0:01:20.280 --> 0:01:22.440 I still have it, So there you go. I've never 0:01:22.480 --> 0:01:27.000 lost my wedding ring. Alright, well it was only temporary. 0:01:27.640 --> 0:01:31.000 So anyway, metal detectors talk about what they are. We're 0:01:31.040 --> 0:01:34.039 mostly going to be talking about the kind that you 0:01:34.040 --> 0:01:37.400 would you would carry with you, you know, the portable 0:01:37.400 --> 0:01:40.640 metal detectors that you would use when looking for say, 0:01:40.680 --> 0:01:44.320 loose change on the beach, or you know, searching for 0:01:44.400 --> 0:01:50.280 that rare civil war uh bullet or a gun that 0:01:50.480 --> 0:01:52.560 might be part of you know, in an area that 0:01:52.600 --> 0:01:55.120 you knew the battle happened here, so there may very 0:01:55.200 --> 0:01:58.160 well be stuff here. Yeah, we should definitely talk about 0:01:58.200 --> 0:02:00.920 some of the applications of the technology GUM. And I 0:02:01.160 --> 0:02:02.960 would like to point out that we have an excellent 0:02:03.040 --> 0:02:05.080 article on how stuff Works dot com if you're interested 0:02:05.120 --> 0:02:09.760 in learning more. Um it's called how Metal Detectors Work. Yeah. 0:02:09.760 --> 0:02:11.760 It should be pretty easy for people to find, written 0:02:11.800 --> 0:02:15.440 by Jeff Tyson, and it is a very good article 0:02:15.600 --> 0:02:20.080 and very uh simple to follow, easy to understand. I 0:02:20.080 --> 0:02:22.519 would say this is this is one of those really 0:02:22.639 --> 0:02:26.040 great how stuff works articles. By the time you get 0:02:26.080 --> 0:02:28.400 through it and you're like, oh, yeah, no, that totally 0:02:28.480 --> 0:02:31.359 makes sense, especially if you have a little bit of 0:02:31.400 --> 0:02:37.560 grounding in the way electromagnetism works and conductors and inducers. 0:02:38.600 --> 0:02:41.480 So we'll we'll cover that. I mean, we've talked about 0:02:41.480 --> 0:02:44.120 an in previous podcast, but we'll we'll do a quick 0:02:44.160 --> 0:02:47.880 brush up so that we can explain it. So you wanna, 0:02:48.080 --> 0:02:50.639 let's let's talk about the the Jeff does a great 0:02:50.720 --> 0:02:55.120 job at breaking down what the typical portable metal detector, 0:02:55.200 --> 0:02:58.679 the four main parts of one, what they would be. Yeah, 0:02:58.680 --> 0:03:01.400 I mean, if you've ever seen people walking around with 0:03:01.880 --> 0:03:03.840 a metal detector, you you sort of know what they 0:03:03.880 --> 0:03:07.000 look like. They have a round dish part that's used 0:03:07.080 --> 0:03:11.839 close to the ground. That's a that's called the coil. Then, yes, 0:03:11.919 --> 0:03:16.040 and then you have the stabilizer um, which is the 0:03:16.080 --> 0:03:18.640 part that you actually hold onto, that holds onto your 0:03:18.919 --> 0:03:21.400 that that you see under your arm, because you know, frankly, 0:03:22.120 --> 0:03:24.960 having used a metal detector, it's not the lightest thing, right. 0:03:25.520 --> 0:03:28.400 This This helps, This helps distribute the weight somewhat so 0:03:28.480 --> 0:03:31.160 that you're not you don't feel like you're carrying around 0:03:31.200 --> 0:03:34.920 a you know, ten pound brick the whole time, because 0:03:34.960 --> 0:03:38.600 without that then you would get very tired very quickly. Yeah, 0:03:38.680 --> 0:03:41.040 And the the ten pound the aforementioned ten pound brick, 0:03:41.080 --> 0:03:43.600 which probably isn't ten pounds, but it certainly can feel 0:03:43.600 --> 0:03:46.640 that way after a while. That's the control box, uh, 0:03:46.640 --> 0:03:49.640 and you've got all your your electronics in there. And 0:03:49.640 --> 0:03:55.960 and then then yes, the long skinny part that's the shaft. Yes, 0:03:56.040 --> 0:03:58.800 it connects the coil at the base to the part 0:03:58.880 --> 0:04:01.280 that you're holding, and the of course the control box. 0:04:01.600 --> 0:04:04.240 So those are your four basic parts of your basic 0:04:04.440 --> 0:04:07.840 metal detector. Yes. And then you know you have your headphones, 0:04:08.040 --> 0:04:11.120 because this is one of our episodes of stuff that 0:04:11.240 --> 0:04:14.280 beeps and stuff what beat stuff? What beeps and it 0:04:14.360 --> 0:04:17.400 it does in fact beep. Yeah, there's usually some sort 0:04:17.400 --> 0:04:22.920 of audible alert that you have in fact detected metal. Yeah. Now, 0:04:23.120 --> 0:04:26.320 more sophisticated uh, metal detectors will tell you a lot 0:04:26.360 --> 0:04:29.680 more often with uh, well sometimes with with an audible tone, 0:04:29.720 --> 0:04:33.520 but also with a visual uh, some kind of visual analysis. 0:04:33.880 --> 0:04:36.120 We can get into that too in a minute. So 0:04:36.560 --> 0:04:40.880 there are three main types of metal detectors, the ones 0:04:40.920 --> 0:04:46.440 at work, the three three main approaches to to metal detection. 0:04:46.640 --> 0:04:50.440 Let's say, uh, there's, um, there's the very low frequency, 0:04:50.520 --> 0:04:54.520 which is probably the most the most popular or the 0:04:54.560 --> 0:04:56.840 most common type of mel detector, at least for the 0:04:57.160 --> 0:05:01.040 portable metal detectors. Um. Yeah, they When we get into this, 0:05:01.120 --> 0:05:03.400 you'll you'll see that each of these different types has 0:05:03.440 --> 0:05:06.560 its own strengths and weaknesses. And you might say, well, 0:05:06.640 --> 0:05:09.799 the VLF detector sounds great, why would you use the others? 0:05:10.000 --> 0:05:12.960 We'll get into that. Yeah. The other two are pulse 0:05:13.080 --> 0:05:18.560 induction and beat frequency oscillation. Yeah. I knew a beat 0:05:18.640 --> 0:05:26.160 frequency oscillator once. He was awesome. Yeah, Anyway, something else. 0:05:26.200 --> 0:05:31.280 I guess that's the beat boxer frequency oscillator. That the uh, 0:05:31.440 --> 0:05:34.240 the VLF metal detector is the type that I have, 0:05:35.160 --> 0:05:41.320 UM and Uh. The the basic differences uh, and these 0:05:41.480 --> 0:05:45.479 is you'll see those really in the coils, to be honest, 0:05:45.960 --> 0:05:51.640 because the VLF has two different coils. One transmits UM 0:05:51.800 --> 0:05:54.480 and and the other is basically an antenna to pick 0:05:54.600 --> 0:05:57.160 up the signals, so they're shielded from one another so 0:05:57.240 --> 0:06:00.120 it doesn't pick up because otherwise you turned it on, 0:06:00.160 --> 0:06:02.360 you would just have the receiver saying, oh my gosh, 0:06:02.400 --> 0:06:07.200 there's metal everywhere. Holy crap, you're rich even up in 0:06:07.240 --> 0:06:10.920 the air. It's it's literally everywhere. Yeah, that would that 0:06:10.960 --> 0:06:13.359 would not be very useful. And taking this back to 0:06:13.440 --> 0:06:16.920 the store where it's a detector detector. This does not 0:06:17.000 --> 0:06:19.800 do me any good. It's a detect it's a detected 0:06:19.839 --> 0:06:27.320 at or where's perry. So the the the transmitter coil 0:06:27.839 --> 0:06:31.880 um it's it. Think of a circle, all right, It's 0:06:31.920 --> 0:06:35.960 a this circular part at the base of the metal detector. 0:06:36.480 --> 0:06:38.279 And if you were to take it apart, which I 0:06:38.320 --> 0:06:40.920 do not recommend you do, you would see that there 0:06:41.000 --> 0:06:44.279 is a pointer warranty and it may not work anymore. 