Understanding challenging applications for improved metal detection

White paper on metal detection in food and beverage industriesIn the food and pharmaceutical industries many of the products being inspected for contamination exhibit a phenomenon known as ‘Product Effect’. This is where the type of product being inspected, can itself hinder the inspection technologies’ capability to identify a particular contaminant.

Other inspection technologies may refer to this phenomenon differently but for metal detection technology the extent of this effect normally categorises products as being either wet or dry. The purpose of this White Paper from Mettler-Toledo – titled Understanding Challenging Applications for Improved Metal Detection – is to explain what is meant by these terms and also to develop an understanding as to why this is important when choosing the right metal detector to use.

To understand the phenomenon, it is important to know, firstly, how a metal detector works. It will then be clear why this happens and why product effect matters.

At its most basic level, a metal detector consists of three sets of coils that are said to be balanced. These coils are typically made up of copper wire wound around a coil former. The coil former is usually rectangular or round – these are the most common aperture shapes for metal detectors used in the food and pharmaceutical industries. The centre coil is called the transmit coil (Tx) and the outer coils are called receive coils (Rx1 & Rx2). The receive coils are wound in opposite directions to each other, with one end of each coil connected. The product being inspected by the metal detector is passed through the coil former, which is also known as the metal detector aperture.

The metal detector works by transmitting a high-frequency signal into the Tx coil, which generates a magnetic field in the aperture. This magnetic field induces a small voltage into each of the Rx coils. These induced voltages will have reversed polarities, due the fact that the coils are wound in opposite directions. The metal detector’s control electronics measure the difference between the voltages – and for a well-balanced detector, this value should be zero volts. In reality, a metal detector is very seldom perfectly balanced and the control electronics are designed to compensate for small imbalances present when the metal detector is built or changes caused by thermal, mechanical or electromagnetic effects on the coil system. The build quality and auto balance functionality are therefore important considerations when buying a metal detector. A poorly designed or manufactured detector is likely to drift out of balance, which could result in unnecessary downtime, poor performance and/or false triggering.

To download Understanding Challenging Applications for Improved Metal Detection by Mettler-Toledo, click here.

Mettler-Toledo is represented by Microsep in South Africa.

Visit the official COVID-19 government website to stay informed: sacoronavirus.co.za