Metal Detecting Terminology Glossary
The hobby has its own vocabulary. Here are the terms you'll encounter in forums, videos, and conversation with other detectorists.
Detector Terms
VDI (Visual Display Indicator): A number displayed by the detector representing a target's conductivity. Different metals and target sizes produce different VDI numbers. Learning your detector's VDI scale is key to deciding what to dig.
Ground balance: An adjustment that tunes the detector to ignore the mineral content of the soil. Poorly ground-balanced machines produce false signals. Most modern detectors have automatic ground balance; advanced machines offer manual adjustment for difficult soils.
Discrimination: The detector's ability to ignore certain target types (typically iron) based on their electrical properties. Higher discrimination means fewer trash targets but also a higher chance of missing good ones.
Sensitivity: How responsive the detector is. Higher sensitivity detects deeper and smaller targets but also picks up more ground noise and interference.
Threshold: A constant low hum produced by the detector. Changes in the threshold alert you to targets and ground changes. Many detectorists prefer running with an audible threshold rather than silent operation.
Notch: Selectively accepting or rejecting specific segments of the conductivity range. Lets you filter out specific trash targets while still detecting others in nearby ranges.
Target and Signal Terms
Hot rock: A rock with high mineral content that the detector reads as a target. Common in volcanic and metamorphic geology.
Halo effect: Oxidation products from a buried metal object leaching into surrounding soil, creating a larger electromagnetic signature than the object itself. This makes older targets read bigger and deeper than they physically are.
Iron falsing: When corroded iron produces signals that mimic non-ferrous targets, tricking the discriminator.
Wrap-around: When a large iron object's signal wraps around the conductivity scale and reads as a high-conductor (like silver). Big iron can fool even experienced detectorists.
Digging and Site Terms
Plug: The piece of turf cut and lifted to recover a target. Always replace plugs carefully.
Spoil: The loose dirt removed from a hole during recovery.
Plow zone: The top 8-12 inches of soil in agricultural areas, churned by plowing. This is where most detecting finds are made. See farm fields and history.
Honeypot/honey hole: A particularly productive detecting site.
Hammered out / detected out: A site that's been so heavily detected that remaining finds are sparse.
Permission: A site where you have the landowner's approval to detect. See getting permission.
Technology Terms
VLF: Very Low Frequency. The most common detector technology. See VLF vs. PI.
PI: Pulse Induction. An alternative technology best suited for mineralized ground and salt water.
Multi-frequency / SMF: Simultaneous Multi-Frequency. Detectors that transmit multiple frequencies at once. See understanding frequencies.