Editing Metal detector (section)

===Civil engineering===
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In civil engineering, special metal detectors ([[cover meter]]s) are used to locate [[Rebar|reinforcement bars]] inside walls.

The most common type of metal detector is a hand-held metal detector or [[Electromagnetic coil|coil]]-based detectors using oval-shaped disks with built-in [[copper]] coils. The search coil works as sensing probe and must be moved over the ground to detect potential metal targets buried underground. When the search coil detects metal objects, the device gives an audible signal via speaker or earphone. In most units, the feedback is an [[Analogue electronics|analog]] or digital indicator.

The metal detectors were first invented and manufactured commercially in the [[United States]] by Fisher Labs in the 1930s; other companies like Garrett established and developed the metal detectors in terms of technology and features in the following decades.