Almost every metal detector sold today uses one of two technologies: VLF (very low frequency) or PI (pulse induction). They are not a good and a better version of the same thing. They solve different problems, and buying the wrong one means fighting your machine every time you go out.
The short answer: VLF for most people, most of the time. PI when the ground beats a VLF. Here's how to tell which side of that line you're on. Once you know, browse VLF metal detectors or pulse induction detectors.
A VLF detector transmits and receives continuously through two windings in the coil. Because it is always listening, it can read how a target changes the signal, and that is what gives you target ID numbers, different tones for different metals, and discrimination to ignore trash.
The catch is that the ground talks too. Mineralized soil, black sand and wet salt sand all produce their own signal, and a VLF has to balance that out. On mild ground it does this easily. On very hot ground it struggles, and you end up lowering sensitivity until much of its depth is gone.
A PI detector sends a short, powerful pulse into the ground, switches off, then listens for the echo as it fades. Ground mineralization and salt water fade very quickly, while metal targets hold the signal a little longer. That timing difference lets a PI largely ignore the ground that defeats a VLF.
The trade-off is information. Most PI machines give you little or no discrimination or target ID, so you dig everything: nails, foil and bottle caps along with the good stuff. Many are also heavier, cost more, and are less sensitive to the very smallest targets.
| VLF | Pulse induction | |
|---|---|---|
| Best ground | Parks, fields, dry sand, mild soil | Wet salt sand, black sand, hot mineralized ground |
| Target ID and discrimination | Yes, usually detailed | Little or none |
| Trash handling | Good: skip what you don't want | Poor: you dig everything |
| Depth in hard ground | Drops off sharply | Holds up well |
| Small gold | Strong at high frequency | Weaker on the tiniest pieces |
| Weight and price | Lighter, wider price range | Often heavier and more expensive |
| Learning curve | Beginner friendly | Simple controls, but more digging |
Multi-frequency machines are VLF detectors that transmit several frequencies at once. That lets them cope with wet salt sand and varied ground far better than a single-frequency VLF, while keeping target ID and discrimination. For many beach hunters they close most of the gap with PI. They still won't match a dedicated PI in the very hottest ground, but they are the most versatile choice if you hunt a bit of everything. Browse our multi-frequency metal detectors.
If you already own a VLF, take it to the ground you care about. If it stays steady at a reasonable sensitivity after ground balancing, a VLF is right for you. If it chatters constantly and only settles when you turn sensitivity right down, the ground is beating the technology. That is when a multi-frequency or PI machine earns its price.
Tell us where you hunt and what the ground is like, and we'll tell you which technology fits. Read more in our guides to choosing a gold detector, beach detecting and what each type costs, or call (689) 407-5377, Monday–Friday, 9am–5pm EST.
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