Principles of Operation

Principles of Operation






All metal detection uses the same principle of operation:

  • An electromagnetic field is created by passing current through a coil and transmitted into soil.
  • The electromagnetic field induces electrical current in a metal target.
  • The metal target then produces its own electromagnetic field that is transmitted back to the coil of the detector.
  • The detector senses the electromagnetic field from the metal target and responds with an alarm to the operator.

However, if the ground is mineralised, it too can produce an electromagnetic field and mask the response from the metal target.

Multi Period Sensing (MPS) Technology





To overcome the effects of mineralised soil, Minelab developed technology known as Multi Period Sensing (MPS). The descriptions and diagrams below indicate how this works.

  • MPS produces a series of wide and narrow pulses that are transmitted into the ground from the coil.
  • After each pulse, a metal target will provide a response that will decay over time.
  • If the ground is mineralised, the soil will also provide a response that will decay over time.
  • Through electronic sampling of the decayed responses, it is possible to identify a soil response from a metal target response.
  • Once identified, the F1A4 electronics can eliminate the response from the soil and continue to detect only the response from the metal target without any loss in detector sensitivity.

Using MPS, the F1A4 is capable of:

  • Detecting a Type 72A AP mine at a depth of 15 cm 19 cm in typical lateritic soil condition
  • Detecting a Type PMN-2 AP mine at a depth of 24 cm 27 cm
  • Differentiating between two metal targets that are 10 cm apart.

BiPOLAR Technology

BiPOLAR Technology



Minelab BiPOLAR technology is a variant of MPS technology, in which some of the transmitted pulses have opposite polarity to others. The time-averaged transmit field of a Minelab Bipolar detector is zero, thus minimising the probability of initiating a magnetic influence mine.

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