This video has been discussed on hackaday. See hackaday.com/2019/11/26/progressive-or-thrash-how-metal-detectors-discriminate/#comments for more discussion on the subject.
People who want to make their own detectors sometimes ask us for the explanation of how it works. Now I know where to point them. Very good explanation, thanks a lot!
I've done some light research on this subject before and mostly came up with old schematics that I kinda gleaned were doing some kind of phase detection but with no explanation of the working principle of anything or how the coils interact. Great explanation and nothing beats a live demo with a scope to get some intuition of how the process works when it comes to these kind of things.
Ive been using detectors since the early 70s. With the early detecors you used a constant threshold and listening closely for the Phase Shift. The term we used was "Getting your ears right". After awhile you can mentally picture the graph and negative positive response curves in your head. Its was self inflicted Pavlonian Training.😂 THIS IS the BEST 🎉🎉🎉 description of coil operation on RUclips. Certain old Whites Detectors could be precisely "dialed in" to do just that, but do it extremely well.
I realize this is 4 years old but wanted to comment anyway. WOW, just WOW. Thank you. As a new hobbyist this is great information and allows my mind to understand how my detector works. Truly appreciate the time and attention you took to make this amazing learning experience.
@@ThePOSMwhat's the age of the video got to do with it? A lot of people don't respond back to old videos and some people don't even make them after years and move on from RUclips. I seldom get an answer back from the content creator on videos that are many years old
my day job is building coils for MRI but I got interested in metal detectors after losing my phone in a lake and seeking to build one for the retrieval. In MRI, we overlap coils to cancel inductive coupling all the time. It's wonderful to see how this is applied to detecting metals, and knowledge of how different metals behave in a magnetic field made understanding the phase shift intuitive. Thanks for the great explanation!
Congratulations for this complete analysys of working of detectors . Very in deep and very good to understand , we appreciate your time and effort for this video . Thank you again
To better discriminate the Foucault currents (you call them eddy currents) you must use a third coil driven with 1 - 2 Hz signal, at pretty high intensity, 10 - 20 Ampere. This eliminates the need to move the coil assembly over the soil. Some used a neodimium magnet driven by a motor, but this produces a lot of interferences and the 2 Hz signal is hard to subtract in the signal processor. A better way is to use two independent 19 KHz oscillators, and drive them so there is one 360 degree phase rotation per second of one oscillator with respect to the other. This make possible to measure the AL (permittivity / reluctance) and hysteresis separately. A modern 50 pence Cortex processor can do some stupendous tricks with the use of a FFT algorithm. I'm an analogue die-hard designer but I must admit that a good written code on a microprocessor seems to do miracles sometime. Enjoy the fun...
I just recently ran across and subbed your channel being an electronics guy interested in telescope optics. I use the sister machine with the AT Gold in California and Arizona. I call the detector an exercise machine getting me off into the wilds cleaning up bird shot and bullet fragments ;) It does indeed give fair indication of what denomination coin or pull tab will emerge. The ring find is a good lesson to dig each target and in time the aural attack will provide a sense that this pull tab is different. Wonderful channel!!!
This video is exactly what i was looking for. Ive studied electromagnetism in uni and highschool so i managed to grasp most of the science behind it. Thanks
I've been wanting to, and delaying, build a metal detector for years. The biggest obstacle, not having an oscilloscope, was resolved a few years back, now I just need to start experimenting, and when I do decide to move my lazy ass and start working, I believe this video will be of great help.
Very interesting video! I believe this is the same effect used in shaded pole induction machines, which never made intuitive sense to me until now. They use a copper ring in the flux path of a single phase induction motor to create a weak additional phase to get the motor spinning (otherwise the magnetic field just alternates without spinning the motor).
I was always curious how these things could differentiate materials and your explanation satisfied my curiosity. I'm tempted to borrow a detector from a friend and give it a try sometime!
Well explained. Thank you for sharing. This is the first time seeing Hilversum written. I heard the name first in a Van Morrison song "In the days before rock 'n' roll".
I just recently started this hobby. This info helps a lot. My most exciting hunt starts today. My father just bought a new house just outside of historical Sackets Harbor. Metal detecting in the village is not aloud, but being his property is just outside the village, im good to go. Fingers crossed i find some really good finds.
Good luck, gernerally there is a reason why metal detecting is not allowed in certain places. There might be a lot to find, but it can also be because you are likely to dig up dead peope or dangerous stuff.
@@HuygensOptics ill be very careful in this endeavor. The historical significance is due to the war of 1812. The property is actually 2 miles north of the "battlefield". Im not an expert by any means, but after speaking to a few people that are, ive been told that the chances of finding any type of live ordinance will be pretty slim. I found out this morning that the original owners great grandfather was a blacksmith. Hes on his way over now to show me where they believe his shop was. The property is pretty big (in my opinion) at 12 acres and the original farmstead/house/shop is not where the current house sits. Ill let you know if anything exciting is found.
Goedemiddag. Thank you for this video its very informative. Have to admit i dont understand everything though. Bit frustrating because i realy badly want to understand it. I recently built a PI metal detector using 3d printed parts , it works ok using a colpitts ocilator and arduino. It works well enough to find the pipes in my house walls, but the metal has to be about the same length as the coil before it will detect it about 20cm , smaller objects has to litrally enter the center of the coil. The theory and methods behind metal detection has become an obsession 😀. Groete from a fellow afrikaner dutch descendant. Goeie werk en hou so aan! Lekker!
Hello Martin, So the video is about VLF-technology (Very Low Frequency), PI detectors work on a different principle as you likely know. I also build a PI detection setup and, like you, found that it is actually not that easy to achieve a high sensitivity. Also, evaluation of the rise and decay in the magnetic induction caused by the pulse was not as easy as just examining the phase shift observed with VLF, so discrimination is hard. If you are digging for gold in an iron-rich ground, PI is the technology to use, but even then you need all kinds of tricks to filter out the signal from the noise if you want to go deep. Here in the Netherlands most PI detectors are not very usefull, because of the generally limited dicrimination between treasure and trash. So that is why I don't own one. Good luck detecting! Cheers, Jeroen
Someone needs to make a open-source high end metal detector, some amazing stuff could be done, I'm imagining a system with GPS and accelerometers that could produce "maps" of underground responses, and with fpga signal processing I'm sure that it would be possible to do some incredible discrimination.
Being a retired pipeline excavator, I can only imagine how valuable a map of underground fixtures, utilities, etc., is going to be to future generations of hoehand s...
Nice video, curious as to why gold was left out. Would be interested in the science behind why gold and aluminum ring up similarly, and if there is a way to potentially distinguish between the two with a detector.
In principle it is possible to distinguish between the two, gold is diamagnetic whereas aluminium is paramagnetic. They have approx. the same conductivity, and this will be the mayor contribution to the phase shift in VLF detection. An advanced PI (pulse induction) detector should be able to detect the difference between the two materials.
I recently purchased a late model surplus military detector that will pick up the very small particulate metal that is found in plastic explosives. It will detect metal that is literally as small as a single grain of sand, and it will do this at considerable distances away from the search coil. Presumably it does this based on the same principle of physics that is described in this well made video. However, i'm curious to know if the coil on this machine is considerably different on this detector or if the electronics in the control head account for this extreme sensitivity to a nearly invisible amount of metal. It doesn't seem possible that a detector could pick up the extremely tiny amounts of metal that this thing will, yet somehow it does this very easily. Great video!
