How to Build a Sensitive Metal Detector


The sensitivity of a metal detector is dependent on the diameter of the search coil or plate. While a search coil of greater diameter will increase the penetration depth of the metal detector the sensitivity of the detector decreases with diameter. The method for building the metal detector described here eliminates the need to determine the most appropriate diameter for the search coil but ensures that the metal detector is sensitive.

Things You'll Need

  • CD case with black insert in the middle
  • AM/FM radio
  • Scientific calculator
  • Nylon straps
  • Strap the AM/FM radio to one side of the central hole of the CD casing bottom using the nylon straps by attaching one end of the nylon straps to the radio and the other to the body of the CD casing. Ensure that the radio fits onto the CD casing bottom and will not obstruct the casing top from being put back on. The radio should be in an upright position facing the hole of the CD casing.

  • Strap the scientific calculator on the other side of the central hole of the CD casing using nylon straps. Strap the calculator in an upright position facing the radio.

  • Tune the radio to the highest AM frequency. You will hear only static at this point. If a channel has been allotted this frequency, tune to the nearest frequency before the radio station.

  • Switch on the calculator and slowly lower the CD casing cover onto the CD casing bottom to close the casing.

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  • Photo Credit metal detecting image by Joy Fera from
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