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How do Metal Detectors Work in the Food Industry?

There are a number of things that are synonymous with metal detectors. Security, in all likelihood, sits fairly high on that list, as does activities like beachcombing and searching archaeological sites for historically significant finds.

While these are all admirable uses for this technology, there’s yet another use that many seldom think of, even though it affects most of us on a daily basis. Of course, we’re talking about the use of metal detectors in the food industry.


Why are they needed in the production of food you might ask? Well, it all comes down to the method in which food is manufactured and packaged. By and large, the food manufacturing and processing sector relies on automated machinery to produce inventory at a rate that simply can’t be matched by a human workforce. Products can be mixed, baked, sealed, and packaged in a process that moves so quickly that biological eyes couldn’t possibly ensure that the product is contaminate free. Contamination, by the way, can be at the microscopic level, a fact that renders the human eye as ineffectual as asking a raccoon to solve complex algebraic equations.

Why is it Important to Make Sure Food is Metal Free?

Granted, this question does sound a little silly particularly where larger pieces of metal are concerned. If ingested, large pieces of metal can cause a whole host of problems, not least of all internal bleeding, or a tearing of the stomach or intestine. On the particle level, ingesting metals could lead to varying levels of toxicity within the body which, depending on the metal, can certainly be life threatening.

What Are the Most Common Types of Metal Detectors Used?

It goes without saying that the types of metal detectors that are used in the production of goods destined for human consumption are much more powerful and sophisticated than the handheld variety that can be purchased at your local Radio Shack.

In truth, there are two basic types of detectors that are widely used, each capable of performing slightly different tasks. Detectors equipped with a general search head can detect ferrous and non-ferrous metals (think non-magnetic), as well as stainless steel in frozen or unfrozen, packaged or unpackaged food. Ferrous in-foil detectors are somewhat more limited than its counterpart, as it can only detect ferrous metals contained in food that has been packaged in foil.

How Do They Work?

As we alluded to earlier, industrial metal detectors are sophisticated pieces of machinery. To give you a sense as to just how complex they can be, we’ll take a look at a balanced coil metal detector.

There are three coils that are used in this detection system, all of which are encased in a metal box that protects the delicate instruments from water and fine dust particles. On the outside, there is an aperture, usually made of plastic, through which the material passes and where it is assessed. Of the three coils within the system, one works in much the same way as a radio transmitter, effectively illuminating the metallic particle (even those smaller than can be detected by the human eye) so that it can be detected. The second and third coils act as signal receivers by responding to the various properties of the metal. Illuminated particles only emit one millionth of a volt, so the receiving coils must be incredibly sensitive in order to detect the anomaly. By using a high-powered RF amplifier then modulating it down to a lower frequency, the signals can be digitized for optimal sensitivity.

Magnetic-based systems operate in a much different manner. To put it simply, these systems subject the material to a very strong magnetic field as it passes through a “tunnel”. Any ferrous material becomes magnetized as it passes through, allowing it to be detected by a series of receiver coils. In both cases, this process is completed at incredible speeds.

Without the use of metal detectors in the food industry, the products we all consume couldn’t possibly be as safe as they are. Using this technology, along with many of the other principles that guide manufacturers, we can all rest just a little bit easier knowing that the food we eat is safe.