The most widely used type of metal detector in the food industry functions on the principle known as the ‘balanced coil’. With a general-purpose search head, these can detect ferrous, non-ferrous metals and stainless steels in fresh and frozen products, whether unwrapped, wrapped, or in metallized films. Yet, unlike metal detectors designed for specific applications, these general-purpose search heads are still unable to detect every particle of metal passing through them. For optimal performance and sensitivity, the search head should be sized appropriately to the product being inspected.
Many factors will determine the theoretical sensitivity of a metal detector. Among them are the aperture size (the smaller the aperture, the smaller the piece of metal that can be detected), the type of metal, product effect, and the type and orientation of the contaminant as it passes through the detector. Environmental conditions, such as airborne electrical interference - static, radio or earth loops - vibration and temperature fluctuation may also affect performance.