Metal Detector Technology – Three Ways to Go

As with any tool, the final decision will come from a balancing of purpose and cost.

In other words, what do you wish to find? Where will you be looking? And finally, how much are you willing to pay?

The three major technologies are Very Low Frequency (VLF), Pulse Induction (PI), and Beat Frequency Oscillator (BFO).

Very Low Frequency (VLF)

This metal detector technology monitors two electromagnetic fields – the first, generated by the detector – the second from objects in range.

The difference in the frequencies of these two fields is analyzed by the detector to suggest what the object is made of.

The strength of the resulting signal is an indication of the object’s depth.

Pulse Induction (PI)

Objects in range generate a responding electromagnetic field that interferes with the relatively stable value of the detector generated reflective pulse.

While less effective at object identification (discrimination) than the VLF units, the PI detectors are superior in places where the environment itself is highly conductive – underwater, for example.

The PI metal detector technology is also the most accurate at measuring the depth at which an object will be recovered.

Like the VLF units, pulse induction is not the lowest cost alternative.

Beat Frequency Oscillator (BFO)

This is an older, less sophisticated technology that uses a small receiver to monitor radio waves generated by electromagnetic fields produced by the BFO detector’s two coils. The radio signals are converted to an audible tone which is altered in pitch when an object is detected.

Although accuracy and precision are more limited with a BFO unit, this technology is often a good choice for those new to the hobby.