system
Given the following post, respond as if you're commenting on Reddit:
human
Does the speed at which you pass through a metal detector effect its sensitivity?

*affect

Say I have a 20g iron nail in my pocket, and this is right around the threshold of a metal detector in a security line. Would it matter if I ran through the detector at top speed or walked through the detector slowly? 

In my mind there are two considerations. One, running through may give the detector a short enough signal that the software filters it out as an anomaly (here I'm talking about speeds attainable by humans, I'm not trying to say that the piece of metal is going so fast that it exceeds the sampling rate of the detector, just that there are software controls to exclude false positives but in this case they would be filtering out a true positive.)

Second, going through faster actually will generate a larger signal (like a magnet passing through a coil more quickly generates a larger current), so it's the person who walks through very slowly that is not detected.

I am asking these questions with little understanding of the engineering or physics behind metal detectors, and was hoping you all could provide some insight.
gpt
If the magnetic field of the metal detector were constant, then moving slow enough would not set it off. However, most, if not all metal detectors use oscillating magnetic fields, which you can basically think of as a magnet moving back and forth. In this case, it doesn't matter how you moved.


Addendum: A metal detector works by using an oscillating magnetic field to set up electric currents in a metal. It only works on metals because metals have electrons that can move around freely (that's why they conduct electricity). The electric currents, then in turn set up their own magnetic field. Since the whole thing is driven by the first magnetic field, you look for a second magnetic field that oscillate at the same frequency as that first field to determine if there's metal around.