Metal detectors use electromagnetic induction to detect metal.
In 1881, Alexander Graham Bell constructed a crude metal detector in an attempt to find an assassin's bullet in President James Garfield. Gerhard Fischar patented a portable version in 1931.
In 1881, Alexander Graham Bell constructed a crude metal detector in an attempt to find an assassin's bullet in President James Garfield. Gerhard Fischar patented a portable version in 1931.
Upright "archway" detectors are used at entrances to secured buildings, such as courthouses or airports, to detect metallic weapons which may be brought in. Small portable "wand" detectors are used by security staff to frisk persons for the same. Larger portable metal detectors are used by treasure hunters to locate metallic items, such as jewelry or coins, buried shallowly underground.
There are three types of metal detectors: beat frequency oscillator, induction balance, and pulse induction