After watching this video I got a notification: "Your shoplifting skill increased to 21!" Nice.

Your use of the CD tracks to measure the movement was brilliant! I loved that. Great video overall, although I would have liked at least one close-up shot of the strips near the beginning. I'm sure they're basically featureless, but when you first took them out and were handling them I found myself wishing you would show a good macro shot of them.

Wow this looks fantastic. One tip, when demonstrating objects as small as these, a closer camera angle would be great!

The lever solution is genius

Nice opening shot. Very clean. But I like seeing a messy lab in the background just as much. I watch because it's about the science. And I have always been curious. Will have to re-activate one of thee things and take it through a store to try this out!

All my young years in retail I always wondered how those tags worked. Thanks Ben! Love the new lab diggs too... :-)

I always cut the tags open and save the loose metal strips, as they're perfect for shimming lock cylinders for rekeying.

great video and analysis. love the spring jig.

Fascinating as always, Ben! I never knew how those strips worked (and I admit to opening them up to see what was inside). You gotta love all of the uses for Kapton tape...

Some anti-theft tags use an amorphous ribbon with a very square B-H loop and a very low coercivity, in fact the earths magnetic field is strong enough to magnetize them in one direction or the other. The transmitter coil generates a pair of fields at two different frequencies and the amorphous ribbon acts as a non-linear magnetic mixer generating fields at the sum and difference frequencies. Say the transmitter generates 5kHz and 8kHz then the sum and difference will be 13kHz and 3kHz respectively. The receiver coils pick up the 13kHz and sound the alarm. To deactivate the tags a small piece of steel adjacent to the ribbon is magnetised and that keeps the ribbon saturated.

Thanks! I really love your detailed explanations of stuff. I've watched your most recent videos since subscribing about 6 months ago, but still catching up on this older content. So, so nice and thorough. It isn't flashy or anything, just very clear explanations. Please keep it up.

I guess I always assumed these were some kind of primitive RFID tag and never thought about it. Very interesting!

The level of scientific intuition here is amazing, how you choose the right methods to investigate and validate set assumptions. Thumbs up!

Love the new setup, and I really love the quality content you're putting out. I check for updates daily and slightly bummed when there's non, but never disappointed by what you put out when you do upload something new :)

Wow your new lighting looks so pro!

Wow - These videos make me so happy! I studied electronics, electrical and telecommunications engineer for 10 years and you bring several concepts together in a very simple and beutiful way, like different sounds in a orchestra. Amazing!!! Congrats!

Beautiful work (as always). MANY thanks for taking the time and trouble to research this topic, construct the apparatus, eliminate the bugs, record the video, edit and post it.

Your production quality is some of the best on KZfaq, if not the best. Good work, great lesson.

Amazing video! I love your ingenuity in the testing setups. I learned a lot!

you just keep going deeper and deeper into it...some of the topics you explain in detail and some other you brush off... overall it's amazing... and like your original intentions, these videos motivate me to try my own experiments....

Even though I don't understand half of what you're talking about, you present your findings in such a way that keeps me watching. Thank you for keeping me interested ;-)

This guy is clever! This channel is one of the most high level in the internet! Congratulations for this incredible work!

Great content as always. Sound and lighting are greatly improved - nice job there too!

Very, very good video! Your test and observation methods are very creative! Thanks for your hard work and video!

Yes! I immediately noticed the upgrades! So good to see you are making it :D

That was totally awesome !! Never seen any object move such a minute distance ever and with just bits and pieces.to demonstrate it.Fantastic!!

+Applied Science, you're always answering the questions I didn't know that I wanted to ask! Thank you so much for your videos! I can't get enough of them!

I just want to let you know that here in 2022, I am re-watching all of your content for probably the third time. Your videos could be 3 hours long and I would still be dismayed when they're over.

Glad to see your video equipment improving, but more importantly I'm glad to see youre happy about it :)

I've wanted to know this for a couple of years now, I've really wondered how these works.. Wow, Thanks for taking your time to investigate and share the results with us! =D Great video!

Excellent video! Love the improvements! A very interesting topic.

Thank you for making these videos with so much care, I highly appreciate that you explain things so deeply! The video qualuty is also very good. Next improvement could be more close ups, I would like to see the small piece of metal, the graph and your measuring apparatus in more detail. If you have enough time to edit :)

I wish all youtube channels had this good sound!. Nice work, and informative video as always :)

This is very cool and I appreciate you doing original research to investigate it. This is why I started watching KZfaq

Very thorough investigation! Those things are actually pretty ingenious, I'm impressed.

This is exactly the detailed explanation I was hoping for, thanks!