0:06:44.600 --> 0:06:47.279 You will have a there's a coil of wire that 0:06:47.360 --> 0:06:50.560 goes around the perimeter of this circle like it's it's 0:06:50.560 --> 0:06:53.240 wrapped around. So the circle itself is let's say it's 0:06:53.240 --> 0:06:55.240 like a quarter of an inch thick, and you've got 0:06:55.240 --> 0:06:57.520 this coil of wire that's that's coiled around this quarter 0:06:57.520 --> 0:06:59.839 of an inch all the way around the perimeter of 0:06:59.839 --> 0:07:03.599 this circle. When you run electricity through this coil of wire, 0:07:04.279 --> 0:07:07.240 what happens besides the fact that electrons are moving through 0:07:08.000 --> 0:07:13.400 because of the nature of electricity and magnetism, well, when 0:07:13.440 --> 0:07:16.840 you run electricity around a coil like that, it generates 0:07:16.920 --> 0:07:20.480 a magnetic field. That's right, it does generate a magnetic field, 0:07:20.760 --> 0:07:24.080 and it generates a magnetic field perpendicular to the direction 0:07:24.120 --> 0:07:28.000 of the electricity. It's just the nature of electromagnetism. It's amazing, 0:07:28.280 --> 0:07:31.600 it's awesome. That's what how electro magnets work and UH, 0:07:32.000 --> 0:07:36.480 dynamo's work in UH and sort of using this in reverse. UM. 0:07:36.560 --> 0:07:40.120 So you've got electricity flowing through these coils and that 0:07:40.200 --> 0:07:43.880 generates the magnetic field. Well, it doesn't just the electricity. 0:07:43.880 --> 0:07:46.960 Electricity doesn't just flow in one direction, no, it it 0:07:47.240 --> 0:07:50.680 goes back and forth. It alternates very very very fast, 0:07:51.280 --> 0:07:53.440 almost as fast as I waffle back and forth on 0:07:53.440 --> 0:07:55.840 what I want to eat for lunch. And that means 0:07:55.920 --> 0:08:01.040 that the magnetic field also alternates. The the direction of 0:08:01.080 --> 0:08:04.640 the magnetic field changes. UH. And if you think of 0:08:04.680 --> 0:08:09.040 it in terms of the disc, the coil disc being 0:08:09.240 --> 0:08:11.240 towards the ground, you can think of it as the 0:08:11.280 --> 0:08:15.200 magnetic field occasionally is pushing against or pulling the ground 0:08:16.000 --> 0:08:17.840 in general. That just think of it that way. That's 0:08:17.840 --> 0:08:20.000 the direction of the magnetic field, while the electricity is 0:08:20.000 --> 0:08:22.280 going around and around in a circle, back and forth 0:08:22.360 --> 0:08:26.120 in in the various directions, and that alternation is happening 0:08:27.480 --> 0:08:31.880 hundreds of times per second. So you've got this magnetic field. 0:08:31.880 --> 0:08:35.640 That's that's just oscillating essentially right there against the ground. 0:08:36.440 --> 0:08:39.640 When it comes to contact with something that is metal, well, 0:08:39.679 --> 0:08:42.880 the metal will start to that magnetic field will cause 0:08:43.080 --> 0:08:48.000 a a weaker magnetic field to generate around the metal object. Yeah, 0:08:48.040 --> 0:08:52.360 basically induces a magnetic field in a metal object in 0:08:52.360 --> 0:08:55.720 the ground. So let's say, uh, um, you drop a 0:08:55.800 --> 0:09:00.600 screw and when you're trying to build something outside and 0:09:00.600 --> 0:09:02.480 you're trying to find it with your metal detector so 0:09:02.520 --> 0:09:04.080 that you don't step on it with a bare foot 0:09:04.120 --> 0:09:06.280 and you know, need a trip to the hospital and 0:09:06.320 --> 0:09:09.920 a tetennis shot. Um. So as soon as you run 0:09:10.080 --> 0:09:12.280 the coil of the field and you're not trying to 0:09:12.280 --> 0:09:14.200 touch the ground with it, you really just need it 0:09:14.440 --> 0:09:17.960 close to the ground. Um, it will find the screw. 0:09:18.240 --> 0:09:22.880 The screw will basically start inducing a It will metal 0:09:22.880 --> 0:09:26.440 detected detector will generate a field, and that will cause 0:09:26.520 --> 0:09:30.679 the screw to generate its own a weaker magnetic Oh yeah, yeah, 0:09:30.720 --> 0:09:33.920 considerably weaker, but it will the metal detector. Uh, the 0:09:33.960 --> 0:09:37.960 antenna coil inside the transmitter coil will say, oh, look 0:09:38.040 --> 0:09:40.760 there's something right there that is generating a magnetic field. 