/// How Security Metal Detectors Work
Security metal detectors are devices that are used to detect the presence of various types of metal.
Metal detectors in security mostly use passive detection, which measures the changes in the Earth’s magnetic field caused by an object.
Metal detectors are an important part of building and area security. By detecting the presence of certain objects, machines and tools, they help to prevent dangerous items from being brought into sensitive and target prone areas then to be used.
How Metal Detectors Work:
Metal detectors work by using a magnetic field to detect the presence of metals. The magnetic field is created by a coil of wire that is wrapped around a metal rod. When the coil of wire is passed over (or crosses over) a metal object, the magnetic field is disturbed and this creates a signal that can be detected by the metal detector.
Metal detectors are usually hand-held devices or walk-through structures that contain sensors that emits an electromagnetic field. When this field comes into contact (within range) with a metal object, the device beeps or vibrates to alert the user.
When this field comes into contact with a metal object, it causes the object to become electrically charged. This charge then interferes with the electromagnetic field, which causes the metal detector to beep or vibrate. The strength (also known as reflections) of the signal will depend on the size and type of metal object that is detected.
These “reflections” will be stronger if there is more (mass, density) metal present. In order to be effective, metal detectors must be tuned to the right frequency as per use and expected weaponology. This ensures that they can discriminate between different types of metal and avoid false positives.
Not all metals will be detected by a metal detector as not all metals give off a magnetic field (or strong enough). Metals such as titanium, copper, brass and aluminum, gold, silver, platinum and palladium.
These metals require active detection (as supposed to the standard passive detection), a metal detector that generates a time-varying magnetic field.
How to Bypass Metal Detectors
Types of Metal Detectors
There are two main types of metal detectors: induction balance and pulse induction. Induction balance detectors are the most common type of detector and use a single coil that both emits and receives the electromagnetic signal.
Pulse induction detectors have two coils: one that emits the signal and one that receives it. These detectors are more expensive but are also more sensitive and can be used in difficult environments.
Where Metal Detectors Are Used
Airports // All airports are equipped with security screenings for passengers and their baggage for weapons or other prohibited items. Airport security staff use handheld metal detectors to perform pat-downs on passengers, and walk-through metal detectors to screen passengers and their carry-on luggage.
Schools // Used in some schools (especially the USA) as a way to prevent students from bringing weapons onto school property. Schools that use metal detectors typically have them at entrances and exits, and may also conduct random searches of students using handheld metal detectors.
Courthouses // Used in essentially all courthouses to screen visitors for weapons before they are allowed entry into the building. Visitors must pass through a walk-through metal detector, and may also be subject to a pat-down search with a handheld metal detector.
Stadiums // Sports / entertainment stadiums use metal detectors to screen fans as they enter the venue. Fans must pass through a walk-through metal detector, and may also have their bags searched by security personnel.
Government Buildings // Such as city halls and state capitols, use metal detectors to screen visitors for weapons before they are allowed entry into the building. Visitors must pass through a walk-through metal detector, and may also be subject to a pat-down search with a handheld metal detector.
Prisons // All prisons use metal detectors to screen visitors for weapons before they are allowed entry into the facility. Visitors must pass through a walk-through metal detector, and may also be subject to a pat-down search with a handheld metal detector.
Power Plants // Most of these types of facilities use metal detectors to screen employees and contractors as they enter the facility. Employees and contractors must pass through a walk-through metal detector, and may also have their bags searched by security personnel.
By understanding how metal detectors work, we can see why they are an essential part of security measures for non-permissive places. And as an operative, this gives us ideas on how to get around such obstacles for when the mission requires it.