Excellent video and very nice experiments. Please allow me however to express some doubts about the interpretation: I don't think that diamagnetism or paramagnetism play any role at all: they are both extremely weak effects with susceptibilities in the 10^-4 range. Moreover, many non-metals are diamagnetic and/or paramagnetic and do not give any response to a metal detector. My understanding is that the phase shift is mostly determined by the decay time of the eddy currents in the object, which is given by L/R, the ratio of the inductance to the resistance of the object. Thick silver/copper/aluminium objects have an L/R of order 100 microseconds, while iron or aluminum foil have L/R of less than 10microseconds. Compare these to the period of the 15kHz emission, and you get the high L/R giving a lagging disturbance with a big phase shift and the low L/R an immediate disturbance with little phase shift.
I agree that the main detection mechanism for most metal detectors is based on conduction and eddy currents. However, conductivity alone cannot explain the differences in phase shift between metals. I'm not sure to which non-metals you refer, but conductivity is not always required for detection with a metal detector. Take ferrite: non conductive, paramagnetic and it gives a huge signal. Not all metal detectors will see it though, due to discrimination settings.
@@HuygensOptics I was thinking of liquid oxygen, but actually that's an exceptional case, there are indeed very few non-metallic paramagnetic materials. On the other hand, every material is diamagnetic. Ferrite is ferromagnetic and ferromagnetism completely overwhelms paramagnetism if present. My understanding is that only conduction and ferromagnetism give a response in metal detectors, with conduction giving a phase shift between 0 and 180 degrees (twice the phase shift of the equivalent LR circuit) and ferromagnetism contributes with 0 phase shift (if it is instantaneous compared to the timescale of the oscillating field - but I'm not sure about the latter..)
@@rgco2266 that is correct, ferrite shows 0 phase shift (or very close to that value), as is also shown in the video. In the standard detection modes of the Garrett it is not always detected due to this exceptional behaviour. However, in the "pinpoint mode", it is always detected very strongly because only signal is considered and phase is ignored. Thanks for the additional information you supplied.
TOP Video eindelijk een goede en duidelijke uitleg. En een helehoop bij geleerd ik moet het dus sneller bewegen. Als je films ziet waar sommige met dat ding als een malle tekeer gaan denk je uitslovers maar het blijkt dat het zo moet.. lol.. Met die spoelen was het gene ik beter wilde begrijpen en dat hebt u super duidelijk uitgelegt. Ik heb net een week een detector een MD-3010ii uit china dacht eenk kijken of ik dit leuk vindt. Maar hij werkt niet naar behoren en wat blijkt er is iets met een spoel die niet werkt. Er zit een stekker met 5 pins in 2x2 voor spoelen en een vrij. Alleen hebben ze een kabel verkeerd geslodeerd en een zou dan niet moeten werken. Hoewel hij wel iets doet als ik over metaal ga en ook de PP (pinpoint) werkt ook fijtloos dus ben ik op zoek naar het antwoord hoe zit het nu. Op de printplaat komen 4 kabels aan dus ik dacht 2 voor elke spoel en met die gedachten zou hij dan niet kunnen werken of zit ik helemaal fout?? Groeten, Andre
Great presentation. Interesting point for what ever reason gold was omitted from your list of metals. Being that gold is one of the most desired treasure metals we detect for. Would have been nice to compare the conductivity of silver verses gold on your list. Cheers, #SeattleRingHunter
This is my kinda cake.... LOVE IT!! Well done *SIR* Learned alot and amazed in how much i had wrong on the principle. Especialy that there s one recepteror coil and one transmitting . i was under the impression that the two coils alternate between beying a receptor and emmitor coil . thanks for clearing that one out . I had a garret detector , nowerday i hunt inland with XP DEUS and on salty beaches with an Minelab equinox 800 . Would love to see you analyze the FBS method they use , sending 5 different frequencys at once and eliminating all interferrence with the metalions present in salt. would love to loan my minelab detector , so you zouldn't have to buy one ;) these are topics i litrteraly lay awake of at night , as i dream of making my own metaldetector ..one day greetings from Zeeuws Vlaanderen hihi Johny Geerts
You explained well, but I was surprised that gold was not among the metals that were tested. Please explain how much gold is known according to your experience.
Indication: probably in older models changing emitter and phased indication to square wave and operation amplifier substraction stage followed by accumulator operation amplifier stage which output is between 0 V to DC positive and 0 V = 180° shift indication would be scored as indicative ID 100.
New comments on an old post are unlikely to be detected, but I wonder if a double-D detector could be used to find sunken submarines or crashed airplanes. The search coils could be huge, perhaps 10 meters, and the frequency could be very low, perhaps 100 Hz in order to penetrate seawater. Several issues would be if the detector sensitivity could match a SQUID or MAD magnetometer, and how big the search cone would be.
Have you thought about studying the shape and style of coil on the performance of detection, by making micro coils for the detector? Say ,50-75mm coils? I had the idea of using two pancake serpentine coils have one zig while the other zags! Alternating the coil around ,8 x 20 mm dowels, bone coul is on the outside of the dowel with the other on the inside! So each dowel is like a small DD coil, this could boost performance especially with a large 1000mm boil with the use of 100mm dowels! So there is basically 8 x100 mm coils. Could this be effective??
Part of the power of the DD coil is that it allows you to better locate an object during scanning it over the ground sideways. You would miss that feature if you were to create multiple small coils and add them together in a single coil.
Is there some kind of accelerometer to detect whether you are sweeping L-->R or R -->L ? I can imagine that with a single Tx and single Rx coil, for the same sweep-direction, you would get an opposite polarity for (say) aluminium vs. steel. Am I missing sth here?
I did not measure it, however it's quite high. Where the transmission coil only has 10-20 windings, the reception coil can have many hundreds of windings. If I think of it in the coming days, I will try to measure the actual value.
@@Ktulu789 hola buen dia amigo quisiera saber si tene el lista de los componentes electrónicos del detector de metales terminator 3 el que tiene 7 imtegrados de catorce pata y un integrado de 8 pata
Anyone knows what's the name of the particular coil at 5:35 ? This is a really heplful and well made video about the working principle of a metal detecting device. Thank you very much.
Thank you, hard to understand for me but interesting. Do you know what happens when you adjust the disc higher on the machine? Because it influences the detection depth if you ad more discrimination to the machine.
I'm not sure, I think increasing the discrimination will generally lead to lower detection sensitivity. But with the detector I own I can only set rejection of specific target ID-ranges, not a general discrimination level.
Great video and thanks for taking the time and effort to set it all up. The results really correlate with my metal detecting IDs (Minelab Equinox) but I wish you'd included copper as that's such a commonly found metal. I suppose being a good conductor and diamagnetic it'll be similar to silver?
