is it like magnets? I feel like it’s magnets
In: 4
Not sure if this is entirely right, but I think in it’s most rudimentary form it uses something like two coils. One has an alternating or pulsed current which then produces a magnetic field. The other coil picks that up, which in turn produces a current again. But the trick is measuring the difference at which the oscillations in current changes between the in and out coils. (Albeit with some offset adjustment, because there’s a little bit of hysteresis or lag and energy loss between the two. The idea is to zero that difference via calibration when there’s no other chunk of metal around.)
Now when you put that near some piece of metal, the eddy currents induced in it also produce a field and that changes the rate of change in magnetic fields between in and out coils. So the difference then goes up or down from the zeroed calibration, which is reflected on an visual indicator and/or those squawking noises on an earpiece or headphones.
Then it’s just a matter of sweeping the thing back and forth and figure out where the signal change is centered. Fancier detectors do even more with more refined ways of measuring at specific frequencies or whatever to try finding specific metals, but I think the gist of it.
I’d think there may be other ways to do it as well. Radar/radio based rather than magnetic field changes, but that’s getting fancier still with things like imaging and all that on top. And then those systems look for stuff like different densities and levels of reflectivity of whatever the radio beam is hitting.
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