Fun and informative experiment! This was really fun to watch you do. I had a good chuckle when you mentioned over-magnetizing one of the strips. Gotta experiment to learn. :D

You are so cool Ben. I'm a computer engineer of '14 and I wish I could be a quarter as awesome as these videos. Your projects are inspiring.

Great, intelligent video! Thank you for increasing the quality of KZfaq!

Thanks for the videos! Congrats on the new setup, but as someone else pointed out, I am here for the science.

This is amazing! You've expose the beauty of the everyday. Thank you!

In the first minute you may think it;s not interesting, But you MUST SEE the complete lengh of the video,!! This guy is amazing, in his complete setup, Great setup and a great Research, Thanks for sharing !!!

Thank you for being a great teacher. I learn a lot of things on this channel ! Brilliant apparatus, btw

These videos are so fun to watch. Oh, and informative, too.

How in the world have I never found this channel before!? This is great!

Very interesting, I especially like the meter you made to measure such slight movements. I use the strips as shims in my home machine shop, because their thickness is between .0005 to .001, for example; when I have one of my lathes preoccupied with a four jaw set up, that I can't break down, I'll use another lathe that has a three jaw chuck, test run out with a workpiece in the jaws, and fill the high spots with two or three of those strips, to get as close to a four jaw reading, if at, times, even better. I was commissioned to build a micro wire straightener 2. Years ago, and, as you may know, the straightener parts had to mesh as perfect as a Swiss watch, suffice it to say, I placed at least ten of those strips through the machine, and when their assessor tested the little machine he certified it as passing, as a Swiss watch, not knowing of the security strips turned shims...rotfl 😃

Hi Ben; Many years ago, mid '80s, ASIR, I had a magnitostrictive delay line. It was from a mid '60s Friden calculator. Unfortunately I have lost track of it now. This had a long steel wire carefully supported and coiled into a spiral. The transducers at each end had 2 tiny strips of the magnetostrictive material spot welded to the wire at right angles. There was a small coil around one of the strips and a small bias magnet in the coil. Both ends were made the same. When I pulsed the coil it would cause one strip to lengthan and the other to shrink. This applied a twist to the wore which propagated down the wire. Of course, at the other end the strips were forced to stretch and shrink inducing a magnetic field in the coil. You could easily see the delayed signal on a 'scope. I speculated that it could dynamically hold about 8k bits of data. Maybe more, probably less. I didn't have a micro yet so couldn't actually see if I could recirculate any data through it. I have there been any amateur attempts at making such a device? redrok redrok.com

Another great video! The curve of magnetic field vs mechanical output is the same as magnetic field vs recorded signal for audiotape. Tape recorders apply bias to the recorded signal to move the recordings into the linear portion of the curve. Some cheap cassette recorders use a magnet for DC bias, but most use AC bias around 45 khz.

When i see titles of your video, i have no idea what it is about. But the moment i start playing, i m lost. Thanx Ben, keep videos coming.

And suddenly I spent a whole evening rewatching your videos. Much better than some silly discovery documentary ☺ Great videos.

Thank you for such a detailed explanation with excellent visualization

Great Video ! keep it up with the good work, i liked a lot of the solution you have found to mesure the dilation

Hi Ben. Thanks for the video, it was enjoyable as always. If your still interested in this topic you may want to try using a strain gauge to estimate the saturation magnetostriction. If you glue the strain gauge directly to the ribbon surface with any brand of cyanoacrylate and then monitor the change in resistance via a wheatstone bridge configuration while slowly rotating the sample/applied field you can quite accurately estimate the saturation magnetostriction using the know gauge factor. We use this method in the lab I work in and so I can assure you its possible to achieve sub ppm resolution. I wish I could point you in the direction of a few papers on the topic but its very poorly documented in the literature. If you have any questions about this, or on magnetic materials (especially nanocrystalline or amorphous materials) in general feel free to drop me a line. Richard

Your data suggests that the resonant frequency of the metal strip is narrowly defined by the dimensions and temperature. If you were to change the temperature significantly, you'd change the resonant frequency and thus the tag would fail to function normally.

Wow. The determination to measure it 👍🏻👍🏻 huge props.

Fascinating video. I often wondered how this sort of tag worked. Of course everyone now knows how to defeat them. Like the upgrades.

Great video! A quick note: While the maximum displacement under static field might be ~several microns, that is only under static field. Fluctuating the field at the resonant frequency of the metal plate will "ring the bell" and cause greater and greater displacements

The whole explanation showing the expansion is great.

He scienced the shit out of that.

