Glossary
What is Metal detector (food)?
Also called: food metal detector, inline metal detector
A food metal detector is an inspection machine that senses metal in product or packs as they pass through its aperture and triggers their removal from the line.
Most food metal detectors use a balanced three-coil design: a transmitter coil between two receiver coils around the aperture that product passes through. With no metal present, the receiver signals cancel out. A metal fragment upsets that balance, and the amplified signal triggers a reject device.
Detectors are often placed after packaging, so nothing can enter the pack after inspection. Sensitivity is stated separately for ferrous, non-ferrous and stainless steel test pieces. Wet or salty products produce their own signal, called product effect, so detectors are set up and tested on real product. A standard balanced-coil detector cannot inspect product in aluminium foil or foil trays: inspect it before packing, or use a ferrous-in-foil detector or X-ray. Metallised film needs a compensated detector, or a free-fall detector before packing. Detectors are often paired with a checkweigher.