0:09:41.040 --> 0:09:45.160 It's right here. And the way that the antenna works 0:09:45.640 --> 0:09:48.640 is the way I was talking about with a dynamo. So, 0:09:48.679 --> 0:09:51.520 if you have a coil of wire and you introduce 0:09:51.600 --> 0:09:55.040 it into a fluctuating magnetic field, that will induce the 0:09:55.080 --> 0:09:58.920 flow of electricity within the wire. Right, just as electricity 0:09:58.960 --> 0:10:01.600 and the wire will create generated a magnetic field, a 0:10:01.600 --> 0:10:06.680 magnetic field will induce electricity to run through wire fluctuating 0:10:06.720 --> 0:10:09.200 magnetic field. It can't just be just a magnetic field. 0:10:09.800 --> 0:10:14.680 So when the weak magnetic field from the metal object 0:10:14.760 --> 0:10:19.640 hits that that the wire in the the the receiver 0:10:19.760 --> 0:10:25.560 coil that generates the electricity, which then alerts the control 0:10:25.600 --> 0:10:28.760 box that that's what When the control box gets an 0:10:28.760 --> 0:10:33.560 electric signal from the receiver coil, that says beep, something 0:10:33.640 --> 0:10:38.480 is here, stuff? What beeps? Yep? Stuff? What beeps? So yeah, 0:10:38.640 --> 0:10:44.240 that's the basic uh way that a VLF metal detector works. 0:10:44.280 --> 0:10:48.960 It shoots out this magnetic field. The polarization is alternating 0:10:49.400 --> 0:10:53.720 the same as the flow of electricity around the the 0:10:53.720 --> 0:10:57.240 the transmitter coil, and then the receiver coil picks up 0:10:57.320 --> 0:11:00.640 any magnetic fields generated by metal objec that are under 0:11:00.679 --> 0:11:04.080 the surface of the ground. It's pretty cool and generally 0:11:04.120 --> 0:11:07.960 it will go more or less about a foot. Yeah, 0:11:08.160 --> 0:11:10.760 you're not going to find you know, the Earth's core 0:11:12.559 --> 0:11:15.720 with a metal detect and the depth of what the 0:11:15.800 --> 0:11:19.440 depth of the The effectiveness of this metal detector is 0:11:19.480 --> 0:11:23.120 also going to be dependent on other factors, like the 0:11:23.240 --> 0:11:26.600 nature of the metal object itself, because some some metal 0:11:26.640 --> 0:11:29.680 objects are going to generate a stronger magnetic field than others, 0:11:29.760 --> 0:11:34.760 like iron. Uh. It will also depend on the composition 0:11:34.800 --> 0:11:37.360 of the soil. Yes, So the soil has a lot 0:11:37.559 --> 0:11:41.120 of elements in it that would create a magnetic field, 0:11:41.120 --> 0:11:43.520 You're gonna get a lot of interference, yeah, or or 0:11:43.559 --> 0:11:49.680 an environment where uh that that would conduct electricity more readily. 0:11:49.800 --> 0:11:51.720 Like if you were trying to look for something and 0:11:51.760 --> 0:11:55.679 say saltwater, you might have more difficulty than if you 0:11:55.720 --> 0:12:00.640 were looking, you know, on on a different type of soil. Um. Now, 0:12:00.679 --> 0:12:04.720 there is something to uh called phase shifting, Yes, And 0:12:04.760 --> 0:12:07.520 that's how it's able to tell what sort of metal, 0:12:07.679 --> 0:12:10.920 what sort of metal it is, UM. And it really 0:12:10.960 --> 0:12:14.000 has to do with the the inductance and the resistance 0:12:14.240 --> 0:12:17.040 of the object that you're looking for. Now, the inductance 0:12:17.120 --> 0:12:22.320 is um the objects ability to conduct electricity UM and 0:12:22.360 --> 0:12:24.840 if it's inductive, it will be able to to conduct 0:12:24.880 --> 0:12:29.679 electricity easily, but it's slow to react to changes in 0:12:29.720 --> 0:12:33.400 the electrical current. UM. If it's resistive, it doesn't conduct 0:12:33.480 --> 0:12:36.000 electricity is easily, but it is quick to react to 0:12:36.040 --> 0:12:39.719 those those changes. And a sophisticated metal detector will be 0:12:39.760 --> 0:12:43.280 able to tell you, well, that's I think that's gold, 0:12:43.400 --> 0:12:46.199 or I think that's high based upon that phase shift. 