Every time I go into my building at work I have to go through the metal detector, in my pockets I usually have my phone, wallet, AirPods and keys. All of these items except the AirPods trigger the metal detectors but not all the time. My phone triggers it every time without fail, my keys trigger it sometimes but I can go through with my keys even though they are made of metal and at last I have a Tile inside my wallet and that triggers the metal detector. My guess was that anything technology related will always trigger the detector and then after that it calculates the amount of metal compared to the mass going through and if it’s more than the limit it rings. But recently I added a new item to the list, an Apple Watch. And to my surprise I can go through the detector and not trigger it while wearing it which means that not all technology triggers it so know I’m confused again, so how do walk through metal detectors work?
In: Technology
Metal detectors work with magnetic fields. When you bring a conductive object into a magnetic field, it alters the field, and those changes can be detected and measured. Metals can change the field differently than other materials, so machines can be designed to ‘go off’ when particular types of changes occur to the magnetic field it is creating.
There’s a lot of factors that determines how any particular object affects the field, such as its specific materials, size, shape, etc. so they try to calibrate the machine so that it catches important stuff but ignores minor things. And some objects might end up being sort of right on the edge of the detection threshold, so other factors might come into play, like what kind of clothing is around them, and what particular part of the magnetic field they travel through each time.
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