How do Metal Detectors work?

Nowhere is product integrity more critical than in food, beverage, and pharmaceutical manufacturing. Alongside continuous improvement initiatives, technical and quality teams are focused on minimising the risk of foreign body contamination. Metal remains one of the most common contaminants, which is why manufacturers across these sectors have long relied on specialist metal detection systems as a key control measure.

BALANCED THREE COIL SYSTEM

ENCIRCLING COIL (CUT AWAY)

  • The most widely used metal detection systems have a balanced coil design.
  • The product passes through three coils within the detection head.
  • The central coil acts as the transmitter, generating a magnetic field using an electrical current.
  • This magnetic field induces a current in two outer coils positioned equidistant from the centre.
  • The outer coils monitor for any disturbance in the magnetic field.
  • The induced currents in the first and third coils cancel each other out, as they are wound in opposite directions. This is known as a balanced system.
  • This configuration establishes a stable electromagnetic field, through which the product passes.
  • When a metallic contaminant enters the field, it disrupts the balance.
  • This disturbance generates a measurable electronic signal.
  • The system interprets this signal to trigger an alarm or rejection mechanism.

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