A metal detector is an electronic equipment which is bought in use to detect the metals. Generally it is bought into use keeps a track of terrorist activities as they keep on implanting and bringing bombs, guns and metal bombs everywhere. A metal detector can detect any form of metal that you carry or hide anywhere and thus it is a great device to check if someone is carrying any form of metal with him or her. There are two types of metal detectors. One is a Very Low Frequency (VLF) metal detector and the other is Pulse Induction (PI) metal detector. The working of metal detectors goes as follows:-
How do the Metal Detectors Work
1. Electromagnetic Field is created:-
There is a transmitter coil fixed with every metal detector which is attached inside the metal detector’s loop. Electric current is driven through it and electromagnetic field gets created. Now, as electromagnetic field induces current in every metal which comes in contact with it, this will serve to be an advantage for us in the metal detection process.
2. Direction of Current Flow Reversed Thousand Times:-
After the transmission of magnetic field from transmitter takes place, direction of supplied current is reversed thousand times in each single second. This is done every single second the current moves from clockwise to anticlockwise direction and thus a magnetic field gets produced.
3. Magnetic Field Produced:-
Now magnetic field gets produced when current flows in a given direction. The polarity of this magnetic field is towards the ground. When current is reversed, the polarity moves out of the ground. The same polarity becomes an advantage for us when a suspected metal comes in the path of this polarity.
4. Changing Magnetic Field Indices Current:-
Changing magnetic field induces current in the metal object hidden nearby and thus this current produces another magnetic field coming from the metal object itself. This happens when a person carrying metal conductor moves from one place to the other place. The metal will get induced with this current and some changes will be seen with its nature. The magnetic field, thus produced in the metal makes us track its location with the help of receiver.
5. Magnetic Field Received:-
There is a receiver coil fixed inside the loop which receives this second magnetic field produced. The effect of transmitted field gets cancelled out and thus the person using metal detector comes to know that there is a metal around. The receiver coil fixed with a metal detector thus gives us the location of metal as a place with maximum magnetic field reported is the place where metal is buried or hidden.
6. The Resulting Signal:-
The resulting field signal always comes delayed than the transmitted signal. The delay is caused by phase shift. The largest phase shift is reported for the metal objects which are primarily inductive, large, and thick in nature. We consider all these factors while detecting a metal. The metal detectors, fixed with railway stations and metro stations follow the same principal.