The most basic way to detect metals is to use BFO technology or pulse frequency oscillator. In a BFO system, there are two cable coils. A long coil is located in the search header and a smaller coil is located in the control box. Each coil is connected to an oscillator that generates thousands of pulses of current per second. The frequency of these pulses is slightly unbalanced between the two coils.

As the current travels through each coil, the general coil transmits radio waves. A small receiver inside the control box picks up the radio waves and creates a series of audible tones (pulses) based on the difference between frequencies. If the coil in the search header passes over a metal, the magnetic field caused by the current flow creates a magnetic field around the object. The magnetic field of the object interferes with the frequency of the radio waves generated by the head coil. As the frequency of the coil frequency in the control box deviates, the audible pulses change in duration and tone.

The simplicity of BFO systems allows them to be manufactured and sold at a very low price. You can even make one at home following the appropriate instructions that can be found on many Internet sites. The only problem is that they do not provide the level of control and precision that VLF and PI systems give us.


The VLF (Very Low Frequency) Metal Detectors, which we commonly use in our prospections have been evolving in terms of their aesthetics and electronics, nowadays these Metal Detectors allow us a much more complete and detailed analysis of the metallic objects that are Finds aware. Discrimination in some of these Metal Detectors is excellent but not perfect, it should be mentioned that there is no Metal Detector in the world that offers perfect discrimination
metal detector accessories
In terms of detection power the VLF have almost no progress, the best Metal Detectors are detecting more or less at the same distance, to get more depth of detection is necessary to increase the emission and reception. The problem is that when you try to increase the signal emission of a VLF to get more depth that begins to deteriorate due to parasitic signals from the ground, which is why the VLF have a limit in terms of depth. The best of these Metal Detectors , as they are already opened, will be able to detect, for example, a coin at a distance no greater than 30cm in a terrain without mineralization.