Your equinox runs using 2 separate frequencies simultaneously. The lower frequency is more sensitive to copper and silver it targets higher up the VDI scale where as the higher frequency is more sensitive to the lower frequency. The two frequencies have a huge difference in the shift of the targets phase. When it detects a target it reads the low frequencies shift and strength of the signal. Then it does the same with the high frequency. There is a processor that calculates the difference between the two and assigns it a VDI (visual target identification) and generally it is pretty accurate but it doesn't "suggest" one type of a target over the other. The Whites DFX operates sort of the same BUT it has a feature which allows you to read the shift in the phase which damn near tells you exactly what it is which a much higher degree of accuracy. I'll give you an example. If the VDI reads 20 - 22 it is could be a nickel or a pulltab. When the DC Phase shift is turned on you squeeze a trigger and pinpoint it. If its a nickel the DC Phase will read 39 -42 +/- depending on ground minerals. If the DC Phase reads in the mid 60's to low 70's its a piece of modern aluminum. If its really low like in the teens its old aluminum. Its amazingly accurate once you remember what the targets phase read. But before that I would already know its a nickel because there is a bar graft from 1 to 4 bars. Aluminum will give 1 bar maybe 2 if its a bigger piece. The nickel will run to the top and stack all 4 bars or maybe 3 if its deep. Now if it stacks 4 bars but the DC Phase hits the 50's to 60's you may want to call it a pull tab with the high DC Phase but being it stacked 4 bars and not 1 it is a nickel between 1942-1945 because its a war nickel that have a percentage of silver in it so between the VDI, the DC Phase and the bar graph that Whites calls it the signagraph those 3 points of ID can tell you everything about the coin but the date. And still in the case of war nickels it zero's that down to a few years. VDI of high 60's with DC Phase of 67 to 72 is a penny from 1982 until present. If the VDI hit the upper 70's and the DC Phase is in the high 70's its a copper penny from 1982 and earlier. In '82 both designs were made half way through the season to save copper and instead made it from zinc then cladded it with copper. If the copper plate is intact those numbers above are correct. If it starts to bubble or corrode then the numbers drop very fast on the DC Phase reading. My friends refused to bet me even 1 dime anymore on calling the targets before I dig. The very last time I bet with 2 of my buddies who swept their detectors over it, one calling it a screw cap and the other called it piece of aluminum or a foil ball its a non dig but I called it a penny and to dig it they jumped on that bet in a second Then showing off a little I said its going to be a penny from 1982 or newer it's a "zincoln" the nickname for the zinc pennys and a penny with bubbles popping off the surface dated 1995 came out they were stunned on how I called it right on a clear non penny signal. It was the detector and the 3 points of ID that made that one of the best detectors ever for its time. It had so many settings that new hunters didn't understand and they could adjust it and cause it to lose depth until you learned it and since people had hard enough time coughing up $1,200 for a detector they wanted to be able to turn it on and go. And though it had factory presets for learners the power level was set in the high 60's so people naturally cranked it up higher without changing other setting and all it did was chatter. Whites omitted some features, made it more learner friendly and it became the V3i. That machine runs 3 frequencies and even shows you which frequency is dominate which gives you a hint right their if its a coin or not. But they have come a long way. They also use concentric coils not DD's which can detect deeper but they also see more trash and minerals around the target. The Equinox 800 is a pretty good detector to so you'll do well with it. One tip for all its worth in heavy iron or black sand power down just a bit. It barely loses sensitivity or depth but it greatly cuts down on the noisy chatter. Detectors rarely can handle cranking it to the max without falsing. Good Luck hunting
Also if you want to learn a trick. Sweep over a pulltab and read the ID. Then cut that same pull tab and straighten it out. Now its the same piece, same metal content, same mass (volume of metal) but what is it reading now? And why???
@@stevenallen9592 Thanks for the very detailed and in-depth replies! I'm guessing with all your talk of nickel you're on the wrong side of the Atlantic to be digging up Medieval or Roman coins. That's interesting about the White's detector - but in practice although it's fun to predict what you're about to dig, how often do you (unless it's iron) actuually say nope, not digging that. With the Nox 800 if I dug only 4-7 (cut hammered quarters), 8-10 (cut halves), 12 (hammered pennies) and 21-22 (milled coins) I'd probably recover over 95% of what I keep without digging up all the other crap. Below 4, 11 and 13-17 are nearly always rubbish (I include buttons and musket balls as rubbbish). Over 21 is usually large copper or aluminium. But a large hammered coin such as a shilling will ring at around 18 or higher, Roman coind perhaps 14-18, artefacts such as Roman brooches could be anything, gold can be low ID, so I dig a lot of crap despite those items being very uncommon. So I dig a lot of crap knowing I'm about to dig crap just in case it isn''t crap! I started detecting in the 1970s with C-Scope VLF machines. They had no ID, just an analogue meter at best. There were two knobs - volume and discrimination and there was a reset button for ground balance. I remember though I could discriminate quite accurately by the consonants of the tones. Coins tended to have a softer edge whereas iron or lead had hard edges. It's similar with the Nox but not as obvious or intuitive. But watching Holzhammer Sagas RUclips channel I think the Deus in Lite mode has similar qualities. I wonder if there's still a place for those old analogue detectors but with better deeper coils. My 22 year old BMW car runs just fine without reverse camera, lane tracking, telling me when to change gear etc. Similarly I wonder if all the software embedded in these detectors i really necessary
@@stefkuna I re read what I posted to remember what the topic was and I caught a bad typo where I wrote the higher frequency is more sensitive to the lower frequencies lol. I probably wrote that apply late at night half a sleep. It wouldn't the my first time. I meant th3 higher frequencies like the lower VDI targets. I'm familiar with the "NOX" in the sense of its dual frequencies and iron cancellation and other features but I haven't used one so I don't know where what targets ID at. I was trying to make a point how those targets that have the same VDI or ID number range like American Nickels reading the same as some gold rings or even aluminum. When using a multi frequency detector the computer tries to determine which frequency is responding better and leans towards the ID of that frequency scale. Air testing doesn't take in account the fact there's no minerals or trash involved with the signal or its ID. I'm a little familiar with the difference in the soil in England as opposed to North America especially in the original colonial states. There's actually been a few hammered silvers pop up but its thought that someone had them collecting and it got lost centuries later as opposed to their when its lost not long after being struck. Being as old as you area is you've built up centuries of metal and of coarse the worst being iron. You also have that hit ground they call coke, right? We have spots of it but its not plowed everywhere its from native American fire pits because much of it is actually organic material mostly charred wood from fire pits. Then over the years this "coke" is plowed all over, rain spreader some and some areas of older pits that were deep is really bad. The lower frequency which is more sensitive on thicker silver or copper coins don't hit those very deep because of that hot soil and can miss those little hammered silver or small gold. Then the higher frequency with chatters a little more is better on seeing those tiny silvers that the lower frequency struggles with because of the tough ground but it loses depth on coppers. The detector also gets thrown off by the ground reading. You might balance it and track on it but the value of the ground changes a little more erratically because its not a metal that creates a magnetic response more as it silences it like a ferrite rod. Nothing here even the few hot spot burn pits are enough to deal with like you deal with. But another point that I really wanted to bring up was the shift in the phase. The microprocessor can figure out which frequency is responding better and do its calculations but having that control of knowing the difference between the phase on two targets with the same VDI make for an extremely accurate ID. I used to talk to a guy named Jimmy "Sierra" Normandy. He worked with Whites and helped the development of several detectors starti,g with gold. He told the nickname Jimmy Sierra because he was/is a gold prospector in the Sierra mountains in California. I picked his brain apart to learn these