Metal Detectors

What Is a Metal Detector?

What Is a Metal Detector?

Core Principle

  1. Electromagnetic Induction

    A coil of wire (the transmitter) is energized with an alternating current, creating a fluctuating magnetic field. When this field encounters a conductive object, it induces eddy currents in that object. Those eddy currents generate a secondary magnetic field, which is picked up by a receiver coil.

  2. Signal Processing

    The detector’s electronics compare the transmitted and received signals to distinguish metal targets from background mineralization. When a metal object is detected, the unit alerts the user via audio tones, visual indicators, or both.


Typical Applications

  • Security & Safety: Airports, courthouses, schools, and public events use walk-through detectors to screen for weapons.
  • Hobby & Recreation: Treasure hunters use portable detectors to find coins, jewelry, and artifacts in parks, beaches, or fields.
  • Construction & Utilities: Locate buried pipes, cables, and rebar before excavation.
  • Food & Pharmaceutical Industries: Inline metal detectors ensure no metal contaminants make it into packaged products.
  • Archaeology & Geology: Non-invasive surveying of subsurface features or buried objects.

Strengths & Limitations

Pros:

  • Rapid, non-destructive detection of metal within centimeters to several meters.
  • Portable and flexible deployment.
  • Adjustable sensitivity and discrimination to ignore “trash” metals.

Cons:

  • Cannot detect non-metallic threats or objects.
  • Performance affected by mineralized soil or electromagnetic interference.
  • Depth vs. precision trade-off: larger coils detect deeper but are less precise.