@6:06 this piece is called the "Bias Magnet" and it provides the Magnetic Bias to put the resonating Magnetorestrictive thin metal on the resonating point on the curve. If the magnet is not present (Deactivated Tag) then the Magnetorestrictive piece of metal is still the same but will be displaced to a non resonating state on the curve.

Thank you for an excellent experiment! Well done!

Nice practical experiment setup!

love your detailed videos, explaining every-day physics!

These videos are just awesome & hope u keep making them

first time i have seen one of your video's. very very informative, have wondered for a long time exactly how those tags worked, now i know. keep up the good work, please ignore the slackers / idiots / thief's . i have subscribed.

You are a really, really good presenter! Awesome presentation!

good video.. very detailed explanation.. clearly you have put in a lot of effort in making this video.. I appreciate your work..

Definitely true. That was a brilliant way of describing the anti theft device and a way to measure its movement. However even in it's simplicity, I don't think too many understood it. Great demonstration.:-)

In my university library, you could easily locate the location of the magnetic field if you walked through with headphones on. Very high pitched, probably around 15kHz in my case.

Good and informative as always. Keep it up!

excellent explanation and demonstration!

Thank you for making such a wonderful video . It cleared lots of doubt.

Great video!, I've always wondered about these. Still waiting for HL3 though :(

Fascinating, thanks Ben!

It doesn't matter which is the subject, this guy makes an amazing video and explanation.

Great visualisation with lever and microscpoe!

dude ur amazing just dnt stop i know my generation is not interested in science and u deserve more i learned on ur channel compared to school . ur the best just keep it up.

I have always wondered about these. Thanks!

Excellent method for showing the change in length!

5:26 The funny thing is: They are going for the inductor-cap combo a lot of the times, but they make it out of aluminium foil and between two plastic/canvas sheets and that's it. It's working, it's flexible and it's way cheaper than even these metal strips. It's just some spiral shape with the ends folded over each other while keeping those insulated to form the inductor and capacitor.

thanks for explaining magnetostriction, very clear and concisely! just noting that this is the most common tags used in retail. there are others, like the square ones with the metallic spiral. most made in China products will use the cheaper strip

Great work, as always!

Brilliant work as always!

I'm sure you diagrams and scope screens are clearly visible to you Ben, but could you Zoom in so viewers aren't struggling to see what amounts to 1/16th of OUR viewing screen size?

I Really enjoy your channel, I just wish I could understand what your doing. Most of what you do is way over my head, but I'll figure it out one day and your videos help!

the experimental setup was awesome

You look so happy with your new setup :)

You make fantastic videos. Keep up the good work.

Now this is a VERY in depth video on how the magnet strips work

Really cool! I have always wondered how those things workes when I see them (the tags are so small that it would be hard to put any electronics in them, haha), but have forgot to do any reseach.

Your video are quite impressive. Keep up with this highly informative channel 👍👍👍

Don’t let let ben fool you, *he’s so committed to accuracy he actually committed many counts of grand larceny just to get active tags for us*

One thing you forget to consider is that under the 58kHz excitation, the strip is resonating. The amplitude of displacement is roughly Q times the displacement under static (DC) excitation. Here Q is the quality factor of the resonator. From the ring down, Q is not small (most certainly more than 100, possibly more than 1000). So in the end, it is indeed theoretically possible for the strip to develop 0.1% strain (1/1000 inch over 1 inch) at its resonance frequency (12 ppm * 100 = 0.12%). These being said, the lever setup is quite neat for static test!

Thank you for such an enlightening video! Technical details on AM tags do not abound in the web. A hug from Argentina.

I can't believe the people who disliked your great video. I can only assume that those were the ones who wanted you to tell them how to defeat the anti-theft tags and have no science background to figure it out themselves.

I will apply this knowledge to my future shoplifting endeavours. Thank you.

My understanding was that the use of a strong magnet would saturate the adjacent hard steel where its coercivity would leave it in a permanent magnet state that was just right for generating the ring-down pulse. To deactivate you had to de-magneitze the hard steel strip, so at the checkout counter is actually a zebra stripe type magnet that will de-magnetize the strip when the tag is swiped past it. The reason for this is that many ne'er-do-wells would think think they could defeat the tags by magnetizing them., but would in fact, make sure the tags were fully activated. Also another part of the design is the plastic separator between strips is slippery Teflon, so that the strip can resonate without being too quickly damped.

Thanks for this! I work in retail and have been wondering how those things work for a long time.

Amorphous metals! Love that stuff. Have a piece of a Fe-B alloy that CSIRO were experimenting with in the early 90's...

I learned about this by pranking shopping carts attaching the tags to the underside.