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