Since the 9/11 attack, airports, malls, schools, and other establishments and institutions open to the public have been more stringent with their security. Nowadays, it’s not uncommon to see walkthrough metal detectors located at entrance and exit points or security personnel carrying handheld metal detectors, which are also known wands. When used properly and strategically, metal detectors can go a long way in keeping monitored areas safe from potential threats.

Level of Detection
The effectiveness of security metal detectors largely depends on their range of sensitivity.

Level 1 metal detectors are capable of determining the presence of knives and small hand guns. Level 2 metal detectors, on the other hand, can go as far as detecting the presence of handcuffs and razor blades. And as for Level 3 metal detectors, these are capable of detecting the presence of even a single .22 caliber bullet or minute metal shanks.

Some metal detectors are designed for use in other fields. Professional metal detectors, for instance, are utilized for hunting buried treasure. A basic metal detector, on the other hand, can be used in everyday situations for finding misplaced items like house keys, coins, or jewelry. Some are designed to work even underwater.

How Security Metal Detectors Work
The technology used is also another key factor in determining the effectiveness of security metal detectors.

Metal detectors using “very low frequency” or VLF are also referred to as “induction balance” due to their use of transmitters and receivers. These devices create electromagnetic fields and changes in the electromagnetic field are interpreted and relayed to the metal detector in order to determine the presence or absence of metal in the scanned item.

Metal detectors using VLF technology are the type most widely used for security purposes because of their ability to distinguish the different kinds of metals.

Metal detectors utilizing “pulse induction” or PI technology use currents to create yet another field. This time, however, it’s the reverse of what VLF metal detectors create – an opposite magnetic field, to be more specific. The said currents generate reflected pulses and a sample circuit monitors the amount of time in which these pulses last. If it’s longer than usual then it means metal is present.

Finally, there’s BFO or beat-frequency oscillator, a technology that has been pioneered by the Garret company. Metal detectors using BFO technology have oscillators that generate offset pulses. The differences between these pulses are transformed into certain sounds which would then let you know if metal has been detected or not. It may sound complicated, but it’s actually by far the easiest to use.

Terrorism isn’t an easy thing to combat especially in crowded places like airports. Thankfully, advances in technology help minimize the chances of terrorists slipping past security checks. Read on to know the various preventive measures airport security takes to protect its passengers.

How Terminal Metal Detectors Work
Every passenger must pass through the terminal before entering the airport. Posted at this area are several metal detectors that people have to go through as well for a thorough but hands free inspection of their person.

The Use of PI Technology
PI or pulse induction takes the form of coiled wire attached at one side of the arch. This serves as both transmitter and receiver for the metal detector. PI technology is responsible for sending brief but highly powerful pulses through the wire. Every generated pulse creates a magnetic field that will last only for a very short while before suddenly collapse. Another current will pass through the wire, and this is referred to as the reflected pulse. Its appearance is even briefer, lasting no more than thirty microseconds.

This cycle will continue for as long as the metal detector is used. 100 pulses per second are sent on average, but its range is anywhere from 25 to more than a thousand pulses per second, depending on the type of metal detector used.

Detecting the Presence of Metal
When the presence of metal is detected, a reverse magnetic field is created and one that will produce a longer-lasting reflected current. Incorporated in a metal detector is a sampling circuit that is capable of gauging the length of reflected pulses. It will determine if the reflected pulse lasts longer than usual and if it does then it is likely that the presence of metal has been detected.

Relaying the Presence of Metal
Now that the sampling circuit has determined the possible presence of metal, it will then send its analysis to the integrator. This device amplifies and converts the signals into DC (direct current), which is connected to yet another device, the audio circuit. This last device is responsible for emitting that loud beeping sound you hear when the presence of metal has been detected.

Airport security officials will now request the individual in question to remove any metal object he has in his possession. Once all those items have been removed, he will then be asked to pass through the metal detector once more. If the metal detector continues to beep, the airport security official will use a handheld detector this time. The handheld detector shall trace the length of the individual to isolate the source.

Your possessions are also subjected to a similar inspection as they pass through an X-ray machine. It may seem a tedious process, but as most devices used for terrorist attacks are made of metal, it does contribute a lot to your safety while you spend time at the airport.