settings on the DFX. He used to field test for Whites in England and he started these paid detecting hunts where about 10 or 12 guys paid at that time (2006+/-) around $2,000 US dollars and the money went to a farmer over there to hunt fields that have produced hoards in the past. On 2008 I almost went if it weren't for the conditions. The farmer got paid to rent the land AND a cut of the value of the find. That I was OK with. Then everything found had to stay for months for the government to go through it, decide if they want it, take a cut if the laws there required it. Then either bought them and paid what they call fair value or set the value and took their cut. Then if they didn't keep the common stuff the contact there mailed the finds minus what the government took and what deal you make with the owner paying him the money or a share of the coins at his call. Ugh and even that I said well that's how it goes. What I didn't like was that a person who spent years to get pretty good could hit some valuable finds and a guy who goes just to see the country side and maybe not hunt much gets to get an equal share of what's found even if they found nothing. That didn't sit well when I heard from people who attended these hunts before that some guys who are wealthy would go and good around in hopes one of the hunters hit something valuable and he gets as much as the guy who dug it? The DFX didn't go over well there because it takes time to really know what its doing when you adjust the sweep speed, or the track speed, inhibit it from tracking and manually track etc etc etc. It was not a new owner friendly unless you spent a long time and had a lot of patience. I think Minelabs popular there. The Deus even some Makro's are preferred detectors there. You know what's more popular there then I would. Jimmy told me a tip about hunting with fresh plowed ground after its rolled and it rained. After the rain the coke leaves s film on the top of the ground. He said to walk through it dragging your foot and break up that film because it acts like shielding does in a coil and the detector was more stable by breaking that later if coke. It makes sense to me being it allows the magnetic field to go down with less interference. One day I'm going to go on a hunt there. I have a half sister that lives there. My dad met an English woman during the war and her mother didn't come to the states when my father was withdrawn after the war. I've met her being she would come to the states on and off but she's kept the land her families owned for a long time. I specifically asked her, (it was more like I begged her lol) not to allow dectorists hunt there until I make it some day. She did say she's been asked quite a lot and caught people night hawking on the land because the property around her has given up a lot of crazy finds from rare gold coins, pot hoards and I think Viking jewerly was found nearby only a couple of years ago that made the news here? I guess fencing 70 plus acres is out of the question lol As crazy as it is in America right now it would be the perfect time for a peaceful vacation and my kids are grown and out their own. If I don't stop thinking about it I might make that trip this summer.
Could a simple metal detector be created by using an off the shelf cordless signal generator to drive the signal coil at 15.3 kHz and a low cost pocket oscilloscope connected to the detector coil to read the signal? Then just watch the scope signal visually.
I guess you are referring to the difference in "noisiness" of the signals. This has nothing to do with the phase by itself, just the signal strength. For objects that give a small signal (for example because they are small) you need to increase the gain in the experiment, which causes more noise in the result.
It is very informative. Thanks for preparing such a video. I want to have a sensitive metal detector, but they are expensive for me. I have a scope meter. I wonder if i can build a detector by making 2 coils for discrimination and using the scope meter as a detecting monitor. Then, connecting them to each other. Do you think it is possible? If so, could you please help me with the correct schematic? Thanks a lot.
Well, it's possible, but not practical. You need an oscillator as well. Better Google for schematics for a discriminating metal detector if you really want to build one yourself. Or buy a cheap entry level detector second hand to find out if metal detecting is even your thing. Hope this helps.
What you want to make is an oscillator using a capacitor and coil. You can watch this video on how to do that: ruclips.net/video/tjD9I95RAbw/видео.html
Nice information about Garrett AT Pro machine inner workings. Can you do a similar video about MineLabs Multi Frequency CTX3030? Thank You for the consideration of such a project.
It would be interesting to do, however unfortunately I don't have one at my disposal. As for the principle of the 3030, it also uses induction balancing (double D coil). However it does not use a single frequency like the Garrett AT pro but rather a range of frequencies between 1.5 and 100kHz. Because the inductive response of metals for each frequency is different, you can in principle have even better discrimination and identification then when using a single frequency. The frequency can also be optimized for a high depth range in a specific type of soil. With GPS and Wifi, all in all it is quite more advanced.
@@HuygensOptics Thank You, It is all that as you say, very complex for sure. I've had mine for 3 years now, it is a very sharp learning curve for sure. I keep learning about it every time I take it hunting on dry land or at the ocean beach. But, it goes very deep & tells me whats down there, I just have to listen to what it's telling me. lol Thank You again. Darrell
What's the ethics of metal detecting? Did you keep the wedding ring or sell it or did you make an effort to find the owner? I'd think finding the owner of the ring and making a good youtube video out of it has the potential to make a profit just as much as selling the ring would. I'm interested to know about this aspect.
One in a thousand people here give a toss about silver or brass, we're here for the gold, what ID is that? How reliable is discrimination with this unit? Those are the first two things we need to know.
This video has been discussed on hackaday. See hackaday.com/2019/11/26/progressive-or-thrash-how-metal-detectors-discriminate/#comments for more discussion on the subject.
People who want to make their own detectors sometimes ask us for the explanation of how it works. Now I know where to point them. Very good explanation, thanks a lot!
I've done some light research on this subject before and mostly came up with old schematics that I kinda gleaned were doing some kind of phase detection but with no explanation of the working principle of anything or how the coils interact. Great explanation and nothing beats a live demo with a scope to get some intuition of how the process works when it comes to these kind of things.
Ive been using detectors since the early 70s. With the early detecors you used a constant threshold and listening closely for the Phase Shift. The term we used was "Getting your ears right". After awhile you can mentally picture the graph and negative positive response curves in your head. Its was self inflicted Pavlonian Training.😂
THIS IS the BEST 🎉🎉🎉 description of coil operation on RUclips.
Certain old Whites Detectors could be precisely "dialed in" to do just that, but do it extremely well.
I’m an electrical engineer with a minor in electromagnetics. Excellent video! Wow! Thank you!!!
I realize this is 4 years old but wanted to comment anyway. WOW, just WOW. Thank you. As a new hobbyist this is great information and allows my mind to understand how my detector works. Truly appreciate the time and attention you took to make this amazing learning experience.
What's the age of the video got to do with anything 😂 people are so funny
@@ThePOSMwhat's the age of the video got to do with it? A lot of people don't respond back to old videos and some people don't even make them after years and move on from RUclips. I seldom get an answer back from the content creator on videos that are many years old
@jeanponce2017 you literally just said, what i said
my day job is building coils for MRI but I got interested in metal detectors after losing my phone in a lake and seeking to build one for the retrieval. In MRI, we overlap coils to cancel inductive coupling all the time. It's wonderful to see how this is applied to detecting metals, and knowledge of how different metals behave in a magnetic field made understanding the phase shift intuitive. Thanks for the great explanation!
I had a suspicion that this was how the double D worked. Thanks for testing it on video! great explanation overall as well.
Congratulations for this complete analysys of working of detectors . Very in deep and very good to understand , we appreciate your time and effort for this video . Thank you again
To better discriminate the Foucault currents (you call them eddy currents) you must use a third coil driven with 1 - 2 Hz signal, at pretty high intensity, 10 - 20 Ampere. This eliminates the need to move the coil assembly over the soil. Some used a neodimium magnet driven by a motor, but this produces a lot of interferences and the 2 Hz signal is hard to subtract in the signal processor.
