| The first metal detector was invented by | | | | them. Magnetic field is generated in this |
| Alexander Graham Bell in the year 1881, just | | | | device through the transmitter (high-powered |
| after the invention of telephone in 1876. | | | | coil), getting power from the battery |
| Later, Fischer came out with a portable one | | | | attached. When this electromagnetic field |
| in the year 1931. Today, metal detectors are | | | | penetrates the ground the metals tend to get |
| used in many fields starting from treasure | | | | charged with magnetism. When this happens the |
| hunt to security purposes. These are | | | | coil detects the electromagnetic behaviour |
| electronic devices and are used to locate | | | | and sends a signal to the electronic box. The |
| signs of metal. It is used to search on the | | | | speaker attached to the electronic box beeps |
| ground, people or goods. The materials can be | | | | and the operator hears it and comes to know |
| on the ground may be a piece of iron, | | | | of the presence of metal. The latest |
| aluminum, etc or it can even indicate buried | | | | detectors comprises of microprocessors in the |
| metal could be anything from discarded pieces | | | | electronic box that can give you the type of |
| of aluminum to buried resources. These | | | | metal present. It can measure the time |
| detectors can penetrate various non-metallic | | | | between charging of metal and the receiving |
| substances like soil, wood, sand, etc. | | | | the beep that concludes the type of metal and |
| | | | this length of time is known as phase shift. |
| Metal detectors have electronic boxes with a | | | | There are adjustments in the device when |
| battery case on one end and a handle for the | | | | searching for a particular kind of metal. |
| operative's arm on the other. It has a coil | | | | |
| made of insulated wire wound around a | | | | There are 3 types of metal detectors |
| telescoping shaft that is inside a plastic | | | | following 3 different technologies: |
| disk. The device is held parallel to the | | | | |
| ground due to the angle at which the disk | | | | 1. Beat Frequency Oscillator: Such detectors |
| comes out of the shaft. The electronic box is | | | | have a coil acting as an inductor inside an |
| held in the hand, the power is put on and the | | | | oscillator. With frequency change there is a |
| coil end is slowly swept over the ground. If | | | | change in inductance. There is a second |
| the trace of metal is there on or buried in | | | | oscillator that generates a close frequency. |
| the ground, an electronic beep is heard when | | | | The beeps heard between them indicate the |
| the device sweeps the ground. | | | | presence of metal. |
| | | | |
| The discovery of Electromagnetism was by Hans | | | | 2. Induction Balance Detector: This type has |
| Christian Oersted in the year 1820. It is the | | | | 2 coils that overlie each other. One sends |
| science of combined effect of electric and | | | | waves and the other receives. The two are |
| magnetic field. As stated in wikipedia, | | | | kept adjusted so that when there is absence |
| Electromagnetism is the science of the | | | | of metal they do not indicate or beep. |
| electromagnetic field. That is, a field, | | | | |
| surrounding all of space, which exerts a | | | | 3. Pulse Induction Detector: This type |
| force on those particles that possess the | | | | produces pulses by putting off an indicator. |
| property of electric charge, and is in turn | | | | A coil sends the pulse and the detector |
| affected by the presence and motion of such | | | | searches for echos. |
| particles. | | | | |
| | | | If you have a metal detector, I wish you luck |
| This principle of electromagnetism is on | | | | in finding all kinds of treasures. You never |
| which the Metal detectors work. Since the | | | | know what "rare find" you'll come up with, |
| metals are good conductor of electricity and | | | | and it's fun to look. |
| magnetism, the electromagnetism affects on | | | | |