WHAT’S THAT HUM? NOISE SOURCES THAT CAN IMPACT FOOD METAL DETECTOR SENSITIVITY

Nathan Tankard, Technical Applications Support at Fortress Technology, examines the cause and effect of these disturbances and the measures that can be implemented to reduce noise interference.

Many factors 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 orientation of the product and contaminant as it passes through the detector. However, environmental conditions, such as airborne electrical interference – static, radio or earth loops – vibration, for example moving metal, and temperature fluctuations, such as ovens or cooling tunnels, may also affect performance.

Unique features like Noise Immunity Structure and digital filters which feature on the companyÂ’s digital metal detectors can suppress some of this interference noise, which may otherwise require reducing the sensitivity levels manually.

The most widespread challenge Fortress engineers encounter turns out to be quite a common issue in food factories. Particularly on end-to-end processing lines incorporating robots, bagging, flow wrapping and conveyors. The effects of electromagnetic interference can negatively impact the performance of metal detectors resulting in false detections, false rejections, and consequently increase food safety risks.

“Packaging machines such as flow wrappers and conveyor belts tend to be the biggest cause of ground loop issues due to worn out or loose fixings and rollers” says Nathan.

Finding the source of the problem quickly and accurately is critical, as ongoing interference on automated processing lines can cause service disruptions. Fortress can deploy a sniffer unit to swiftly track the source of nearby EMI and RFI. Like an antenna, the white disc measures wavelengths and can swiftly located the source of the competing frequencies. With this information, engineers can shield, surpress or alter the path of the emissions.

Fortress also offers the option to upgrade to a high voltage oscillator (HVO). For extremely noisy production settings, including highly automated plants, this solution makes the Fortress metal detector the dominant noise source.

User-friendly Fortress features like automated single pass learning and calibration can deliver an accurate system set-up within seconds and eliminate human errors. Additionally, built-in noise immunity structure – included as standard on all Fortress digital metal detectors, can dramatically reduce the effects of external electrical noise, again resulting in fewer false product rejects.

Nathan concludes: “It is impossible to completely eliminate noise interference in production environments. Yet, by taking these precautions and seeking expert guidance, our engineers can significantly reduce the EMI feedback and ensure metal detection performance and sensitivity is not compromised.”