Airport metal detectors primarily use pulse induction (PI) technology to identify metallic objects on a person.
Here's a breakdown of how they work:
- Pulse Generation: The system sends powerful, short bursts (pulses) of current through a coil of wire located on one side of the archway.
- Magnetic Field Creation: Each pulse generates a brief and intense magnetic field.
- Eddy Current Induction: When a metallic object enters this magnetic field, it induces eddy currents within the metal. Think of it as creating tiny electrical currents within the metal object.
- Magnetic Field Disturbance: These eddy currents then create their own, secondary magnetic field. This secondary field opposes the primary magnetic field generated by the metal detector's coil.
- Detection: The metal detector is extremely sensitive to changes in the magnetic field. It detects the disturbance caused by the metal object's secondary magnetic field.
- Alarm Trigger: If the disturbance exceeds a pre-set threshold, the metal detector triggers an alarm (usually a beep or a light).
In simpler terms: The metal detector sends out a magnetic field. If metal passes through that field, it changes the field, and the detector notices the change and sounds the alarm.
While some older systems may utilize continuous wave (CW) technology, the robustness and sensitivity of PI systems have made them the standard in airport security.
