Metalldetektorer

Metalldetektorer are electronic devices designed to locate metallic objects hidden underground, underwater, or inside objects. They consist of a control unit and one or more search coils connected by a cable. They are commonly used by hobbyists, archaeologists, and security personnel.

Principle of operation: The search coil emits an alternating magnetic field. When metal enters the field, eddy currents are generated and create a secondary magnetic field that the detector senses. The resulting signal is processed and translated into audible tones or visual displays indicating a target and its approximate depth.

Types: The most common technologies are very low frequency (VLF) detectors, which use two or more coils to discriminate metals, and pulse induction (PI) detectors, which send short pulses and monitor the returned signals; beat-frequency oscillator (BFO) models. Some devices combine multiple frequencies for greater versatility.

Components and features: Key parts include the search coil, the control box, and the power source. Features may include ground balance to compensate mineralized soil, target discrimination to distinguish junk from desirable metals, waterproof coils, and headphone or speaker outputs.

Applications: Hobbyists search for coins, relics, and precious metals. Archaeologists may use them for survey work where permits allow. In security settings, metal detectors perform screening in airports, courthouses, and events. Industrial uses include locating buried pipes or rebar within concrete and detection of conductive materials in manufacturing.

History and development: Early concepts appeared in the late 19th and early 20th centuries, with practical detectors following in the mid-20th century. Since then, advances in circuitry and materials have produced a wide range of devices tailored to different environments and targets.