Detecting More Metal In Challenging Applications

Every product inspected by a metal detector effects the detectors ability to find metallic contaminants. Removing the influence of 'product effect' means even smaller metal contaminants can be found protecting your brand and increasing profit margins.

In the food industry 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 technology's capability to identify that particular contaminant. For metal detection, the extent of this effect normally categorizes products as being either "wet" (showing product effect) or "dry" (not showing product effect).

Metals are not the only materials that have the ability to conduct electricity and generate magnetic fields. There are many naturally high product effect (wet) applications with high moisture or salt content, i.e. fresh meat, chicken, fish and bread. These products are likely to produce a signal in the metal detector in the same way as small metal contaminants would. This makes it difficult for the detector to distinguish between the product and the metal contaminant.

The factors that influence the inspection of wet or high product effect products are:-

1. Moisture content in the product
2. Temperature of the product
3. Size and shape of the product
4. Position and orientation of the product through the detector
5. Consistency or density of the product
6. Packaging material
7. Frequency at which the product is inspected

To compensate for such factors, the sensitivity of metal detectors is lowered, so that the majority of products can pass through the detector without causing false triggering - this means that overall detector sensitivity is reduced.

Traditional metal detectors trade off between the product effect, the maximum operating frequency and metal detector sensitivity. The higher the product effect (the wetter the product), the lower the optimal frequency and the lower the sensitivity of the detector. Conversely, the lower the product effect (the drier the product) is, the higher the operating frequency and detection sensitivity are. Dry products with low product effect have very little impact on the metal detector at high frequencies, so the detector can easily detect very small metal contaminants at these frequencies.

Despite the challenges of product effect, a modernly designed metal detector using the optimum technology will still perform reasonably well. The most sensitive metal detectors on the market operate at more than one frequency simultaneously and are known as Multi-Simultaneous-Frequency (MSF) detectors. They address the problem of product effect in a new and innovative manner.

The new Profile Advantage metal detector uses MSF in combinations of high and low frequencies simultaneously. Built-in product signal suppression technology, two-stage discrimination for frequency and phase cancel the information from these frequency combinations to remove the product signal. This allows for much smaller metal contaminants to be detected. The improvement in detector performance - from the traditional single-frequency metal detectors to the MSF detector - is as much as 50% in product effect or metalized film applications.