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