0:12:46.280 --> 0:12:48.679 Because the phace scheft for a particular element is going 0:12:48.720 --> 0:12:52.360 to remain constant, you know. That's that's why if it 0:12:52.400 --> 0:12:55.319 didn't remain constant, then this wouldn't matter at all, because 0:12:55.320 --> 0:12:57.520 it wouldn't you know, we wouldn't know. You know, It's 0:12:57.559 --> 0:12:59.679 like we just know something is down there, we wouldn't 0:12:59.679 --> 0:13:02.360 know have any way of guessing what it is. But 0:13:02.520 --> 0:13:07.320 because it's an inherent property of this particular material and 0:13:07.360 --> 0:13:10.440 it's really dependent upon the molecular composition of whatever that 0:13:10.520 --> 0:13:14.480 material is, UM, then we can make start making guesses 0:13:14.480 --> 0:13:17.760 based on that phase shift. UM. And it's yeah, the 0:13:17.760 --> 0:13:19.760 face shift, you know, with it being that difference in 0:13:19.800 --> 0:13:24.520 timing between the transmitters frequency UH and the frequency of 0:13:24.559 --> 0:13:29.080 the magnetic wave that's generated by the object. UM. You 0:13:29.120 --> 0:13:33.679 know it's these are sort of ranges, right like if 0:13:33.720 --> 0:13:36.320 it if it's a certain range there, then the male 0:13:36.400 --> 0:13:39.520 detector can give a best guess as to what that 0:13:39.600 --> 0:13:45.240 material maybe. So there's never necessarily a guarantee that whatever 0:13:45.280 --> 0:13:48.920 it is you've detected is specifically going to be you know, 0:13:49.000 --> 0:13:52.560 aluminum versus goal or whatever. But it's a it's an indicator, 0:13:52.600 --> 0:13:56.040 so that, uh, it gives you at least the idea 0:13:56.040 --> 0:13:59.000 of you know, is that you measure risk versus reward, right, 0:13:59.760 --> 0:14:04.040 the risk of exhausting yourself digging up useless junk versus 0:14:04.080 --> 0:14:08.520 the reward of possibly finding something that is of true value. Yes, 0:14:08.760 --> 0:14:11.800 so that's really the whole purpose of this anyways, just 0:14:11.880 --> 0:14:14.480 you know, to kind of tune in on that beep 0:14:14.640 --> 0:14:17.000 and make it more meaningful so that you know, you 0:14:17.040 --> 0:14:21.640 don't waste your time digging up little poll tabs from 0:14:21.720 --> 0:14:27.360 soda cans. Yeah. Now, yeah, if you have a higher inductance, 0:14:27.640 --> 0:14:30.440 it's going to create a larger phase shift, and lower 0:14:30.440 --> 0:14:34.960 inductance has a smaller phase shift. Now, metal detectors use 0:14:35.080 --> 0:14:40.680 a phase demodulator to read this, and uh, what that 0:14:41.160 --> 0:14:45.720 creates is discrimination. Yeah, yeah, I know it's terrible, but 0:14:46.280 --> 0:14:49.560 oh no, not within metal detectors. It's okay, yeah, because 0:14:49.560 --> 0:14:52.800 the thing is, a good metal detector will allow you 0:14:52.880 --> 0:14:57.520 to filter out stuff that you don't want because the 0:14:57.560 --> 0:14:59.920 metal detector, if you said it at a certain setting 0:15:00.080 --> 0:15:02.920 and say, you know, I'm really looking for metals that 0:15:02.960 --> 0:15:06.600 fall within this range, yeah, perhaps gold. I've actually seen 0:15:07.280 --> 0:15:10.920 uh metal detector booths and they'll have like this giant 0:15:11.000 --> 0:15:14.920 jar of class rings that people have lost, which is 0:15:14.920 --> 0:15:17.240 sort of a you know, reminder that you know, hey, 0:15:17.280 --> 0:15:19.360 you you can find stuff if you just take your 0:15:19.360 --> 0:15:22.840 mel to Of course people look at you funny, but yeah, 0:15:23.040 --> 0:15:24.960 that way. That way. Let's say that you're out there 0:15:25.000 --> 0:15:27.840 looking for something specific, you can you know, some meld 0:15:27.880 --> 0:15:30.960 detectors have settings where you can you can tell the 0:15:31.000 --> 0:15:34.760 meld detector to ignore anything outside of a particular range 0:15:34.800 --> 0:15:37.200 of frequencies. So, in other words, you're saying, you might 0:15:37.240 --> 