A better way is to use two independent 19 KHz oscillators, and drive them so there is one 360 degree phase rotation per second of one oscillator with respect to the other. This make possible to measure the AL (permittivity / reluctance) and hysteresis separately. A modern 50 pence Cortex processor can do some stupendous tricks with the use of a FFT algorithm. I'm an analogue die-hard designer but I must admit that a good written code on a microprocessor seems to do miracles sometime. Enjoy the fun...
I just recently ran across and subbed your channel being an electronics guy interested in telescope optics. I use the sister machine with the AT Gold in California and Arizona. I call the detector an exercise machine getting me off into the wilds cleaning up bird shot and bullet fragments ;) It does indeed give fair indication of what denomination coin or pull tab will emerge. The ring find is a good lesson to dig each target and in time the aural attack will provide a sense that this pull tab is different. Wonderful channel!!!
This video is exactly what i was looking for. Ive studied electromagnetism in uni and highschool so i managed to grasp most of the science behind it. Thanks
One of the best explanations of how a Metal Detector works that I have found on RUclips.
I've been wanting to, and delaying, build a metal detector for years.
The biggest obstacle, not having an oscilloscope, was resolved a few years back, now I just need to start experimenting, and when I do decide to move my lazy ass and start working, I believe this video will be of great help.
Very interesting video! I believe this is the same effect used in shaded pole induction machines, which never made intuitive sense to me until now. They use a copper ring in the flux path of a single phase induction motor to create a weak additional phase to get the motor spinning (otherwise the magnetic field just alternates without spinning the motor).
I haven't seen a Tektronix scope in years. Excellent video and explanation, thank you.
I also still have a TDS220 , a workhorse and quite handy for plain measurements
Thank you, after going through so much bullshit I found what I was looking for.
I was always curious how these things could differentiate materials and your explanation satisfied my curiosity. I'm tempted to borrow a detector from a friend and give it a try sometime!
so far, the best explanation how detection work
This is just one method, there are a lot of different methods for metal detection
Well explained. Thank you for sharing.
This is the first time seeing Hilversum written. I heard the name first in a Van Morrison song "In the days before rock 'n' roll".
Excellent explanation! Thank you so much, it was very clear, I learnt a lot
Very interesting indeed, thanks for presenting this in such understanding way. Waiting for a similar explanation on pulse induction detectors.
I just recently started this hobby. This info helps a lot. My most exciting hunt starts today. My father just bought a new house just outside of historical Sackets Harbor. Metal detecting in the village is not aloud, but being his property is just outside the village, im good to go. Fingers crossed i find some really good finds.
Good luck, gernerally there is a reason why metal detecting is not allowed in certain places. There might be a lot to find, but it can also be because you are likely to dig up dead peope or dangerous stuff.
@@HuygensOptics ill be very careful in this endeavor. The historical significance is due to the war of 1812. The property is actually 2 miles north of the "battlefield". Im not an expert by any means, but after speaking to a few people that are, ive been told that the chances of finding any type of live ordinance will be pretty slim. I found out this morning that the original owners great grandfather was a blacksmith. Hes on his way over now to show me where they believe his shop was. The property is pretty big (in my opinion) at 12 acres and the original farmstead/house/shop is not where the current house sits. Ill let you know if anything exciting is found.
@@justaguyandhissilver4893 sounds exciting, good luck! I'm pretty sure you are up for a few nice finds.
Goedemiddag.
Thank you for this video its very informative. Have to admit i dont understand everything though. Bit frustrating because i realy badly want to understand it. I recently built a PI metal detector using 3d printed parts , it works ok using a colpitts ocilator and arduino. It works well enough
to find the pipes in my house walls, but the metal has to be about the same length as the coil before it will detect it about 20cm , smaller objects has to litrally enter the center of the coil. The theory and methods behind metal detection has become an obsession 😀. Groete from a fellow afrikaner dutch descendant. Goeie werk en hou so aan! Lekker!
Hello Martin, So the video is about VLF-technology (Very Low Frequency), PI detectors work on a different principle as you likely know. I also build a PI detection setup and, like you, found that it is actually not that easy to achieve a high sensitivity. Also, evaluation of the rise and decay in the magnetic induction caused by the pulse was not as easy as just examining the phase shift observed with VLF, so discrimination is hard. If you are digging for gold in an iron-rich ground, PI is the technology to use, but even then you need all kinds of tricks to filter out the signal from the noise if you want to go deep. Here in the Netherlands most PI detectors are not very usefull, because of the generally limited dicrimination between treasure and trash. So that is why I don't own one. Good luck detecting! Cheers, Jeroen
Someone needs to make a open-source high end metal detector, some amazing stuff could be done, I'm imagining a system with GPS and accelerometers that could produce "maps" of underground responses, and with fpga signal processing I'm sure that it would be possible to do some incredible discrimination.
Just purchase the Minelab CTX-3030 if you want to GPS map your finds.
@@SeattleRingHunter Keyword: Open Source
Being a retired pipeline excavator, I can only imagine how valuable a map of underground fixtures, utilities, etc., is going to be to future generations of hoehand s...
Very interesting!
Nice video, curious as to why gold was left out. Would be interested in the science behind why gold and aluminum ring up similarly, and if there is a way to potentially distinguish between the two with a detector.
In principle it is possible to distinguish between the two, gold is diamagnetic whereas aluminium is paramagnetic. They have approx. the same conductivity, and this will be the mayor contribution to the phase shift in VLF detection. An advanced PI (pulse induction) detector should be able to detect the difference between the two materials.
highly informative, thank you!! Now I'm thinking about building my own since I have access to some motor wire and an oscilliscope
I recently purchased a late model surplus military detector that will pick up the very small particulate metal that is found in plastic explosives. It will detect metal that is literally as small as a single grain of sand, and it will do this at considerable distances away from the search coil. Presumably it does this based on the same principle of physics that is described in this well made video. However, i'm curious to know if the coil on this machine is considerably different on this detector or if the electronics in the control head account for this extreme sensitivity to a nearly invisible amount of metal. It doesn't seem possible that a detector could pick up the extremely tiny amounts of metal that this thing will, yet somehow it does this very easily. Great video!
Perfectly explained and presented. Nice and Like
Excellent video and very nice experiments. Please allow me however to express some doubts about the interpretation: I don't think that diamagnetism or paramagnetism play any role at all: they are both extremely weak effects with susceptibilities in the 10^-4 range. Moreover, many non-metals are diamagnetic and/or paramagnetic and do not give any response to a metal detector. My understanding is that the phase shift is mostly determined by the decay time of the eddy currents in the object, which is given by L/R, the ratio of the inductance to the resistance of the object. Thick silver/copper/aluminium objects have an L/R of order 100 microseconds, while iron or aluminum foil have L/R of less than 10microseconds. Compare these to the period of the 15kHz emission, and you get the high L/R giving a lagging disturbance with a big phase shift and the low L/R an immediate disturbance with little phase shift.
I agree that the main detection mechanism for most metal detectors is based on conduction and eddy currents. However, conductivity alone cannot explain the differences in phase shift between metals. I'm not sure to which non-metals you refer, but conductivity is not always required for detection with a metal detector. Take ferrite: non conductive, paramagnetic and it gives a huge signal. Not all metal detectors will see it though, due to discrimination settings.
