A HACCP audit may identify a risk of various metal types, including ferrous, non-ferrous and stainless steel. However, the sensitivity of the metal detector can vary depending on the type of metal contaminant present. Typically ferrous is the easiest to detect, and stainless steel is the hardest to detect. However, as with many “rules” there are exceptions to this.
There are a number of factors that affect the detection sensitivity of a metal detectionand the ability to find different types of metal. It’s important to understand these factors to get the most out of your metal detection program.
Sensitivity is the measure of a metal detector’s ability to detect a specific type and size of metal contaminant. The better the sensitivity of the metal detector, the smaller the pieces of irregular-shaped metal it can detect. Performance is usually expressed in terms of the diameter of a test sphere made from a specific type of metal, such as ferrous, non-ferrous, aluminum or stainless steel. The higher the sensitivity of the metal detector, the smaller the pieces of metal it can detect. It is a clear ideal, but one that is complicated by a number of factors.
We regularly refer to the diameter of a ball size when discussing detection sensitivity. For example, a highly sensitive detector could detect a 0.6mm ferrous ball. The effect of the ball size is small but real life, metal contaminants can be much larger. Therefore, small changes in detecting ball size can make big changes to the size of metal contaminants that can be found.
How Metal Detector Sensitivity is Measured
When measuring the sensitivity of a metal detector, a test piece must be reliably detectable when passed through the center of the aperture of the metal detector. However, there is a significant difference between the test piece's spherical sensitivity and the actual length of an irregular-shaped or wire-type contaminant that can be detected. A number of factors can affect the sensitivity of a metal detector.
How to Achieve Optimum Operating Sensitivity
To protect consumers, maximize efficiency and meet industry standards, manufacturers and processors have an important role to play in identifying, implementing and maintaining an optimum level of metal detector sensitivity.
METTLER TOLEDO metal detectors have a range of different technologies to suit the product being inspected. For example, the optimum technology for inspecting dry products such as snack foods is our Profile metal detector with ultra high-tuned frequency to deliver exceptional sensitivity to detect more and smaller pieces of metal.
In challenging applications where products are hot, wet, chilled or cooling, our Profile Advantage metal detector with multi-simultaneous frequency and product signal suppression technology is far more effective.
Choosing a stable, reliable metal detector that delivers enhanced sensitivity levels is an integral part of a food safety program to minimize metal contamination.