0:15:41.560 say I'm only interested in finding silver. Let's say, So 0:15:41.680 --> 0:15:43.560 what I'll do is I'll set my meld detector so 0:15:43.640 --> 0:15:47.640 that it'll it'll only uh activate, it will only alert 0:15:47.760 --> 0:15:53.640 me if something that generates a magnetic frequency similar to 0:15:53.720 --> 0:15:57.120 that of silver is encountered by the metal detector. So, 0:15:57.120 --> 0:15:59.000 in other words, but you might you might pass over 0:15:59.040 --> 0:16:02.480 a gold deposit and nothing happens. But as soon as 0:16:02.520 --> 0:16:05.640 you go over that that silver half dollar. But and 0:16:05.680 --> 0:16:07.600 then you dig it up and you're like, hey, look 0:16:07.600 --> 0:16:11.120 I'm rich. I Meanwhile, the gold guy behind you was like, sucker. 0:16:12.520 --> 0:16:15.160 Well that's that. That can be called notching. Basically, you 0:16:15.200 --> 0:16:18.480 set it for a if you imagine a scale, uh 0:16:18.520 --> 0:16:21.320 you know, one notch on that scale, or some of 0:16:21.320 --> 0:16:23.920 the more sophisticated metal detectors will allow you to set 0:16:24.640 --> 0:16:26.560 more than one notch, right, So that way you could 0:16:26.560 --> 0:16:29.240 look for both silver and gold and you'd say, ha ha, 0:16:29.720 --> 0:16:34.480 Mr smarty gold pants. Um. Now that's that's the VLF. 0:16:35.840 --> 0:16:39.240 The post induction metal detectors a little bit different. Yeah, 0:16:39.240 --> 0:16:42.200 it uses only a single coil, or it can use 0:16:42.240 --> 0:16:45.280 multiple coils working at the same time. Yeah, but there 0:16:45.280 --> 0:16:47.880 these are these are coils that haven't that don't have 0:16:47.920 --> 0:16:50.920 that shielding. It's not like you have a transmitter coil 0:16:51.000 --> 0:16:54.600 and then a receiver coil, and all of these coils 0:16:54.600 --> 0:17:00.640 are generating very quick bursts of electric city, which of 0:17:00.680 --> 0:17:05.439 course creates a very sharp magnetic wave. And uh so 0:17:05.480 --> 0:17:07.760 it's just a really quick spike and then what will 0:17:07.800 --> 0:17:10.920 happen is that magnetic wave if it encounters a metal object. Again, 0:17:11.160 --> 0:17:13.200 that metal object will have to will generate its own 0:17:13.240 --> 0:17:17.960 magnetic wave and the metal detector will pick up on that, 0:17:18.040 --> 0:17:20.320 and it's all it's kind of like an echo. Right, 0:17:20.880 --> 0:17:23.520 It's kind of like an echo, right, thank you. So 0:17:24.680 --> 0:17:27.240 if you think about it that way, it's it's like 0:17:27.840 --> 0:17:30.960 sending out a signal and waiting for something to bounce back. Yeah, 0:17:30.960 --> 0:17:33.240 but it's very fast. I mean the average is about 0:17:33.280 --> 0:17:37.520 a hundred pulses per second, which is yeah, fairly rapid, 0:17:37.560 --> 0:17:41.360 pretty quick. And then you're looking for the reflected pulse, yes, 0:17:41.640 --> 0:17:44.960 which is what the the object that is under the 0:17:45.000 --> 0:17:50.159 ground or wherever. Uh, that's the the the pulse that 0:17:50.240 --> 0:17:53.040 it generates in response to the one that came from 0:17:53.080 --> 0:17:56.440 the metal detector. Yeah. Now it uses a these these 0:17:56.480 --> 0:17:59.280 types of metal detectors use a sampling circuit basically trying 0:17:59.280 --> 0:18:03.120 to deter whether it's actually metal that you're finding or 0:18:03.200 --> 0:18:05.840 something else, some other type of magnetic field that is 0:18:05.880 --> 0:18:09.080 interfering with this signal. And it's basically judging that based 0:18:09.119 --> 0:18:15.640 on the amount of time it takes U two to reflect. Um. Yeah, 0:18:15.640 --> 0:18:17.480 that's another thing that we should point out is that 0:18:17.520 --> 0:18:21.199 metal detectors can encounter lots of different kinds of interference, 0:18:22.000 --> 0:18:24.400 not just the composition of the soil. But let's say 0:18:24.400 --> 0:18:28.119 that you happen to cross over where an electrical cable 0:18:28.160 --> 0:18:32.120 has been buried. That could cause a problem. Your male 0:18:32.200 --> 0:18:34.920 detector might think that, hey, look there's gold in them 0:18:34.920 --> 0:18:38.600 the our hills, and truth, what you've hit is the 0:18:38.680 --> 0:18:41.240 power line, which you don't want to dig that up. No, 0:18:41.600 --> 0:18:46.240 it could result in everything from death, which is in 0:18:46.320 --> 0:18:50.479 the metal detection BIS we call a bad thing, or 0:18:50.480 --> 0:18:54.600 it could result in or and or it could result 0:18:55.080 --> 0:19:00.520 in an entire region losing electricity. That's also a bad thing. 0:19:01.320 --> 0:19:03.600 That's that's a very good point. I mean, these these 0:19:03.600 --> 0:19:06.159 metal detectures are not only incredibly useful, they can be 0:19:06.160 --> 0:19:08.200 a lot of fun. A lot of hobbyists love them. 0:19:09.280 --> 0:19:12.040 But you do have to be very very careful. Um 0:19:12.160 --> 0:19:15.040 and it's good to know your the territory to quote 0:19:15.040 --> 0:19:17.919 a certain musical, but yeah, I mean you need to 0:19:17.920 --> 0:19:21.159 know the territory. You gotta know where you're you're digging 0:19:21.640 --> 0:19:24.880 because you you really could get hurt. Honestly, I got 0:19:24.960 --> 0:19:28.440 Rock Island going through my head. Cash for the merchant 0:19:28.560 --> 0:19:33.920 dies a. Sorry, all right. So we have an integrator 0:19:34.680 --> 0:19:39.040 on these, on these pulse induction metal detectives, and that's 0:19:39.119 --> 0:19:42.159 reading the signals from the sampling circuit and converting them 0:19:42.240 --> 0:19:45.320 to d C. That's not current, yeah, not the district 0:19:45.359 --> 0:19:48.560 of Columbia. Yeah, not not a comic book publisher either. 0:19:48.840 --> 0:19:51.359 And that's feeding into it the audio circuit, and that 0:19:51.560 --> 0:19:55.520 is what beats. Yeah, that's the stuff what beats. The 0:19:55.880 --> 0:19:59.119 thing is, uh, these are very good at detecting metal, 0:19:59.200 --> 0:20:01.919 but they're not very good at discriminating between different types 0:20:01.920 --> 0:20:05.639 of metal. UM, So you're not going to get the 0:20:06.240 --> 0:20:09.040 level of precision that you would get with the VLF 0:20:09.800 --> 0:20:13.320 metal detector. But you know, they also you've got to 0:20:13.359 --> 0:20:16.000 remember that these different types of detectors, while some of 0:20:16.040 --> 0:20:18.800 them may work in conditions that others do not, there's 0:20:18.880 --> 0:20:23.520 there's also a price range here as well. Oh yes, yes, now, yeah, 0:20:23.520 --> 0:20:29.040 the beat frequency oscillator metal detectors can be uh fairly affordable. Um. 0:20:29.080 --> 0:20:31.679 They also used two coils, but one is in the 0:20:31.720 --> 0:20:33.720 search head and the other one is actually in the 0:20:33.760 --> 0:20:37.480 control box. Um. They're connected to an oscillator that as 0:20:38.440 --> 0:20:43.080 pulsing UM many many times per second, thousands of times 0:20:43.080 --> 0:20:46.800 per second um. And and the and the frequency of 0:20:46.880 --> 0:20:49.200 the one that's inside the control box and the one 0:20:49.240 --> 0:20:53.600 that's inside the actual detector are slightly offset. They're not 0:20:53.800 --> 0:20:58.919 in sync or Backstreet boys or oh you got the 0:20:58.920 --> 0:21:05.359 other one I was gonna do so yeah, well, ironically 0:21:05.480 --> 0:21:09.000 enough to our our current part of the conversation, they 0:21:09.240 --> 0:21:12.000 create radio waves, um, and then the receiver in the 0:21:12.040 --> 0:21:16.439 control box uh picks that up and plays tones to 0:21:16.600 --> 0:21:20.479 let you know when you're you're coming into range of metal, right, 0:21:20.520 --> 0:21:25.639 Because what's happening is that when the metal encounters