How to Read Your Metal Detector's Display & Tones
Your detector communicates through audio tones and (on most modern machines) a visual display. Learning to interpret both is the core skill of metal detecting. This takes practice and repetition, but understanding the principles speeds up the learning curve.
Audio Signals
Most detectors use different tone pitches for different target types:
- Low grunts: Iron and low-conductivity targets
- Mid tones: Nickels, pull tabs, foil, small gold jewelry, lead
- High tones: Coins (copper, silver, clad), larger brass items
The key is consistency. A solid, repeatable signal that sounds the same on each swing is more likely to be a real target than a broken, inconsistent signal. Swing over a target from multiple directions — a good target will give a consistent response from all angles. A piece of iron will often give mixed signals depending on swing direction.
VDI Numbers
The VDI (or target ID number) is a numerical representation of the target's conductivity. The scale varies by manufacturer, but the principle is the same: iron reads low, copper and silver read high, and everything else falls somewhere in between. Typical ranges on a 0-99 scale:
- Iron: 0-15
- Foil, tiny targets: 15-25
- Pull tabs, nickels: 25-50
- Zinc pennies, small brass: 50-70
- Copper pennies, silver coins: 70-95
These numbers are approximate and vary significantly by detector model. Build your own reference by testing known targets in your test garden.
When to Dig
Early on, dig everything. Once you've developed confidence in your machine, you can be more selective. But remember: no detector is 100% accurate at target identification. Being too selective means missing finds. Most experienced relic hunters run minimal discrimination and make dig decisions based on the overall character of the signal rather than relying entirely on the VDI number.