Search coils

The search coil is a vital part of your metal detector. It is the flat, typically circular disk, which generates a magnetic field and senses metallic targets in the surrounding environment. It is located at the end of the stem and is connected to the control housing via a cable normally wound around the stem. The size and depth of the magnetic field is determined by the shape and size of the search coil. Understanding the purposes behind the various sizes and shapes of search coils will empower you with the ability to choose the best search-coil for each application.

Search coils generally consist of two internal sets of coiled wires, a Transmit Coil (TX) and a Receive Coil (RX). Mono coils can be different in that one coil acts as  both the TX and the RX. When the detector is turned on, the TX coil generates a  magnetic field in the surrounding space.  When a metallic object is within this generated magnetic field, it will create a distortion in the magnetic field. The RX coil will sense this distortion and send a  signal to the control housing.

Calculation of inductance multiturn round bundle loop with round cross-section (for metal detectors). To calculate the round multiturn wire harness ring, the plug-in multiloop uses the following empirical expression:

   L – inductance (H)
   N – number of turns of the bundle
   d – average diameter of the bundle (m)
   Φ – auxiliary factor, calculated according to the formula and  γ = r/d


The numerical calculation method is the “virtual adding” of turns until the required inductance will be reached. The resulting diameter of the bundle is calculated by the following formula: where:

  dw – wire diameter and    n – the number of turns of the loop, rounded to the nearest larger integer. In the case of a single turn the diameter of the bundle is equal to the diameter of the wire.

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