With security becoming an ever increasing concern in our society, many people wonder if walking through a metal detector is really safe. The quick answer is yes. Metal detectors don’t work the same as X-ray machines which might scan baggage or even your bones at the doctor’s office. Metal detectors work by using low frequency electromagnetic fields. This level has long been considered safe, even for pregnant women. This is also true of the metal detector wands that some places will wave over a person after having triggered a metal detector.
The majority of airport metal detectors work with a technology called pulse induction. These systems have a coiled wire on one side of the unit and act as a transmitter and receiver. A short burst of a current is sent through the wire creating a pulse. When the pulse subsides, the polarity of the magnetic field stops, and it ends with a sharp electrical peak. This peak is very rapid and quickly causes yet another current to travel through the coil. This is called a reflected pulse and is also very quick. This pattern repeats up to 1,000 times per second, depending on the make and model of the unit.
It is possible to tell when a body has something metal on it because the pulse will create an opposite working magnetic field. When the field stops, it causes a reflected pulse, and the metal object takes a longer time to disappear.
A sampling circuit within a metal detector is set to register the length of a given reflected pulse. It then compares the pulse to what it would be registering without any metal, and determines if this new magnetic field is what may be causing the new reflecting pulse to take longer to disappear. It does this in the matter of microseconds and can tell if there is a metal object present.
Multiple Zones in One Unit
Modern metal detectors have several of these coils arranged up and down the body of the unit. This enables the unit to register metal objects from anywhere on a person going through it. It is a more thorough way to detect metal near the head, on the torso, or even on the feet.
The incredibly fast rates at which these indicators work mean people are exposed to no damaging rays whatsoever, making walk-through metal detectors safe.
See more about how to setup and select a walk through metal detector