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Metal Detectors: How Do They Work

Generally, metal detectors work on the fundamental principle that when electric current pass through a loop it will produce a magnetic field. One of the basic parts of a detector is an oscillator; it will produce the alternating current. Magnetic field is produced when an alternating current or electricity pass through the transmittal coil which is present in metal detectors. So, when a metallic object or a conductor is present close to the coil, it will generate a current in the object that will produce another magnetic field on it. There is another coil in the loop that can be found in detectors that is called the receiver coil that can detect magnetic field changes because of the presence of a metal or a metallic object. The latest metal detectors use these technologies; VLF very low frequency PI pulse induction and BFO beat-frequency oscillator. Let us discuss about these technologies:
Very Low Frequency (VLF) Technology
The most common technology used in metal detectors is VLF. There are coils in sets of two which is the receiver and the transmitter coil. The coil where electric current is sent and creates magnetic fields which constantly push down to the ground and pull back is called the transmitter coil. Magnetic field gets generated by the metal detector which reacts in any metallic or conductor that passes on it. When it encounters the object, the electric current and the magnetic field is formed around the conductor.
In reciprocal, the receiver coil is protected from the influence of the magnetic field which the transmitter coil produces and it is only affected by the conductor and /or the metallic object's magnetic field. The electricity that runs on this receiver coil produces a magnetic field that is weak when a conductor gets near the metal detector. In turn the coil will amplify and send the frequency of the electricity that has the same frequency with the magnetic field that comes from the metal to make analysis in the control box. Through this, the metal detector that works on VLF (very low frequency) will be able to determine disparity among the kinds of metals, the depth of the position when being detected.

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