@@HuygensOptics I was thinking of liquid oxygen, but actually that's an exceptional case, there are indeed very few non-metallic paramagnetic materials. On the other hand, every material is diamagnetic. Ferrite is ferromagnetic and ferromagnetism completely overwhelms paramagnetism if present. My understanding is that only conduction and ferromagnetism give a response in metal detectors, with conduction giving a phase shift between 0 and 180 degrees (twice the phase shift of the equivalent LR circuit) and ferromagnetism contributes with 0 phase shift (if it is instantaneous compared to the timescale of the oscillating field - but I'm not sure about the latter..)
@@rgco2266 that is correct, ferrite shows 0 phase shift (or very close to that value), as is also shown in the video. In the standard detection modes of the Garrett it is not always detected due to this exceptional behaviour. However, in the "pinpoint mode", it is always detected very strongly because only signal is considered and phase is ignored. Thanks for the additional information you supplied.
TOP Video eindelijk een goede en duidelijke uitleg. En een helehoop bij geleerd ik moet het dus sneller bewegen. Als je films ziet waar sommige met dat ding als een malle tekeer gaan denk je uitslovers maar het blijkt dat het zo moet.. lol.. Met die spoelen was het gene ik beter wilde begrijpen en dat hebt u super duidelijk uitgelegt. Ik heb net een week een detector een MD-3010ii uit china dacht eenk kijken of ik dit leuk vindt. Maar hij werkt niet naar behoren en wat blijkt er is iets met een spoel die niet werkt. Er zit een stekker met 5 pins in 2x2 voor spoelen en een vrij. Alleen hebben ze een kabel verkeerd geslodeerd en een zou dan niet moeten werken. Hoewel hij wel iets doet als ik over metaal ga en ook de PP (pinpoint) werkt ook fijtloos dus ben ik op zoek naar het antwoord hoe zit het nu. Op de printplaat komen 4 kabels aan dus ik dacht 2 voor elke spoel en met die gedachten zou hij dan niet kunnen werken of zit ik helemaal fout??
Groeten, Andre
ABSOLUTE BEST metal detector explanation! ...but of course 😀
Why did you exclude gold and platinum from your examples?
Great presentation. Interesting point for what ever reason gold was omitted from your list of metals. Being that gold is one of the most desired treasure metals we detect for. Would have been nice to compare the conductivity of silver verses gold on your list. Cheers, #SeattleRingHunter
Fantastic video. Thanks for the insight.
This is my kinda cake.... LOVE IT!!
Well done *SIR*
Learned alot and amazed in how much i had wrong on the principle.
Especialy that there s one recepteror coil and one transmitting .
i was under the impression that the two coils alternate between beying a receptor and emmitor coil .
thanks for clearing that one out .
I had a garret detector , nowerday i hunt inland with XP DEUS and on salty beaches with an Minelab equinox 800 .
Would love to see you analyze the FBS method they use , sending 5 different frequencys at once and eliminating all interferrence with the metalions present in salt.
would love to loan my minelab detector , so you zouldn't have to buy one ;)
these are topics i litrteraly lay awake of at night , as i dream of making my own metaldetector ..one day
greetings from Zeeuws Vlaanderen hihi
Johny Geerts
Fascinating explanation....cheers.
Great little metal detector.
¡Magnífico video y muchas gracias por compartir... Saludos desde Pátzcuaro Méx.!
You explained well, but I was surprised that gold was not among the metals that were tested. Please explain how much gold is known according to your experience.
Metal detecting, the ultimate hobby of old men, which is why I’m watching this video.
Indication: probably in older models changing emitter and phased indication to square wave and operation amplifier substraction stage followed by accumulator operation amplifier stage which output is between 0 V to DC positive and 0 V = 180° shift indication would be scored as indicative ID 100.
Beautifully explained! Thank you!
Huge respect. Sir
Great video. Thank you!
Beitifull!! Remember the pinpoint does not use a trigger..
It would be nice if you would use xy display mode on the oscilloscope.
New comments on an old post are unlikely to be detected, but I wonder if a double-D detector could be used to find sunken submarines or crashed airplanes. The search coils could be huge, perhaps 10 meters, and the frequency could be very low, perhaps 100 Hz in order to penetrate seawater. Several issues would be if the detector sensitivity could match a SQUID or MAD magnetometer, and how big the search cone would be.
That's good work
Excellent video
Thanks very useful for me
Have you thought about studying the shape and style of coil on the performance of detection, by making micro coils for the detector? Say ,50-75mm coils? I had the idea of using two pancake serpentine coils have one zig while the other zags! Alternating the coil around ,8 x 20 mm dowels, bone coul is on the outside of the dowel with the other on the inside! So each dowel is like a small DD coil, this could boost performance especially with a large 1000mm boil with the use of 100mm dowels! So there is basically 8 x100 mm coils. Could this be effective??
Part of the power of the DD coil is that it allows you to better locate an object during scanning it over the ground sideways. You would miss that feature if you were to create multiple small coils and add them together in a single coil.
Is there some kind of accelerometer to detect whether you are sweeping L-->R or R -->L ?
I can imagine that with a single Tx and single Rx coil, for the same sweep-direction, you would get an opposite polarity for (say) aluminium vs. steel. Am I missing sth here?
very satisfying explication good job
Very informative video. The question I have is what is the uH value of the second coil ? In advance many thanks
I did not measure it, however it's quite high. Where the transmission coil only has 10-20 windings, the reception coil can have many hundreds of windings. If I think of it in the coming days, I will try to measure the actual value.
@@HuygensOptics hola buena noche quisiera saber si puedo conectar bobina doble d a detector pirata ruso
@@HuygensOptics hola buena noche te quería pregunta de la bobina doble d tiene dos cables vivo y dos negativo
@@robertonazarenofrias3500 why the broken Spanish?? xDDD
@@Ktulu789 hola buen dia amigo quisiera saber si tene el lista de los componentes electrónicos del detector de metales terminator 3 el que tiene 7 imtegrados de catorce pata y un integrado de 8 pata
Anyone knows what's the name of the particular coil at 5:35 ? This is a really heplful and well made video about the working principle of a metal detecting device. Thank you very much.
Excellent ❤❤❤
great video thank you
Thank you, hard to understand for me but interesting. Do you know what happens when you adjust the disc higher on the machine? Because it influences the detection depth if you ad more discrimination to the machine.
I'm not sure, I think increasing the discrimination will generally lead to lower detection sensitivity. But with the detector I own I can only set rejection of specific target ID-ranges, not a general discrimination level.
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Do these electrical Eddy-currents propagate in the same way as thermodynamic Eddy-currents?
Wow, that's very interesting. Thank you for sharing.
Can items avoid detection if you place them inside a faraday cage?
Great information.You have another subcriber .Your channel subjects great
It is very interesting test :D May I ask: what are those wire spec of measurement coils (R of coil, wire Φ, Turns of coil)?
Hello friend I live here in the country Brazil, How to make a coil for metal detector quest x5? I tried to make sticks instead but I couldn't. Thanks
Dag
Are there metal detectors that can work statically? without transient?
What is the part number of the receiver coil you are using?
so useful & informative. could you explain long range locators as well plz ?