this uh, 0:21:25.720 --> 0:21:30.080 this this this electromagnetic field that is going to alter 0:21:30.640 --> 0:21:34.080 that radio wave. And so what's really listening for our 0:21:34.160 --> 0:21:37.359 changes in the sound that you're hearing. The change in 0:21:37.400 --> 0:21:41.280 the sound indicates that you have encountered something that is 0:21:41.400 --> 0:21:44.560 generating this magnetic field. Because of the one year generating, 0:21:44.840 --> 0:21:48.960 they know what they're going through. UM. So yeah, I 0:21:48.960 --> 0:21:53.280 mean detectors killed the radio star. But these these uh, 0:21:53.480 --> 0:21:56.880 like I said, these are a lot cheaper to manufacture. 0:21:56.960 --> 0:22:00.439 And therefore, if you are uh interested in getting your 0:22:00.440 --> 0:22:04.280 feet wet uh and the metal detector the thing is 0:22:04.320 --> 0:22:06.600 a hobby, you might consider this, but they're they're far 0:22:06.720 --> 0:22:09.919 less accurate in terms of being able to give you 0:22:09.920 --> 0:22:14.119 any kind of discrimination or any really any real control. 0:22:14.800 --> 0:22:17.880 UM they actually use. These are the types of metal 0:22:17.880 --> 0:22:21.160 detectors that you the handheld detectors that they use the airport. 0:22:22.040 --> 0:22:24.880 Um you know, if you walk through the scanner and 0:22:24.880 --> 0:22:26.320 and then yeah, that's the type they use in the 0:22:26.400 --> 0:22:29.680 one because they don't really need to know whether it's 0:22:29.720 --> 0:22:32.320 gold or iron. They just want to know what it 0:22:32.400 --> 0:22:35.080 is that you've got now once once, once something beeps, 0:22:35.080 --> 0:22:37.000 then they can say, all right, well let's see what 0:22:37.080 --> 0:22:41.120 that is. They don't, you know, necessarily need to know immediately. Yeah, 0:22:41.160 --> 0:22:44.680 And the metal detectors the frames at the airport, they 0:22:44.840 --> 0:22:47.680 work on essentially the same principles we've talked about here. 0:22:48.119 --> 0:22:51.080 They're generating electromagnetic fields, which of course has brought up 0:22:51.119 --> 0:22:56.080 some concerns with people who may have UH devices like 0:22:56.160 --> 0:22:59.400 medical devices that could react to electromagnetic fields. That's why 0:22:59.440 --> 0:23:02.920 you occasion we hear about UH folks like that having 0:23:02.960 --> 0:23:06.560 to go through like a pat down security as opposed 0:23:06.560 --> 0:23:09.200 to a metal detector, just because of the concern that 0:23:09.280 --> 0:23:13.040 it could interfere with a medical device. Right right now, 0:23:13.400 --> 0:23:16.359 with with all of these UM, what you're gonna find 0:23:16.400 --> 0:23:19.440 depends on the type of metal detector, the type of 0:23:19.760 --> 0:23:23.080 metal that you're looking for, about how big it is, 0:23:23.119 --> 0:23:25.959 the kind of makeup of the soil, um any kind 0:23:25.960 --> 0:23:30.240 of interference from other objects, and the halo, which is basically, 0:23:30.760 --> 0:23:33.159 you know, if you have a piece of metal in 0:23:33.200 --> 0:23:36.520 the soil, it's going to read a little bit differently, 0:23:36.520 --> 0:23:38.919 it's going to it's going to register is larger than 0:23:38.960 --> 0:23:42.320 it actually is. Yeah, it's because those interesting things. Yeah, 0:23:42.400 --> 0:23:45.240 they I could see your halo. I was I was waiting. 0:23:45.560 --> 0:23:48.560 I was trying so hard not to go into that. 0:23:48.920 --> 0:23:52.920 We've done so many songs references in this podcast, it's crazy, 0:23:53.040 --> 0:23:56.199 and this might be our like our most intense that 0:23:56.440 --> 0:23:59.520 the funny thing reference per minute other than the first one. 0:23:59.560 --> 0:24:03.920 None of them have been metal. That's true, that's so. 0:24:04.200 --> 0:24:06.439 But yeah, now that it is, really the halo effect 0:24:06.480 --> 0:24:08.800