No point. They don't work.
Hello..Does the Admiral device detect natural gold nuggets?
0:17 Oh I have found one of those before!
Thanks!
Good
Can its id similar to nokta impact
Great video and thanks for taking the time and effort to set it all up. The results really correlate with my metal detecting IDs (Minelab Equinox) but I wish you'd included copper as that's such a commonly found metal. I suppose being a good conductor and diamagnetic it'll be similar to silver?
Your equinox runs using 2 separate frequencies simultaneously. The lower frequency is more sensitive to copper and silver it targets higher up the VDI scale where as the higher frequency is more sensitive to the lower frequency. The two frequencies have a huge difference in the shift of the targets phase. When it detects a target it reads the low frequencies shift and strength of the signal. Then it does the same with the high frequency. There is a processor that calculates the difference between the two and assigns it a VDI (visual target identification) and generally it is pretty accurate but it doesn't "suggest" one type of a target over the other. The Whites DFX operates sort of the same BUT it has a feature which allows you to read the shift in the phase which damn near tells you exactly what it is which a much higher degree of accuracy. I'll give you an example. If the VDI reads 20 - 22 it is could be a nickel or a pulltab. When the DC Phase shift is turned on you squeeze a trigger and pinpoint it. If its a nickel the DC Phase will read 39 -42 +/- depending on ground minerals. If the DC Phase reads in the mid 60's to low 70's its a piece of modern aluminum. If its really low like in the teens its old aluminum. Its amazingly accurate once you remember what the targets phase read. But before that I would already know its a nickel because there is a bar graft from 1 to 4 bars. Aluminum will give 1 bar maybe 2 if its a bigger piece. The nickel will run to the top and stack all 4 bars or maybe 3 if its deep. Now if it stacks 4 bars but the DC Phase hits the 50's to 60's you may want to call it a pull tab with the high DC Phase but being it stacked 4 bars and not 1 it is a nickel between 1942-1945 because its a war nickel that have a percentage of silver in it so between the VDI, the DC Phase and the bar graph that Whites calls it the signagraph those 3 points of ID can tell you everything about the coin but the date. And still in the case of war nickels it zero's that down to a few years. VDI of high 60's with DC Phase of 67 to 72 is a penny from 1982 until present. If the VDI hit the upper 70's and the DC Phase is in the high 70's its a copper penny from 1982 and earlier. In '82 both designs were made half way through the season to save copper and instead made it from zinc then cladded it with copper. If the copper plate is intact those numbers above are correct. If it starts to bubble or corrode then the numbers drop very fast on the DC Phase reading. My friends refused to bet me even 1 dime anymore on calling the targets before I dig. The very last time I bet with 2 of my buddies who swept their detectors over it, one calling it a screw cap and the other called it piece of aluminum or a foil ball its a non dig but I called it a penny and to dig it they jumped on that bet in a second Then showing off a little I said its going to be a penny from 1982 or newer it's a "zincoln" the nickname for the zinc pennys and a penny with bubbles popping off the surface dated 1995 came out they were stunned on how I called it right on a clear non penny signal. It was the detector and the 3 points of ID that made that one of the best detectors ever for its time. It had so many settings that new hunters didn't understand and they could adjust it and cause it to lose depth until you learned it and since people had hard enough time coughing up $1,200 for a detector they wanted to be able to turn it on and go. And though it had factory presets for learners the power level was set in the high 60's so people naturally cranked it up higher without changing other setting and all it did was chatter. Whites omitted some features, made it more learner friendly and it became the V3i. That machine runs 3 frequencies and even shows you which frequency is dominate which gives you a hint right their if its a coin or not. But they have come a long way. They also use concentric coils not DD's which can detect deeper but they also see more trash and minerals around the target. The Equinox 800 is a pretty good detector to so you'll do well with it. One tip for all its worth in heavy iron or black sand power down just a bit. It barely loses sensitivity or depth but it greatly cuts down on the noisy chatter. Detectors rarely can handle cranking it to the max without falsing. Good Luck hunting
Also if you want to learn a trick. Sweep over a pulltab and read the ID. Then cut that same pull tab and straighten it out. Now its the same piece, same metal content, same mass (volume of metal) but what is it reading now? And why???
@@stevenallen9592 Thanks for the very detailed and in-depth replies! I'm guessing with all your talk of nickel you're on the wrong side of the Atlantic to be digging up Medieval or Roman coins. That's interesting about the White's detector - but in practice although it's fun to predict what you're about to dig, how often do you (unless it's iron) actuually say nope, not digging that. With the Nox 800 if I dug only 4-7 (cut hammered quarters), 8-10 (cut halves), 12 (hammered pennies) and 21-22 (milled coins) I'd probably recover over 95% of what I keep without digging up all the other crap. Below 4, 11 and 13-17 are nearly always rubbish (I include buttons and musket balls as rubbbish). Over 21 is usually large copper or aluminium. But a large hammered coin such as a shilling will ring at around 18 or higher, Roman coind perhaps 14-18, artefacts such as Roman brooches could be anything, gold can be low ID, so I dig a lot of crap despite those items being very uncommon. So I dig a lot of crap knowing I'm about to dig crap just in case it isn''t crap!
I started detecting in the 1970s with C-Scope VLF machines. They had no ID, just an analogue meter at best. There were two knobs - volume and discrimination and there was a reset button for ground balance. I remember though I could discriminate quite accurately by the consonants of the tones. Coins tended to have a softer edge whereas iron or lead had hard edges. It's similar with the Nox but not as obvious or intuitive. But watching Holzhammer Sagas RUclips channel I think the Deus in Lite mode has similar qualities. I wonder if there's still a place for those old analogue detectors but with better deeper coils. My 22 year old BMW car runs just fine without reverse camera, lane tracking, telling me when to change gear etc. Similarly I wonder if all the software embedded in these detectors i really necessary
@@stefkuna
I re read what I posted to remember what the topic was and I caught a bad typo where I wrote the higher frequency is more sensitive to the lower frequencies lol. I probably wrote that apply late at night half a sleep. It wouldn't the my first time. I meant th3 higher frequencies like the lower VDI targets. I'm familiar with the "NOX" in the sense of its dual frequencies and iron cancellation and other features but I haven't used one so I don't know where what targets ID at. I was trying to make a point how those targets that have the same VDI or ID number range like American Nickels reading the same as some gold rings or even aluminum. When using a multi frequency detector the computer tries to determine which frequency is responding better and leans towards the ID of that frequency scale. Air testing doesn't take in account the fact there's no minerals or trash involved with the signal or its ID. I'm a little familiar with the difference in the soil in England as opposed to North America especially in the original colonial states. There's actually been a few hammered silvers pop up but its thought that someone had them collecting and it got lost centuries later as opposed to their when its lost not long after being struck. Being as old as you area is you've built up centuries of metal and of coarse the worst being iron. You also have that hit ground they call coke, right? We have spots of it but its not plowed everywhere its from native American fire pits because much of it is actually organic material mostly charred wood from fire pits. Then over the years this "coke" is plowed all over, rain spreader some and some areas of older pits that were deep is really bad. The lower frequency which is more sensitive on thicker silver or copper coins don't hit those very deep because of that hot soil and can miss those little hammered silver or small gold. Then the higher frequency with chatters a little more is better on seeing those tiny silvers that the lower frequency struggles with because of the tough ground but it loses depth on coppers. The detector also gets thrown off by the ground reading. You might balance it and track on it but the value of the ground changes a little more erratically because its not a metal that creates a magnetic response more as it silences it like a ferrite rod. Nothing here even the few hot spot burn pits are enough to deal with like you deal with. But another point that I really wanted to bring up was the shift in the phase. The microprocessor can figure out which frequency is responding better and do its calculations but having that control of knowing the difference between the phase on two targets with the same VDI make for an extremely accurate ID. I used to talk to a guy named Jimmy "Sierra" Normandy. He worked with Whites and helped the development of several detectors starti,g with gold. He told the nickname Jimmy Sierra because he was/is a gold prospector in the Sierra mountains in California. I picked his brain apart to learn these settings on the DFX. He used to field test for Whites in England and he started these paid detecting hunts where about 10 or 12 guys paid at that time (2006+/-) around $2,000 US dollars and the money went to a farmer over there to hunt fields that have produced hoards in the past. On 2008 I almost went if it weren't for the conditions. The farmer got paid to rent the land AND a cut of the value of the find. That I was OK with. Then everything found had to stay for months for the government to go through it, decide if they want it, take a cut if the laws there required it. Then either bought them and paid what they call fair value or set the value and took their cut. Then if they didn't keep the common stuff the contact there mailed the finds minus what the government took and what deal you make with the owner paying him the money or a share of the coins at his call. Ugh and even that I said well that's how it goes. What I didn't like was that a person who spent years to get pretty good could hit some valuable finds and a guy who goes just to see the country side and maybe not hunt much gets to get an equal share of what's found even if they found nothing. That didn't sit well when I heard from people who attended these hunts before that some guys who are wealthy would go and good around in hopes one of the hunters hit something valuable and he gets as much as the guy who dug it? The DFX didn't go over well there because it takes time to really know what its doing when you adjust the sweep speed, or the track speed, inhibit it from tracking and manually track etc etc etc. It was not a new owner friendly unless you spent a long time and had a lot of patience. I think Minelabs popular there. The Deus even some Makro's are preferred detectors there. You know what's more popular there then I would. Jimmy told me a tip about hunting with fresh plowed ground after its rolled and it rained. After the rain the coke leaves s film on the top of the ground. He said to walk through it dragging your foot and break up that film because it acts like shielding does in a coil and the detector was more stable by breaking that later if coke. It makes sense to me being it allows the magnetic field to go down with less interference. One day I'm going to go on a hunt there. I have a half sister that lives there. My dad met an English woman during the war and her mother didn't come to the states when my father was withdrawn after the war. I've met her being she would come to the states on and off but she's kept the land her families owned for a long time. I specifically asked her, (it was more like I begged her lol) not to allow dectorists hunt there until I make it some day. She did say she's been asked quite a lot and caught people night hawking on the land because the property around her has given up a lot of crazy finds from rare gold coins, pot hoards and I think Viking jewerly was found nearby only a couple of years ago that made the news here? I guess fencing 70 plus acres is out of the question lol As crazy as it is in America right now it would be the perfect time for a peaceful vacation and my kids are grown and out their own. If I don't stop thinking about it I might make that trip this summer.
Beautiful
Could a simple metal detector be created by using an off the shelf cordless signal generator to drive the signal coil at 15.3 kHz and a low cost pocket oscilloscope connected to the detector coil to read the signal? Then just watch the scope signal visually.
Yes I guess it is possible though it would be a bit of a cumbersome and expensive solution
Question , does the phase shift lines matter? in fine tuning accuracy & discrimination . The sine wave being staticky and spikey verse smooth
I guess you are referring to the difference in "noisiness" of the signals. This has nothing to do with the phase by itself, just the signal strength. For objects that give a small signal (for example because they are small) you need to increase the gain in the experiment, which causes more noise in the result.
would gold register in the Iron range or higher?
♥♥♥
What is the value of your test pickup coils, 2.5mH ? #SeattleRingHunter
It is very informative. Thanks for preparing such a video.
I want to have a sensitive metal detector, but they are expensive for me. I have a scope meter. I wonder if i can build a detector by making 2 coils for discrimination and using the scope meter as a detecting monitor. Then, connecting them to each other. Do you think it is possible? If so, could you please help me with the correct schematic?
Thanks a lot.
Well, it's possible, but not practical. You need an oscillator as well. Better Google for schematics for a discriminating metal detector if you really want to build one yourself. Or buy a cheap entry level detector second hand to find out if metal detecting is even your thing. Hope this helps.
@@HuygensOptics Thank you for your help. You've shown me the way.
Bro, gonna make a metal detector, open-source it, and bankrupt the companies, brb! Thanks for the vid!
Hi I want to broadcast vlf waves from a few yards, so how is the calculation? (Coil count) (voltage) (ohm)
What you want to make is an oscillator using a capacitor and coil. You can watch this video on how to do that: ruclips.net/video/tjD9I95RAbw/видео.html
this type of discrimination is atrocious and needs to be dealt with harshly.
Nice information about Garrett AT Pro machine inner workings.
Can you do a similar video about MineLabs Multi Frequency CTX3030?
Thank You for the consideration of such a project.
It would be interesting to do, however unfortunately I don't have one at my disposal. As for the principle of the 3030, it also uses induction balancing (double D coil). However it does not use a single frequency like the Garrett AT pro but rather a range of frequencies between 1.5 and 100kHz. Because the inductive response of metals for each frequency is different, you can in principle have even better discrimination and identification then when using a single frequency. The frequency can also be optimized for a high depth range in a specific type of soil. With GPS and Wifi, all in all it is quite more advanced.
@@HuygensOptics Thank You, It is all that as you say, very complex for sure. I've had mine for 3 years now, it is a very sharp learning curve for sure. I keep learning about it every time I take it hunting on dry land or at the ocean beach. But, it goes very deep & tells me whats down there, I just have to listen to what it's telling me. lol Thank You again. Darrell
Here in America there's also a lot of junk metal in the ground
Were the condoms past their use by date? I love your humour. Thanks for your videos.
What's the ethics of metal detecting? Did you keep the wedding ring or sell it or did you make an effort to find the owner? I'd think finding the owner of the ring and making a good youtube video out of it has the potential to make a profit just as much as selling the ring would. I'm interested to know about this aspect.
The owner was found through a Facebook post within 24 hours using the names engraved in the ring and was then returned to him.
Ukuran kabel TX nya berapa??
Ukuran kabel RX nya berapa??
Nerdy!
Poderia ser legendado em Inglês Espanhol ou Português
Valeu obrigado
Those double-D gold diggers are a mixed blessing....
What is id for gold
Depending on size it is somewhere between 60-70
يعطيك العافي بعتلي صورت المخطت لو سمحت
I sent you an email, thank you....Hanus
Should have tested a superconductor.
I do NOT want to dig up a grenade!!!!!!!😱😱😱😱😱
You neglected gold response?...
One in a thousand people here give a toss about silver or brass, we're here for the gold, what ID is that? How reliable is discrimination with this unit? Those are the first two things we need to know.
It depends on the size, small items like coins or rings between 60-70. Steering only on ID is completely unreliable for discriminating for gold.